12th Std Science Lesson Wise Questions in English – Part 2

12th Science Lesson 7 Questions in English

7] Current Electricity

1. Which among the following constitutes motion of charges?

1. Electric current
2. Electro statics
3. Electric void
4. All the above

Explanation

The motion of charges constitutes ‘electric current’. In reality, the charges are always moving within the materials. For example, the electrons in a copper wire are never at rest and are continuously in random motion. Therefore, it is important to analyse the behaviour of charges when they are in motion.

2. Current electricity owes its origin to whom?

1. Michael Faraday
2. Alessandro Volta
3. Georg Ohm
4. Thomas Edison

Explanation

Current electricity is the study of flow of electric charges. It owes its origin to Alessandro Volta (1745-1827), who invented the electric battery which produced the first steady flow of electric current. Modern world depends heavily on the use of electricity. It is used to operate machines, communication systems, electronic devices, home appliances etc., In this unit, we will study about the electric current, resistance and related phenomenon in materials.

3. Which among the following statement is correct

1. Atom is made up of matters. Each atom consists of a negatively charged electrons with positively charged nucleus moving around. Atoms in metals have one or more electrons which are loosely bound to the nucleus. These electrons are called valid electrons and can be easily detached from the atoms.
2. The substances which have an abundance of these free electrons are called conductors. These free electrons move randomly throughout the conductor at a given temperature. In general due to this random motion, there is no net transfer of charges from one end of the conductor to other end and hence no current in the conductor.
3. When a potential difference is applied by the battery across the ends of the conductor, the free electrons drift towards the positive terminal of the battery, producing a net electric current.
4. Both 1 and 2
5. Both 1 and 3
6. Both 2 and 3
7. All 1, 2 and 3

Explanation

Matter is made up of atoms. Each atom consists of a positively charged nucleus with negatively charged electrons moving around the nucleus. Atoms in metals have one or more electrons which are loosely bound to the nucleus. These electrons are called free electrons and can be easily detached from the atoms.

4. Which among the following statement is correct?

1. The mass move from lower gravitational potential to higher gravitational potential
2. The mass move from higher gravitational potential to lower gravitational potential
3. The mass move from lower gravitational potential to higher gravitational potential as well as higher to lower gravitational potential
4. Positive charge flows from region of lower electric potential to region of higher electric potential

Explanation

We know that the mass move from higher gravitational potential to lower gravitational potential. Likewise, positive charge flows from region of higher electric potential to region of lower electric potential and negative charge flows from region of lower electric potential to region of higher electric potential. So, battery or electric cell simply creates potential difference across the conductor.

5. Which in a conductor is defined as the rate of flow of charges through a given cross-sectional area A?

1. Electric resistance
2. Electric potential
3. Electric capacitance
4. None of the above

Explanation

The electric current in a conductor is defined as the rate of flow of charges through a given cross-sectional area A.

6. If a net charge Q passes through any cross section of a conductor in time t, then the current is defined as _____

1. I = Q × t
2. I = Q / t
3. I = Q t
4. I = Q ̶ t

Explanation

If a net charge Q passes through any cross section of a conductor in time t, then the current is defined as I = Q / t. But charge flow is not always constant. Hence current can more generally be defined as I_avg = / Δt.

7. Compute the current in the wire if a charge of 120 C is flowing through a copper wire in 1 minute?

1. 1A
2. 2A
3. 3A
4. 5A

Explanation

The current (rate of flow of charge) in the wire is I = Q / t = 120 / 60 = 2A.

8. Which among the following statement is correct regarding conventional current?

1. In an electric circuit, arrow heads are used to indicate the direction of flow of current. By convention, this flow in the circuit should be from the positive terminal of the battery to the negative terminal. This current is called the conventional current or simply current and is in the direction in which a positive test charge would move.
2. In typical circuits the charges that flow are actually electrons, from the negative terminal of the battery to the positive terminal. As a result, the flow of electrons and the direction of conventional current point in opposite direction. Mathematically, a transfer of positive charge is the same as a transfer of negative charge in the opposite direction.
3. Only 1
4. Only 2
5. Both 1 and 2
6. None

9. Which produces enormous electric current in a short time in Nature?

1. Tide
2. Lightning
3. Tornado
4. Dune

Explanation

Electric current is not only produced by batteries. In nature, lightning bolt produces enormous electric current in a short time. During lightning, very high potential difference is created between the clouds and ground and hence charges flow between the clouds and ground.

10. Which among the following statement is correct

1. In a conductor the charge carriers are free electrons. These electrons move freely through the conductor and collide repeatedly with the negative ions. If there is electric field, the electrons move in random directions, and hence their velocities are also randomly oriented.
2. On an average, the number of electrons travelling in any direction will be equal to the number of electrons travelling in the opposite direction. As a result, there is no net flow of electrons in any direction and hence there will not be any current. Suppose, a potential difference is set across the conductor by connecting a battery, an electric field is created in the conductor.
3. This electric field exerts a force on the electrons, producing a current. The electric field accelerates the electrons, while ions scatter the electrons and change their direction of motion. Thus, we see zigzag motion of electrons. In addition to the zigzag motion due to the collisions, the electrons move slowly along the conductor in a direction opposite to that of
4. Both 1 and 2
5. Both 1 and 3
6. Both 2 and 3
7. All 1, 2 and 3

Explanation

In a conductor the charge carriers are free electrons. These electrons move freely through the conductor and collide repeatedly with the positive ions. If there is no electric field, the electrons move in random directions, and hence their velocities are also randomly oriented.

11. Which is the average velocity acquired by the electrons inside the conductor when it is subjected to an electric field?

1. Conductor velocity
2. Ion velocity
3. Compromised velocity
4. Drift velocity

Explanation

The drift velocity is the average velocity acquired by the electrons inside the conductor when it is subjected to an electric field.

12. The average time between two successive collisions is called _____

1. Mean shift time
2. Mean crap time
3. Mean free time
4. Mean slide time

Explanation

The average time between two successive collisions is called the mean free time denoted by τ. The acceleration ρ a experienced by the electron in an electric field is given by

= ( ̶ e ) / m [since = ( ̶ e ) ]

13. Which among the following equation gives drift velocity?

1. v_d = a τ
2. v_d = a / τ
3. v_d = a × τ
4. v_d = a + τ

Explanation

The drift velocity v_d is given by v_d = a τ.

v_d = E = −µE

14. Which is defined as the magnitude of the drift velocity per unit electric field?

1. Mobility of the electron
2. Charges of the electron
3. Capacity of the electron
4. Fixture of the electron

Explanation

Here µ = e τ / m is the mobility of the electron and it is defined as the magnitude of the drift velocity per unit electric field.

µ = v_d / E

15. What is the SI unit of mobility?

1. m² V s
2. m² V s^-1
3. m² V^-1 s^-1
4. m² V^-2 s^-1

Explanation

The SI unit of mobility is m² V^-1 s^-1

16. The typical drift velocity of electrons in the wire is _____

1. 10^–4 m s^–2
2. 10^–4 m s^–1
3. 20^–2 m s^–1
4. 10^–2 m s^–1

Explanation

The typical drift velocity of electrons in the wire is 10^–4 m s^–1

17. If an electric field of magnitude 570 N C^–1, is applied in the copper wire, find the acceleration experienced by the electron?

1. a = 1.001 × 10¹⁰ m s^–1
2. a = 2.001 × 10¹⁰ m s^–2
3. a = 1.001 × 10¹⁴ m s^–2
4. a = 2.001 × 10¹⁸ m s^–2

Explanation

E = 570 N C^–1, e = 1.6 × 10^–19 C, m = 9.11 × 10^–31 kg

F = ma = eE

a = eE / m = (570 × 1.6 × 10^–19) / 9.11 × 10^–31

= 912 × 10^–19 × 10³¹ / 9.11

a = 1.001 × 10¹⁴ m s^–2

18. Which among the following statement is correct regarding Microscopic model of current?

1. Consider a conductor with area of cross section A and let an electric field E be applied to it from right to left. Suppose there are n electrons per unit volume in the conductor and assume that all the electrons move with the same drift velocity v_d
2. The drift velocity of the electrons = v_d. If the electrons move through a distance dx within a small interval of dt, then v_d = dx/dt; dx = v_d dt [Eqn 1]. Since A is the area of cross section of the conductor, the electrons available in the volume of length dx is = volume × number of electrons per unit volume = Adx × n [Eqn 2]
3. By substituting dx from equation 1 in 2 we get = (A v_d dt) n. Total charge in the volume element dQ = (charge) × (number of electrons in the volume element). dQ = (e)(Av_d dt)n. Hence the current I = dQ / d. I = n e A v_d.
4. Both 1 and 2
5. Both 1 and 3
6. Both 2 and 3
7. All 1, 2 and 3

19. Which is defined as the current per unit area of cross section of the conductor?

1. Slide density
2. Current density
3. Potential difference
4. Point volt

Explanation

The current density ( J ) is defined as the current per unit area of cross section of the conductor.

J = I / A = (n e A v_d) / A

J = n e v_d

20. What is the SI unit of current density?

1. A m^–2
2. A m^–1
3. A m
4. A^–1 m^–1

Explanation

The S.I unit of current density is A / m² (or) A m^–2

21. In general, the current density equation is given as,_____

1. J = σ E
2. J = σ / E
3. J = σ E²
4. J = σ E^–2

Explanation

In general, the current density is a vector quantity and it is given by J = n e v_d. But conventionally, we take the direction of (conventional) current density as the direction of electric field. So the equation becomes J = σ E.

22. Which among the following equation is called conductivity

1. σ = n e² τ m
2. σ = (n e²) / m τ
3. σ = n e² τ m²
4. σ = (n e² τ) / m

Explanation

The equation σ = (n e² τ) / m is called conductivity.

23. The inverse of conductivity is called _____

1. Capacity
2. Resistivity
3. Voltage
4. None of the above

Explanation

The inverse of conductivity is called resistivity (ρ). Ρ = 1 / σ = m / (n e² τ).

24. A copper wire of cross-sectional area 0.5 mm² carries a current of 0.2 A. If the free electron density of copper is 8.4 × 10²⁸ m^–3 then compute the drift velocity of free electrons?

1. v_d = 0.03 × 10^–3 m s^–1
2. v_d = 0.06 × 10^–3 m s^–1
3. v_d = 0.09 × 10^–3 m s^–1
4. v_d = 1.2 × 10^–3 m s^–1

Explanation

The relation between drift velocity of electrons and current in a wire of cross-sectional area A is

v_d = I / neA = 0.2 / (8.4 × 10²⁸ × 1.6 × 10⁻¹⁹ × 0.5 × 10⁻⁶)

v_d = 0.03 × 10^–3 m s^–1.

25. Which among the following statement is correct

1. Current is vector and current density is scalar
2. Current is scalar and current density is vector
3. Both current and current density is scalar
4. Both current and current density is vector

Explanation

In general, the current I is defined as the scalar product of the current density and area vector in which the charges cross. Current density is a vector but current is a scalar. The current I can be positive or negative depending on the choice of the unit vector normal to the surface area A.

26. Determine the number of electrons flowing per second through a conductor, when a current of 32 A flows through it?

1. n = 2 × 10¹⁰ electrons
2. n = 2 × 10²⁰ electrons
3. n = 4 × 10¹⁰ electrons
4. n = 4 × 10²⁰ electrons

Explanation

I = 32 A, t = 1 s

Charge of an electron, e = 1.6 × 10^–19 C

The number of electrons flowing per second, n =?

I = q / t = ne / t

n = It / e = 32 ×1/ (1.6 × 10^–19) = 20 × 10¹⁹ = 2 × 10²⁰ electrons.

27. The ohm’s law can be derived from which among the following equation?

1. J = σ E
2. ρ = 1/ σ
3. I = n e A v_d
4. All the above

Explanation

The ohm’s law can be derived from the equation J = σ E. Consider a segment of wire of length l and cross-sectional area A. When a potential difference V is applied across the wire, a net electric field is created in the wire which constitutes the current in the wire. For simplicity, we assume that the electric field is uniform in the entire length of the wire, then the potential difference (voltage V) can be written as V = El.

28. Which among the following quantity is called resistance of the conductor?

1. V / l
2. σ A
3. 1 / σ A
4. 1 / V l

Explanation

The quantity 1 / σ A is called resistance of the conductor and it is denoted as R. The resistance is directly proportional to the length of the conductor and inversely proportional to area of cross section. Therefore, the macroscopic form of ohm’s law can be stated as V = I R.

29. Which is the ratio of potential difference across the given conductor to the current passing through the conductor?

1. Capacitance
2. Conductance
3. Voltage
4. Resistance

Explanation

The resistance is the ratio of potential difference across the given conductor to the current passing through the conductor. R = V / I.

30. What is the SI unit of resistance?

1. Joule
2. Pascal
3. Ohm
4. Newton

Explanation

The SI unit of resistance is ohm (Ω). The graph between current versus voltage is straight line with a slope equal to the inverse of resistance R of the conductor.

31. A potential difference across 24 Ω resistor is 12 V. What is the current through the resistor?

1. 0.5 A
2. 2 A
3. 288 A
4. 12 A

Explanation

V = 12 V and R = 24 Ω

Current, I =?

From Ohm’s law, I = V / R = 12 / 24 = 0.5 A.

32. An electric cell converts which energy into electrical energy to produce electricity?

1. Heat energy
2. Chemical energy
3. Wind energy
4. Mechanical energy

Explanation

An electric cell converts chemical energy into electrical energy to produce electricity. It contains two electrodes (carbon and zinc) immersed in an electrolyte (sulphuric acid).

33. Which among the following statement is correct?

1. Several electric cells connected together form a battery. When a cell or battery is connected to a circuit, electrons flow from the negative terminal to the positive terminal through the circuit.
2. By using chemical reactions, a battery produces potential difference across its terminals. This potential difference provides the energy to move the electrons through the circuit. Commercially available electric cells and batteries.
3. Only 1
4. Only 2
5. Both 1 and 2
6. None

34. Which among the following statement is correct

1. A battery or cell is called a source of electromotive force (emf). The term ‘electromotive force’ is a misnomer since it does not really refer to a force but describes a potential difference in volts. The emf of a battery or cell is the voltage provided by the battery when no current flows in the external circuit.
2. Electromotive force determines the amount of work a battery or cell has to do move a certain amount of charge around the circuit. It is denoted by the symbol ε. An ideal battery has zero internal resistance and the potential difference (terminal voltage) across the battery equals to its emf.
3. In reality, the battery is made of electrolyte than electrodes, there is resistance to the flow of charges within the battery. This resistance is called external resistance r. For a real battery, the terminal voltage is equal to the emf of the battery. A freshly prepared cell has low internal resistance and it increases with ageing.
4. Both 1 and 2
5. Both 1 and 3
6. Both 2 and 3
7. All 1, 2 and 3

Explanation

In reality, the battery is made of electrodes and electrolyte, there is resistance to the flow of charges within the battery. This resistance is called internal resistance r. For a real battery, the terminal voltage is not equal to the emf of the battery. A freshly prepared cell has low internal resistance and it increases with ageing.

35. The emf of cell ε is measured by what?

1. Ammeter
2. Anemometer
3. Voltmeter
4. Hygrometer

Explanation

The emf of cell ε is measured by connecting a high resistance voltmeter across it without connecting the external resistance R. Since the voltmeter draws very little current for deflection, the circuit may be considered as open. Hence the voltmeter reading gives the emf of the cell.

36. What is the SI unit of electrical resistivity?

1. Ohm
2. Ohm metre
3. Ohm metre²
4. Metre²

Explanation

The electrical resistivity of a material is defined as the resistance offered to current flow by a conductor of unit length having unit area of cross section. The SI unit of ρ is ohm-metre (Ω m).

37. Which among the following is the semiconductor?

1. Fused Quartz
2. Silver
3. Tungsten
4. Germanium

Explanation

The germanium and silicon are semiconductor. Their resistivity, ρ (Ω m) at 20⁰ C 0.46 and 640.

38. Which among the following is not the conductor?

1. Tungsten
2. Pure water
3. Aluminium
4. Copper

Explanation

Pure water is insulator. Other insulators are glass, hard rubber, NaCl, Fused Quartz.

39. When two or more resistors are connected end to end, they are said to be in ____

1. Series
2. Parallel
3. Perpendicular
4. Both series and parallel

Explanation

When two or more resistors are connected end to end, they are said to be in series. The resistors could be simple resistors or bulbs or heating elements or other devices.

40. Which among the following statement is correct

1. Resistors are in parallel when they are connected across the same potential difference. In this case, the total current I that leaves the battery is split into three separate components. Let I₁, I₂ and I₃ be the current through the resistors R₁ , R₂ and R₃ respectively.
2. Due to the conservation of charge, total current in the circuit I is equal to sum of the currents through each of the three resistors. Since the voltage across each resistor is the same, applying Ohm’s law to each resistor, we have I₁ = V/R_1, I₂ = V/R₂, I₃ = V/R_3. Thus, we get 1/R_p = 1/R₁ + 1/R₂ + 1/R₃.
3. Here R_P is the equivalent resistance of the parallel combination of the resistors. Thus, when a number of resistors are connected in parallel, the sum of the reciprocals of resistance of the individual resistors is more than the reciprocal of the effective resistance of the combination. The value of equivalent resistance in parallel connection will be grater than each individual resistance.
4. Both 1 and 2
5. Both 1 and 3
6. Both 2 and 3
7. All 1, 2 and 3

Explanation

Here R_P is the equivalent resistance of the parallel combination of the resistors. Thus, when a number of resistors are connected in parallel, the sum of the reciprocals of resistance of the individual resistors is equal to the reciprocal of the effective resistance of the combination. The value of equivalent resistance in parallel connection will be lesser than each individual resistance.

41. Carbon resistors consists of a which core, on which a thin layer of crystalline carbon is deposited?

1. Glass
2. Aluminium
3. Ceramic
4. Gold

Explanation

Carbon resistors consists of a ceramic core, on which a thin layer of crystalline carbon is deposited. These resistors are inexpensive, stable and compact in size. Colour rings are used to indicate the value of the resistance.

42. In three coloured ring which ring indicates the decimal multiplier after them?

1. First
2. Second
3. Third
4. Both first and third

Explanation

Three coloured rings are used to indicate the values of a resistor: the first two rings are significant figures of resistances; the third ring indicates the decimal multiplier after them.

43. What is the tolerance of carbon resistors if there is no fourth ring?

1. 5%
2. 10%
3. 15%
4. 20%

Explanation

Three coloured rings are used to indicate the values of a resistor: the first two rings are significant figures of resistances, the third ring indicates the decimal multiplier after them. The fourth colour, silver or gold, shows the tolerance of the resistor at 10% or 5%. If there is no fourth ring, the tolerance is 20%.

44. Which among the following statement is correct

1. The resistivity of a material is dependent on temperature. It is experimentally found that for a wide range of temperatures, the resistivity of a conductor increases with decrease in temperature according to the expression. Ρ_T = ρ₀ [1 + α(T ̶ T₀ )]
2. Where ρ_T is the resistivity of a conductor at T^oC, ρ_o is the resistivity of the conductor at some reference temperature T_o (usually at 20^o C) and α is the temperature coefficient of resistivity. It is defined as the ratio of increase in resistivity per degree rise in temperature to its resistivity at T_o. α = ∆ρ/ ρ_o∆T
3. Only 1
4. Only 2
5. Both 1 and 2
6. None

Explanation

The resistivity of a material is dependent on temperature. It is experimentally found that for a wide range of temperatures, the resistivity of a conductor increases with increase in temperature according to the expression, Ρ_T = ρ₀ [1 + α (T ̶ T₀)].

45. Which among the following statement is correct?

1. For conductors α is negative. If the temperature of a conductor decreases, the average kinetic energy of electrons in the conductor increases. This results in more frequent collisions and hence the resistivity decreases.
2. Even though, the resistivity of conductors like metals varies linearly for wide range of temperatures, there also exists a non-linear region at very low temperatures. The resistivity approaches some finite value as the temperature approaches absolute zero.
3. For semiconductors, the resistivity decreases with increase in temperature. As the temperature increases, more electrons will be liberated from their atoms. Hence the current increases and therefore the resistivity decreases.
4. Both 1 and 2
5. Both 1 and 3
6. Both 2 and 3
7. All 1, 2 and 3

Explanation

For conductors α is positive. If the temperature of a conductor increases, the average kinetic energy of electrons in the conductor increases. This results in more frequent collisions and hence the resistivity increases.

46. A semiconductor with a negative temperature coefficient of resistivity is called _____

1. Thermionic
2. Thermistor
3. Thermoform
4. Thermite

Explanation

A semiconductor with a negative temperature coefficient of resistivity is called a thermistor. The electrical conductivity, σ = ne² τ / m. As the resistivity is inverse of σ, it can be written as ρ = m / ne²τ

47. Which among the following statement is correct

1. The resistivity of materials is inversely proportional to the number density (n) of the electrons.
2. The resistivity of materials is inversely proportional to the average time between the collisions (τ).
3. The resistivity of materials is directly proportional to the number density (n) of the electrons.
4. Both 1 and 2
5. Both 1 and 3
6. Both 2 and 3
7. All 1, 2 and 3

48. In which among the following, if the temperature increases, the average time between the collision (τ) decreases and n is independent of temperature?

1. Insulator
2. Metal
3. Semi-conductor
4. All the above

Explanation

In metals, if the temperature increases, the average time between the collision (τ) decreases and n is independent of temperature. In semiconductors when temperature increases, n increases and τ decreases, but increase in n is dominant than decreasing τ, so that overall resistivity decreases.

49. The resistance of certain materials become zero below certain temperature Tc. This temperature is known as _____

1. Critical temperature
2. Super temperature
3. Point temperature
4. Collide temperature

Explanation

The resistance of certain materials become zero below certain temperature Tc. This temperature is known as critical temperature or transition temperature.

50. The materials which exhibit critical temperature or transition temperature property are known as _____

1. Semiconductor
2. Superconductor
3. Insulator
4. None of the above

Explanation

The materials which exhibit critical temperature or transition temperature property are known as superconductors. This phenomenon was first observed by Kammerlingh Onnes in 1911.

51. Kammerlingh Onnes found that which element exhibits superconductor behaviour at 4.2 K. Since R = 0, current once induced in a superconductor persists without any potential difference?

1. Lead
2. Tin
3. Uranium
4. Mercury

Explanation

Kammerlingh Onnes found that mercury exhibits superconductor behaviour at 4.2 K. Since R = 0, current once induced in a superconductor persists without any potential difference.

52. If the resistance of coil is 3 Ω at 20⁰ C and α = 0.004/⁰ C then determine its resistance at 100⁰ C?

1. R₁₀₀ = 1.26 Ω
2. R₁₀₀ = 2.41 Ω
3. R₁₀₀ = 3.96 Ω
4. R₁₀₀ = 4.72 Ω

Explanation

R₀ = 3 Ω, T = 100⁰ C, T0 = 20⁰ C

α = 0.004/⁰ C, R_T=?

R_T = R₀ (1 + α (T-T₀))

R₁₀₀ = 3(1 + 0.004 × 80)

R₁₀₀ = 3.96 Ω.

53. Resistance of a material at 20⁰ C and 40⁰ C are 45 Ω and 85 Ω respectively. Find its temperature coefficient of resistivity.

1. α = 0.044 per^o C
2. α = 0.192 per^o C
3. α = 1.074 per^o C
4. α = 2.840 per^o C

Explanation

T₀ = 20 ⁰ C, T = 40 ⁰ C, R₀ = 45 Ω, R= 85 Ω

α = = = 1/45 (2)

α = 0.044 per^o C

54. Which among the following statement is correct

1. When a battery is connected between the ends of a conductor, a current is established. The battery is supplying energy to the device which is connected in the circuit. Consider a circuit in which a battery of voltage V is connected to the resistor.
2. Assume that a positive charge of dQ moves from point a to b through the battery and moves from point c to d through the resistor and back to point a. When the charge moves from point a to b, it gains potential energy dU = V.dQ and the chemical potential energy of the battery decreases by the same amount.
3. When this charge dQ passes through resistor it loses the potential energy dU = V.dQ due to collision with atoms in the resistor and again reaches the point a. This process occurs continuously till the battery is connected in the circuit. The rate at which the charge loses its electrical potential energy in the resistor can be calculated.
4. Both 1 and 2
5. Both 1 and 3
6. Both 2 and 3
7. All 1, 2 and 3

55. The electrical power produced (dissipated) by a resistor is ____

1. IR
2. I²R
3. I²R²
4. I/R

Explanation

The electrical power produced (dissipated) by a resistor is I² R. It depends on the square of the current. Hence, if current is doubled, the power will increase by four times. Similar explanation holds true for voltage also.

56. Using which law power delivered to the resistance R is expressed in other forms like P = IV = I (IR) = I² R?

1. Faradays law
2. Pascal law
3. Ohms law
4. Newtons law

Explanation

Using Ohm’s law, power delivered to the resistance R is expressed in other forms P = IV = I (IR) = I ² R and P = IV = (V/R) V = V² / R.

57. If the power is in watts and the time is in seconds, the energy will be in ____

1. Ohms
2. Joules
3. Newton
4. Kilowatt

Explanation

The total electrical energy used by any device is obtained by multiplying the power and duration of the time when it is ON. If the power is in watts and the time is in seconds, the energy will be in joules.

58. In practice, electrical energy is measured in ____

1. Kilojoule hour
2. Kilowatt hour
3. Kilo pascal
4. Watt / hour

Explanation

In practice, electrical energy is measured in kilowatt hour (kWh). 1 kWh is known as 1 unit of electrical energy. (1 kWh = 1000 Wh = (1000 W) (3600 s) = 3.6 × 10⁶ J)

59. Which among the following statement is correct

1. The Tamil Nadu Electricity Board is charging for the amount of energy you use and not for the power. A current of 1A flowing through a potential difference of 1V produces a power of 1W.
2. The Tamil Nadu Electricity Board is charging for the amount of power you use and not for the energy. A current of 1A flowing through a potential difference of 1V produces a power of 0.5W
3. Only 1
4. Only 2
5. Both 1 and 2
6. None

60. When current flows through a resistor, some of the electrical energy delivered to the resistor is converted into heat energy and it is dissipated. This heating effect of current is known as ____

1. Newtons heating effect
2. Joules heating effect
3. Pascal heating effect
4. Ohms heating effect

Explanation

When current flows through a resistor, some of the electrical energy delivered to the resistor is converted into heat energy and it is dissipated. This heating effect of current is known as Joule’s heating effect.

61. Which among the following statement is correct

1. Due to internal resistance r of the cell, the voltmeter reads a value V, which is less than the emf of cell ε. It is because, certain amount of voltage (Ir) has dropped across the internal resistance r. Then V = ε – Ir. ie., Ir = ε – V
2. Dividing V = IR in Ir = ε – V, we get r = [(ε – V)/V] R. Since ε, V and R are known, internal resistance r can be determined. We can also find the total current that flows in the circuit. Due to this internal resistance, the power delivered to the circuit is not equal to power rating mentioned in the battery.
3. For a battery of emf ε, with an internal resistance r, the power delivered to the circuit of resistance R is given by P = Iε = I (V + Ir). Here V is the voltage drop across the resistance R and it is equal to IR. Therefore, P = I (IR +Ir) i.e., P = I² R + I² r.
4. Both 1 and 2
5. Both 1 and 3
6. Both 2 and 3
7. All 1, 2 and 3

62. Which among the following statement is correct

1. In P = I² R + I² r, I²r is the power delivered to the internal resistance and I 2 R is the power delivered to the electrical device (here it is the resistance R).
2. For a good battery, the internal resistance r is very small, then I ² R << I ² r and almost entire power is delivered to the external resistance.
3. Only 1
4. Only 2
5. Both 1 and 2
6. None

Explanation

For a good battery, the internal resistance r is very small, then I ² r << I ² R and almost entire power is delivered to the external resistance.

63. A battery has an emf of 12 V and connected to a resistor of 3 Ω. The current in the circuit is 3.93A. Calculate (a) terminal voltage and the internal resistance of the battery.

1. V = 7.12V, r = 0.01 Ω
2. V = 9.83V, r = 0.40 Ω
3. V = 11.79V, r = 0.05 Ω
4. V = 14.51V, r = 0.08 Ω

Explanation

The terminal voltage of the battery is equal to voltage drop across the resistor

V = IR = 3.93 × 3 = 11.79 V

The internal resistance of the battery,

r = [(ε – V)/V] R = [(12 – 11.79) / 11.79] 3

= 0.05 Ω.

64. Which among the following statement is correct

1. Several cells can be connected to form a battery. In series connection, the negative terminal of one cell is connected to the positive terminal of the second cell, the negative terminal of second cell is connected to the positive terminal of the third cell and so on. The free positive terminal of the first cell and the free negative terminal of the last cell become the terminals of the battery.
2. Suppose n cells, each of emf ε volts and internal resistance r ohms are connected in series with an external resistance R. By Ohm’s law, the current in the circuit is I = total emf / total resistance = n ε / (nr + R). In case a, If r << R, then I = (n ε / R) ≈ nI₁. Where, I₁ is the current due to a single cell I₁ = ε/R. Thus, if r is negligible when compared to R the current supplied by the battery is n times that supplied by a single cell.
3. In case of b If r>>R, I = (n ε/n r) ≈ ε / r. It is the current due to a multiple cell. That is, current due to the whole battery is larger than that due to a single cell and hence there is more advantage in connecting several cells. Thus, series connection of cells is advantageous only when the effective internal resistance of the cells is negligibly small compared with R.
4. Both 1 and 2
5. Both 1 and 3
6. Both 2 and 3
7. All 1, 2 and 3

Explanation

In case of b If r>>R, I = (n ε/n r) ≈ ε / r. It is the current due to a single cell. That is, current due to the whole battery is the same as that due to a single cell and hence there is no advantage in connecting several cells. Thus, series connection of cells is advantageous only when the effective internal resistance of the cells is negligibly small compared with R.

65. A battery has an emf of 12 V and connected to a resistor of 3 Ω. The current in the circuit is 3.93A. Calculate power delivered by the battery and power delivered to the resistor

1. P = 46.9 W, P_r = 45.4 W
2. P = 47.1 W, P_r = 46.3 W
3. P = 48.6 W, P_r = 47.2 W
4. P = 49.8 W, P_r = 48.6 W

Explanation

The power delivered by the battery P = Iε = 3.93 × 12 = 47.1 W

The power delivered to the resistor = I² R = 46.3 W

The remaining power P = (47.1 – 46.3) = 0.8 W is delivered to the internal resistance and cannot be used to do useful work. (It is equal to I ² r).

66. Which among the following statement is correct

1. In parallel connection all the positive terminals of the cells are connected to one point and all the negative terminals to a second point. These two points form the positive and negative terminals of the battery. Let n cells be connected in parallel between the points A and B and a resistance R is connected between the points A and B. Let ε be the emf and r the internal resistance of each cell.
2. The total emf is the potential difference between the points A and B, which is equal to ε. The current in the circuit is given by I = [ε / ((r/n) + R)]. Thus, I = n ε/ (r + n R). In case of a If r >> R, I = (n ε/ r) = n I₁. Where I₁ is the current due to a single cell (ε/r) when R is negligible. Thus, the current through the external resistance due to the whole battery is n times the current due to a single cell.
3. In case of b, If r<< R, I = ε / R. The above equation implies that current due to the whole battery is the same as that due to a single cell. Hence it is advantageous to connect cells in parallel when the external resistance is very small compared to the internal resistance of the cells.
4. Both 1 and 2
5. Both 1 and 3
6. Both 2 and 3
7. All 1, 2 and 3

67. When the car engine is started with headlights turned on, they sometimes become dim. This is due to ____

1. Emf of car battery
2. Internal resistance of car battery
3. Voltage point of car battery
4. Super conduction of car batter

Explanation

When the car engine is started with headlights turned on, they sometimes become dim. This is due to the internal resistance of the car battery.

68. Which among the following is used to find current and voltage in complex circuit?

1. Ohms law
2. Pascal law
3. Kirchhoff’s rules
4. Kinetic rules

Explanation

Ohm’s law is useful only for simple circuits. For more complex circuits, Kirchhoff ’s rules can be used to find current and voltage. There are two generalized rules: i) Kirchhoff ’s current rule ii) Kirchhoff ’s voltage rule.

69. Which among the following is not the other name of Kirchhoff’s first rule?

1. Voltage rule
2. Current rule
3. Junction rule
4. None of the above

Explanation

The other name of Kirchhoff’s first rule are Current rule or Junction rule.

70. Which among the following is the other name of Kirchhoff’s Second rule?

1. Slip rule
2. Transmit rule
3. Cupper rule
4. Loop rule

Explanation

The other name of Kirchhoff’s Second rule is Voltage rule or Loop rule.

71. Which among the following statement is correct

1. Kirchhoff’s first rule states that the algebraic sum of the currents at any junction of a circuit is zero. It is a statement of law of conservation of electric charge. The charges that enter a given junction in a circuit must leave that junction since charge cannot build up or disappear at a junction. By convention, current entering the junction is taken as positive and current leaving the junction is taken as negative.
2. Kirchhoff’s Second rule states that in a open circuit the algebraic sum of the products of the current and resistance of each part of the circuit is equal to the total emf included in the circuit. This rule follows from the law of conservation of mass for an isolated system (The energy supplied by the emf sources is equal to the sum of the energy delivered to all resistors).
3. The product of current and resistance is taken as positive when the direction of the current is followed. Suppose if the direction of current is opposite to the direction of the loop, then product of current and voltage across the resistor is negative. The emf is considered positive when proceeding from the negative to the positive terminal of the cell. Kirchhoff voltage rule has to be applied only when all currents in the circuit reach a steady state condition (the current in various branches are constant).
4. Both 1 and 2
5. Both 1 and 3
6. Both 2 and 3
7. All 1, 2 and 3

Explanation

Kirchhoff’s Second rule states that in a closed circuit the algebraic sum of the products of the current and resistance of each part of the circuit is equal to the total emf included in the circuit. This rule follows from the law of conservation of energy for an isolated system (The energy supplied by the emf sources is equal to the sum of the energy delivered to all resistors).

72. Which is an instrument used for detecting and measuring even very small electric currents and is extensively useful to compare the potential difference between various parts of the circuit?

1. Ammeter
2. Voltmeter
3. Galvanometer
4. Dynamometer

Explanation

A galvanometer is an instrument used for detecting and measuring even very small electric currents. It is extensively useful to compare the potential difference between various parts of the circuit.

73. Which among the following statement is correct regarding Wheatstone’s bridge?

1. An important application of Kirchhoff ’s rules is the Wheatstone’s bridge. It is used to compare resistances and in determining the unknown resistance in electrical network. The bridge consists of four resistances P, Q, R and S connected. A galvanometer G is connected between the points B and D. The battery is connected between the points A and C.
2. The current through the galvanometer is I_G and its resistance is G. Applying Kirchhoff ’s current rule to junction B and D respectively. We get 1. I₁ – I_G – I₃ = 0 and 2. I₂ + I_G – I₄ = 0. Applying Kirchhoff ’s voltage rule to loop ABDA, we get 3. I₁ P + I_GG – I₂ R = 0. Applying Kirchhoff ’s voltage rule to loop ABCDA, 4. I₁ P + I₃ Q – I₄ S – I₂ R = 0. When the points B and D are at the same potential, the bridge is said to be balanced.
3. As there is no potential difference between B and D, no current flows through galvanometer (IG = 0). Substituting IG = 0 in equation 1, 2 and 3, we get A. I₁ = I₃, B. I₂ = I₄, and C. I₁P = I₂R. using C in 4 we get D. I₃ Q = I₄ S. Dividing equation D by equation C, we get P/Q = R/S. This is the condition for bridge balance. Only under this condition, galvanometer shows null deflection. Suppose we know the values of two adjacent resistances, the other two resistances can be compared.
4. Both 1 and 2
5. Both 1 and 3
6. Both 2 and 3
7. All 1, 2 and 3

74. What is the value of x when the Wheatstone’s network is balanced?

P = 500 Ω, Q = 800 Ω, R = x + 400, S = 1000 Ω

1. x = 150 Ω
2. x = 225 Ω
3. x = 370 Ω
4. x = 415 Ω

Explanation

P/Q = R/S, when the network is balanced

500/800 = (x+4000)/1000

x + 400 = (5/8) + 1000

x + 400 = 625

x = 625 – 400

x = 225 Ω.

75. Which among the following statement is correct regarding meter bridge?

1. The meter bridge is not another form of Wheatstone’s bridge. It consists of a non-uniform wire of manganin AB of one meter length. This wire is stretched along a metre scale on a wooden board between two copper strips C and D. Between these two copper strips another copper strip E is mounted to enclose two gaps G₁ and G₂.
2. An unknown resistance P is connected in G₁ and a standard resistance Q is connected in G₂. A jockey (conducting wire-contact maker) is connected to the terminal E on the central copper strip through a galvanometer (G) and a high resistance (HR). The exact position of jockey on the wire can be read on the scale. A Lechlanche cell and a key (K) are connected between the ends of the bridge wire.
3. The position of the jockey on the wire is adjusted so that the galvanometer shows zero deflection. Let the position of jockey at the wire be at J. The resistances corresponding to AJ and JB of the bridge wire form the resistances R and S of the Wheatstone’s bridge. Then for the bridge balance = = . where r is the resistance per unit length of wire. = .
4. Both 1 and 2
5. Both 1 and 3
6. Both 2 and 3
7. All 1, 2 and 3

Explanation

The meter bridge is another form of Wheatstone’s bridge. It consists of a uniform wire of manganin AB of one meter length. This wire is stretched along a metre scale on a wooden board between two copper strips C and D. Between these two copper strips another copper strip E is mounted to enclose two gaps G₁ and G₂.

76. In a meter bridge experiment with a standard resistance of 15 Ω in the right gap, the ratio of balancing length is 3:2. Find the value of the other resistance?

1. 13.6 Ω
2. 17.9 Ω
3. 19.1 Ω
4. 22.5 Ω

Explanation

Q = 15 Ω, l₁ : l₂ = 3:2

l₁/ l₂ = 3 / 2

P / Q = l₁ / l₂

P = Q (l₁ / l₂)

P = 15 × (3 / 2) = 22.5 Ω.

77. Which among the following statement is correct regarding potentiometer

1. Potentiometer is used for the accurate measurement of potential differences, current and resistances. It consists of one-meter-long uniform wire of manganin or constantan stretched in parallel rows each of 0.1-meter length, on a wooden board. The two free ends A and B are brought to the same side and fixed to silver strips with binding screws. A meter scale is fixed series to the wire. A jockey is provided for making contact.
2. A steady current is maintained across the wire CD by a battery Bt. The battery, key and the potentiometer wire connected in series form the primary circuit. The positive terminal of a primary cell of emf ε is connected to the point C and negative terminal is connected to the jockey through a galvanometer G and a high resistance HR. This forms the secondary circuit.
3. Let the contact be made at any point J on the wire by jockey. If the potential difference across CJ is equal to the emf of the cell ε, then no current will flow through the galvanometer and it will show zero deflection. CJ is the balancing length l. The potential difference across CJ is equal to Irl where I is the current flowing through the wire and r is the resistance per unit length of the wire. Hence ε = Irl.
4. Both 1 and 2
5. Both 1 and 3
6. Both 2 and 3
7. All 1, 2 and 3

Explanation

Potentiometer is used for the accurate measurement of potential differences, current and resistances. It consists of ten-meter-long uniform wire of manganin or constantan stretched in parallel rows each of 1 meter length, on a wooden board. The two free ends A and B are brought to the same side and fixed to copper strips with binding screws. A meter scale is fixed parallel to the wire. A jockey is provided for making contact.

78. In a meter bridge experiment, the value of resistance in the resistance box connected in the right gap is 10 Ω. The balancing length is l₁ = 55 cm. Find the value of unknown resistance?

1. 11.7 Ω
2. 12.2 Ω
3. 14.8 Ω
4. 16.3 Ω

Explanation

Q = 10 Ω

= =

P = Q × =

P = 550 / 45

P = 12.2 Ω.

79. Which among the following statement is correct regarding Comparison of emf of two cells with a potentiometer

1. To compare the emf of two cells, the circuit connections are made. Potentiometer wire CD is connected to a battery Bt and a key K in series. This is the primary circuit. The end C of the wire is connected to the terminal M of a DPDT (Double Pole Double Throw) switch and the other terminal N is connected to a jockey through a galvanometer G and a high resistance HR.
2. The cells whose emf ε₁ and ε₂ to be compared are connected to the terminals M₁, N₁ and M₂, N₂ of the DPDT switch. The positive terminals of Bt, ε₁ and ε₂ should be connected to the same end C. The DPDT switch is pressed towards M₁, N₁ so that cell ε₁ is included in the secondary circuit and the balancing length l₁ is found by adjusting the jockey for zero deflection.
3. Then the second cell ε₂ is included in the circuit and the balancing length l₂ is determined. Let r be the resistance per unit length of the potentiometer wire and I be the current flowing through the wire. we have ε₁ = Irl₁ and ε₂ = Irl₂. By dividing ε₁ and ε₂, we get (ε₁ / ε₂) = (l₁ / l₂). By including a rheostat (Rh) in the primary circuit, the experiment can be repeated several times by changing the current flowing through it.
4. Both 1 and 2
5. Both 1 and 3
6. Both 2 and 3
7. All 1, 2 and 3

80. Which among the following statement is correct regarding measurement of internal resistance of a cell by potentiometer?

1. To measure the internal resistance of a cell, the circuit connections are made. The end C of the potentiometer wire is connected to the positive terminal of the battery Bt and the negative terminal of the battery is connected to the end D through a key K₁. This forms the primary circuit. The positive terminal of the cell of emf ε whose internal resistance is to be determined is also connected to the end C of the wire.
2. The negative terminal of the cell ε is connected to a jockey through a galvanometer and a high resistance. A resistance box R and key K₂ are connected across the cell ε. With K₂ open, the balancing point J is obtained and the balancing length CJ = l₁ is measured. Since the cell is in open circuit, its emf is ε ∝ l₁ (A).
3. A suitable resistance (say, 10 Ω) is included in the resistance box and key K₁ is closed. Let r be the internal resistance of the cell. The current passing through the cell and the resistance R is given by I = . The potential difference across R is V = . When this potential difference is balanced on the potentiometer wire, let l₂ be the balancing length. Then ∝ l₂ (B). From equation A and B, we get r = ().
4. Both 1 and 2
5. Both 1 and 3
6. Both 2 and 3
7. All 1, 2 and 3

Explanation

A suitable resistance (say, 10 Ω) is included in the resistance box and key K₂ is closed. Let r be the internal resistance of the cell. The current passing through the cell and the resistance R is given by I = . The potential difference across R is V = . When this potential difference is balanced on the potentiometer wire, let l₂ be the balancing length. Then ∝ l₂ (B). From equation A and B, we get r = R ().

81. As current produces thermal energy, thermal energy may also be suitably used to produce an electromotive force. This is known as ______

1. Thermostatic effect
2. Thermoset effect
3. Thermoelectric effect
4. Thermophile effect

Explanation

As current produces thermal energy, thermal energy may also be suitably used to produce an electromotive force. This is known as thermoelectric effect.

82. Which among the following statement is correct

1. If a current I flow through a conductor kept across a potential difference V for a time t, the work done or the electric potential energy spent is W = VIt.
2. In the absence of any other external effect, this energy is spent in heating the conductor. The amount of heat(H) produced is H = VIt. For a resistance R, H = I² Rt. This relation was experimentally verified by newton and is known as newton’s law of heating.
3. It states that the heat developed in an electrical circuit due to the flow of current varies directly as (i) the square of the current (ii) the resistance of the circuit and (iii) the time of flow.
4. Both 1 and 2
5. Both 1 and 3
6. Both 2 and 3
7. All 1, 2 and 3

Explanation

In the absence of any other external effect, this energy is spent in heating the conductor. The amount of heat(H) produced is H = Vit. For a resistance R, H = I² Rt. This relation was experimentally verified by Joule and is known as Joule’s law of heating.

83. Find the heat energy produced in a resistance of 10 Ω when 5 A current flows through it for 5 minutes?

1. H = 75 KJ
2. H = 100 KJ
3. H = 125 KJ
4. H = 140 KJ

Explanation

R = 10 Ω, I = 5 A, t = 5 minutes = 5 × 60 s

H = I² R t = 5² × 10 × 5 × 60 = 25 × 10 × 300

= 25 × 3000

= 75000 J (or) 75 kJ.

84. In Electric heaters, the heating elements are not made of which among the following metal?

1. Nichrome
2. Alloy of nickel
3. Aluminium
4. Chromium

Explanation

Electric iron, electric heater, electric toaster are some of the home appliances that utilize the heating effect of current. In these appliances, the heating elements are made of nichrome, an alloy of nickel and chromium.

85. Which among the following metal has a high specific resistance and can be heated to very high temperatures without oxidation?

1. Nichrome
2. Alloy of nickel
3. Chromium
4. Tungsten

Explanation

Nichrome has a high specific resistance and can be heated to very high temperatures without oxidation.

86. Which are connected in series in a circuit to protect the electric devices from the heat developed by the passage of excessive current?

1. Fuse
2. Peltier
3. Furnace
4. Trip

Explanation

Fuses as shown in Figure 2.31, are connected in series in a circuit to protect the electric devices from the heat developed by the passage of excessive current. It is a short length of a wire made of a low melting point material. It melts and breaks the circuit if current exceeds a certain value.

87. Which alloy is used for fuses when current rating is below 15 A?

1. Copper-lead
2. Lead -tin
3. Silver -copper
4. Copper-tin

Explanation

An alloy of lead – tin is used for fuses when current rating is below 15 A.

88. when current rating is above 15 A, which fuse wires are used?

1. Silver
2. Lead
3. Copper
4. Gold foil

Explanation

When current rating is above 15 A, copper fuse wires are used. The only disadvantage with the above fuses is that once fuse wire is burnt due to excessive current, they need to be replaced.

89. Nowadays which was used in house instead of fuses?

1. Casters
2. Trippers
3. Furnaces
4. Cables

Explanation

Nowadays in houses, circuit breakers (trippers) are also used instead of fuses. Whenever there is an excessive current produced due to faulty wire connection, the circuit breaker switch opens. After repairing the faulty connection, we can close the circuit breaker switch.

90. Which are used to manufacture a large number of technologically important materials such as steel, silicon carbide, quartz, gallium arsenide, etc.?

1. Furnace
2. Lamp
3. Caster
4. Spell

Explanation

Furnaces as shown in Figure 2.33 are used to manufacture a large number of technologically important materials such as steel, silicon carbide, quartz, gallium arsenide, etc.

91. Which furnaces produce temperatures up to 3000°C?

1. Nichrome arc furnace
2. Silver arc furnace
3. Carbon arc furnace
4. Lead arc furnace

Explanation

To produce temperatures up to 1500°C, molybdenum-nichrome wire wound on a silica tube is used. Carbon arc furnaces produce temperatures up to 3000°C.

92. Electric lamp consists of which filament kept inside a glass bulb and heated to incandescence by current?

1. Tin
2. Lead
3. Tungsten
4. Copper

Explanation

Electric lamp consists of a tungsten filament (melting point 33800 C) kept inside a glass bulb and heated to incandescence by current.

93. In incandescent electric lamps how many percentages of electrical energy is converted into light and the rest is wasted as heat?

1. 5%
2. 10%
3. 20%
4. 25%

Explanation

In incandescent electric lamps only about 5% of electrical energy is converted into light and the rest is wasted as heat..

94. Conversion of temperature differences into electrical voltage and vice versa is known as ____

1. Floyd effect
2. Peltier effect
3. Thermoelectric effect
4. Thomson effect

Explanation

Conversion of temperature differences into electrical voltage and vice versa is known as thermoelectric effect. A thermoelectric device generates voltage when there is a temperature difference on each side. If a voltage is applied, it generates a temperature difference.

95. Who discovered that in a closed circuit consisting of two dissimilar metals, when the junctions are maintained at different temperatures an emf (potential difference) is developed?

1. Peltier
2. Thomson
3. Seebeck
4. Kirchhoff

Explanation

Seebeck discovered that in a closed circuit consisting of two dissimilar metals, when the junctions are maintained at different temperatures an emf (potential difference) is developed.

96. Who showed that if two points in a conductor are at different temperatures, the density of electrons at these points will differ and as a result the potential difference is created between these points?

1. Peltier
2. Kirchhoff
3. Thomson
4. Floyd

Explanation

Thomson showed that if two points in a conductor are at different temperatures, the density of electrons at these points will differ and as a result the potential difference is created between these points. Thomson effect is also reversible.

97. In seebeck effect, current that flows due to the emf developed is called ____

1. Thermostatic current
2. Thermoelectric current
3. Thermoscope current
4. Thermopile current

Explanation

In Seebeck effect, current that flows due to the emf developed is called thermoelectric current.

98. In seebeck effect, the two dissimilar metals connected to form two junctions is known as ___

1. Thermoform
2. Thermocouple
3. Thermophile
4. Thermograph

Explanation

In seebeck effect, two dissimilar metals connected to form two junctions is known as thermocouple. If the hot and cold junctions are interchanged, the direction of current also reverses. Hence the effect is reversible. The magnitude of the emf developed in a thermocouple depends on (i) the nature of the metals forming the couple and (ii) the temperature difference between the junctions.

99. Which among the following statement regarding application of seebeck effect is correct

1. Seebeck effect is used in thermoelectric generators (Seebeck generators). These, thermoelectric generators are used in power plants to convert waste heat into electricity.
2. This effect is utilized in automobiles as automotive thermoelectric generators for increasing fuel efficiency.
3. Seebeck effect is used in thermocouples and thermopiles to measure the temperature difference between the two objects.
4. Both 1 and 2
5. Both 1 and 3
6. Both 2 and 3
7. All 1, 2 and 3

100. When an electric current is passed through a circuit of a thermocouple, heat is evolved at one junction and absorbed at the other junction. This is known as ____

1. Thomson effect
2. Peltier effect
3. Floyd effect
4. Kirchhoff effect

Explanation

In 1834, Peltier discovered that when an electric current is passed through a circuit of a thermocouple, heat is evolved at one junction and absorbed at the other junction. This is known as Peltier effect.

101. Which among the following statement is correct regarding Peltier effect: Cu – Fe thermocouple?

1. In the Cu-Fe thermocouple the junctions A and B are maintained at the same temperature. Let a current from a battery flow through the thermocouple. At the junction A, where the current flows from Cu to Fe, heat is absorbed and the junction A becomes cold.
2. At the junction B, where the current flows from Fe to Cu heat is liberated and it becomes hot. When the direction of current is reversed, junction A gets cooled and junction B gets heated. Hence Peltier effect is irreversible.
3. Only 1
4. Only 2
5. Both 1 and 2
6. None

Explanation

At the junction B, where the current flows from Fe to Cu heat is liberated and it becomes hot. When the direction of current is reversed, junction A gets heated and junction B gets cooled. Hence Peltier effect is reversible.

102. Which among the following statement is correct regarding Thomson effect?

1. If current is passed through a copper bar AB which is heated at the middle point C, the point C will be at higher potential. This indicates that the heat is absorbed along AC and evolved along CB of the conductor. Thus, heat is transferred due to the current flow in the direction of the current. It is called positive Thomson effect.
2. When the copper bar is replaced by an iron bar, heat is evolved along CA and absorbed along BC. Thus, heat is transferred due to the current flow in the direction opposite to the direction of current. It is called negative Thomson effect.
3. Only 1
4. Only 2
5. Both 1 and 2
6. None

103. In which among the following metal positive Thomson effect is not observed?

1. Silver
2. Zinc
3. Iron
4. Copper

Explanation

positive Thomson effect are observed in metal like silver, zinc, and copper

104. In which among the following metal negative Thomson effect is not observed?

1. Platinum
2. Cobalt
3. Mercury
4. Cadmium

Explanation

Negative Thomson effect are observed in metal like platinum, nickel, cobalt, and mercury. Cadmium metal is used in Positive Thomson effect.

105. During lightning charges flow between the clouds and ____.

a) Ground

b) Atmosphere

c) Ions

d) Charged particles.

Explanation

Electric current is not only produced by batteries. In nature, lightning bolt produces enormous electric current in a short time. During lightning, very high potential difference is created between the clouds and ground and hence charges flow between the clouds and ground.

106. Choose the correct statements.

i) If there is no electric field, the electrons move in random directions.

ii) The number of electrons travelling in any direction will be equal to the number of electrons travelling in the opposite direction.

iii) No net flow of electrons in any direction and no current if the electric field is not present.

a) i only

b) ii only

c) iii only

d) All the above

Explanation

If there is no electric field, the electrons move in random directions, and hence their velocities are also randomly oriented. On an average, the number of electrons travelling in any direction will be equal to the number of electrons travelling in the opposite direction. As a result, there is no net flow of electrons in any direction and hence there will not be any current.

107. Choose the incorrect statements.

a) Any material is made up of neutral atoms with equal number of electrons and protons.

b) Outermost electrons leaving the atoms become free electrons and are responsible for electric current.

c) Atoms after losing their outer most electrons will have more negative charges.

d) The positive ions in the atom will not give rise to current.

Explanation

Any material is made up of neutral atoms with equal number of electrons and protons. If the outermost electrons leave the atoms, they become free electrons and are responsible for electric current. The atoms after losing their outer most electrons will have more positive charges and hence are called positive ions. These ions will not move freely within the material like the free electrons. Hence the positive ions will not give rise to current.

108. What is the direction of electric field?

a) Conventional current density direction

b) Potential rise

c) Direction of the positive ions.

d) Opposite to the current density

Explanation

In general, the current density is a vector quantity. But conventionally, we take the direction of (conventional) current density as the direction of electric field.

109. Which of the following statements are not true regarding Ohm’s law?

a) Materials do not follow Ohm’s law are called as non-ohmic.

b) Non-ohmic materials have more complex relationships between voltage and current.

c) Non-ohmic materials have a constant resistance.

d) A plot of I versus V for a non-ohmic material is non-linear.

Explanation

Materials or devices that do not follow Ohm’s law are said to be non-ohmic. These materials have more complex relationships between voltage and current. A plot of I versus V for a non-ohmic material is non-linear and they do not have a constant resistance.

110. Identify the incorrect Match.

Materials Resistivity at 20°C

A. Fused Quartz i) 10¹⁶

B. Silicon ii) 0.46

C. Iron iii) 10 x 10^-8

D. Pure water iv) 2.5 x 10⁵

a) i only

b) ii only

c) iii only

d) iv only

Explanation

111. Identify the Incorrect match

A. Water i) 200 Ω

B. Wet human skin ii) 1000 Ω

C. Dry skin iii) 5 Ω

a) i only

b) ii only

c) iii only

d) None of the above

Explanation

The human body contains a large amount of water which has low resistance of around 200 Ω and the dry skin has high resistance of around 500 k Ω. But when the skin is wet, the resistance is reduced to around1000 Ω. This is the reason why repairing the electrical connection with the wet skin is always dangerous.

112. What is the value of supply voltage if more than one resistors are connected in a circuit?

a) Sum of the voltages across each resistor.

b) Square value of the resistances

c) Voltage across the high value resistor.

d) Less than the value of low resistance value.

Explanation

According to Ohm’s law, if same current pass through different resistors of different values, then the potential difference across each resistor must be different. If V1, V2 and V3 be the potential differences (voltage) across each of the resistors R1, R2 and R3 respectively, But the supply voltage V must be equal to the sum of voltages(potential differences) across each resistor.

113. The value of the total resistance of a parallel connection is____

a) Sum of all resistance value

b) Inverse of the highest resistance value.

c) Less than the individual resistance.

d) Smallest value of resistance

Explanation

The value of equivalent resistance in parallel connection will be lesser than each individual resistance.

114. Why the household appliances are always connected parallel?

a) Even if one is switched off, the other devices could function properly.

b) High equivalent resistance value.

c) Potential difference is very low.

d) Charge flow is constant

Explanation

House hold appliances are always connected in parallel so that even if one is switched off, the other devices could function properly.

115. Which of the following statement is not correct regarding the carbon resistors?

a) Ceramic core with a thin layer of crystalline carbon.

b) Inexpensive, stable and compact in size

c) Complex design

d) Colour rings indicates the value of the resistance

Explanation

Carbon resistors consists of a ceramic core, on which a thin layer of crystalline carbon is deposited. These resistors are inexpensive, stable and compact in size. Colour rings are used to indicate the value of the resistance according to the rules.

116. Which of the ring indicated the decimal multiplier value of the three colored resistance?

a) 1^st

b) 3^rd

c) 2^nd

d) 4^th

Explanation

Three coloured rings are used to indicate the values of a resistor: the first two rings are significant figures of resistances, the third ring indicates the decimal multiplier after them. The fourth colour, silver or gold shows the tolerance of the resistor at 10% or 5%.

117. What is the value of the tolerance if the fourth ring is not present in a resistor?

a) 20%

b) 15%

c) 100%

d) 5%

Explanation

If there is no fourth ring in the carbon resistor, the tolerance is 20%.

118. Choose the correct statements.

i) While reading the colour code, hold the resistor with colour bands to your right.

ii) Resistors never start with a metallic band on the left.

a) i only

b) ii only

c) Both i and ii

d) Neither i nor ii

Explanation

While reading the colour code, hold the resistor with colour bands to your left. Resistors never start with a metallic band on the left.

119. What is the value of resistivity as the temperature approaches absolute zero?

a) Infinity

b) Unity

c) Zero

d) Finite value

Explanation

Though, the resistivity of conductors like metals varies linearly for wide range of temperatures, there also exists a non-linear region at very low temperatures. The resistivity approaches some finite value as the temperature approaches absolute zero.

120. What is the value of the temperature coefficient of resisitivity of iron?

a) 5.0 x 10^-3

b) 3.9 x 10^-3

c) -0.5 x 10^-3

d) -75 x 10^-3

Explanation

121. Which of these is used for complex circuits?

a) Ohm’s law

b) Coulomb’s law

c) Kirchhoff’s rule

d) Faraday’s law

Explanation

Ohm’s law is useful only for simple circuits. For more complex circuits, Kirchhoff ’s rules can be used to find current and voltage.

122. What is the temperature value of the superconductors?

a) Critical temperature

b) Equivalent temperature

c) Transition temperature

d) Both a and c

Explanation

The resistance of certain materials become zero below certain temperature Tc. This temperature is known as critical temperature or transition temperature. The materials which exhibit this property are known as superconductors.

123. In which of these material Kammerlingh observed the superconductor phenomenon?

a) Mercury

b) Gold

c) Tungsten

d) Diamond

Explanation

The superconductor phenomenon was first observed by Kammerlingh Onnes in 1911. He found that mercury exhibits superconductor behaviour at 4.2 K. Since R = 0, current once induced in a superconductor persists without any potential difference.

124. Which of these metals are used for end resistance?

a) Copper strips

b) Lead

c) Iron

d) Cadmium

Explanation

The bridge wire is soldered at the ends of the copper strips. Due to imperfect contact, some resistance might be introduced at the contact. These are called end resistances.

125. Which of the following is not measured with a potentiometer?

a) Potential difference

b) Conductivity

c) Current

d) Resistance

Explanation

Potentiometer is used for the accurate measurement of potential differences, current and resistances.

126. The potential difference or the emf of a cell is directly proportional to the ___.

a) Number of positive charges

b) Total number of resistors

c) Balancing length

d) Permiability

Explanation

The potential difference is equal to Irl where I is the current flowing through the wire and r is the resistance per unit length of the wire.Hence ε = Irl Since I and r are constants, ε ∝l. The emf of the cell is directly proportional to the balancing length.

127. Which of these is used to vary the current flow in the circuit?

a) Rheostat

b) Galvanometer

c) Ammeter

d) Capacitance

Explanation

By including a rheostat (Rh) in the primary circuit, the experiment can be repeated several times by changing the current flowing through it.

128. As per the Joule’s law the heat developed in a electrical circuit is varied with ,

i) Square of the current

ii) Resistance of the circuit

iii) Time of flow

a) i only

b) ii only

c) iii only

d) All the above

Explanation

Joule’s law of heating. It states that the heat developed in an electrical circuit due to the flow of current varies directly as the square of the current, the resistance of the circuit and the time of flow.

129. Which of these device does not use the heating effect of the current?

a) Eledctric arc

b) Discharge lamps

c) Microwave

d) Electric welding

Explanation

Electric discharge lamps, electric welding and electric arc also utilize the heating effect of current.

130. Which of these value is dependent on the magnitude of the emf in a thermocouple?

a) Nature of the metals

b) Potential difference between the metals.

c) Temperature difference between the junctions.

d) Both a and c

Explanation

The magnitude of the emf developed in a thermocouple depends on (i) the nature of the metals forming the couple and (ii) the temperature difference between the junctions.

12th Science Lesson 8 Questions in English

8] Magnetism and Magnetic effect of electric current

1. Historically the word ‘magnetism’ was derived from which ore?

1. Copper ore
2. Iron ore
3. Silver ore
4. Magnesium ore

Explanation

Magnetism exists everywhere from tiny particles like electrons to the entire universe. Historically the word ‘magnetism’ was derived from iron ore magnetite (Fe3 O4 ). In olden days, magnets were used as magnetic compass for navigation, magnetic therapy for treatment and also used in magic shows.

2. In 1820, Who observed the deflection of magnetic compass needle kept near a current carrying wire?

1. J.C. Maxwell
2. Michael Faraday
3. H.C. Oersted
4. William Gilbert

Explanation

Earlier, both electricity and magnetism were thought to be two independent branches in physics. In 1820, H.C. Oersted observed the deflection of magnetic compass needle kept near a current carrying wire. This unified the two different branches, electricity and magnetism as a single subject ‘electromagnetism’ in physics.

3. Magnetic sensing in eyes – for Zebra finch bird, due to which protein present in retina?

1. Elastin cry 4
2. Cryptochrome cry 4
3. Collagen cry 4
4. Scleroprotein cry 4

Explanation

Magnetic sensing in eyes – for Zebra finch bird, due to protein cryptochromes Cry4 present in retina; the bird uses Earth’s magnetic field for navigation.

4. Who in 1600 proposed that Earth itself behaves like a gigantic powerful bar magnet?

1. Stephen Gray
2. Alessandro Volta
3. Benjamin Franklin
4. William Gilbert

Explanation

William Gilbert in 1600 proposed that Earth itself behaves like a gigantic powerful bar magnet. But this theory is not successful because the temperature inside the Earth is very high and so it will not be possible for a magnet to retain its magnetism.

5. The branch of physics which deals with the Earth’s magnetic field is called ____

1. Cover magnetism
2. Terrestrial magnetism
3. Slide magnetism
4. Neo-magnetism

Explanation

The north pole of magnetic compass needle is attracted towards the magnetic south pole of the Earth which is near the geographic north pole. Similarly, the south pole of magnetic compass needle is attracted towards the magnetic north-pole of the Earth. The branch of physics which deals with the Earth’s magnetic field is called Geomagnetism or Terrestrial magnetism.

6. Which among the following quantity is not required to specify the magnetic field of the earth on its surface?

1. Magnetic subjunctive
2. Magnetic declination
3. Magnetic dip
4. The horizontal component of the Earth’s magnetic field

Explanation

There are three quantities required to specify the magnetic field of the Earth on its surface, which are often called as the elements of the Earth’s magnetic field. They are (a) magnetic declination (D) (b) magnetic dip or inclination (I) (c) the horizontal component of the Earth’s magnetic field (B_H).

7. Day and night occur because Earth spins about an axis called ____

1. Altitude axis
2. Geographic axis
3. Analog axis
4. Orbital axis

Explanation

Day and night occur because Earth spins about an axis called geographic axis.

8. A vertical plane passing through the geographic axis is called _____

1. Geographic stratosphere
2. Geographic meridian
3. Geographic equator
4. Geographic core

Explanation

A vertical plane passing through the geographic axis is called geographic meridian and a great circle perpendicular to Earth’s geographic axis is called geographic equator.

9. Which among the following statement is correct

1. The straight line which connects magnetic poles of Earth is known as needle axis. A vertical plane passing through needle axis is called magnetic meridian and a great circle perpendicular to Earth’s needle axis is called magnetic equator.
2. When a magnetic needle is freely suspended, the alignment of the magnet does not exactly lie along the geographic meridian.
3. Only 1
4. Only 2
5. Both 1 and 2
6. None

Explanation

The straight line which connects magnetic poles of Earth is known as magnetic axis. A vertical plane passing through magnetic axis is called magnetic meridian and a great circle perpendicular to Earth’s magnetic axis is called magnetic equator.

10. The angle between magnetic meridian at a point and geographical meridian is called _____

1. Magnetic declination
2. Magnetic inclination
3. Dip
4. All the above

Explanation

The angle between magnetic meridian at a point and geographical meridian is called the declination or magnetic declination (D). At higher latitudes, the declination is greater whereas near the equator, the declination is smaller. In India, declination angle is very small and for Chennai, magnetic declination angle is –1^o 16ʹ (which is negative (west)).

11. The angle subtended by the Earth’s total magnetic field ρ B with the horizontal direction in the magnetic meridian is called _____

1. Scapes diagonal
2. Dip
3. Magnetic projection
4. All the above

Explanation

The angle subtended by the Earth’s total magnetic field ρ B with the horizontal direction in the magnetic meridian is called dip or magnetic inclination (I) at that point. For Chennai, inclination angle is 14^o 28’.

12. The horizontal component of Earth’s magnetic field, denoted by ____

1. B_T
2. B_M
3. B_C
4. B_H

Explanation

The component of Earth’s magnetic field along the horizontal direction in the magnetic meridian is called horizontal component of Earth’s magnetic field, denoted by B_H.

13. Which among the following statement is correct

1. Let B_E be the net Earth’s magnetic field at any point on the surface of the Earth. B_E can be resolved into two perpendicular components. Horizontal component B_H = B_E cos I. Vertical component B_V = B_E sin I. By dividing both vertical and horizontal, tan I = .
2. At magnetic equator, Earth’s magnetic field is parallel to the surface of the Earth (i.e., horizontal) which implies that the needle of magnetic compass rests horizontally at an angle of dip, I = 180^o., B_H = B_E., B_V = 0. This implies that the horizontal component is minimum and vertical component is maximum at the equator.
3. At magnetic poles, Earth’s magnetic field is perpendicular to the surface of the Earth (i.e., vertical) which implies that the needle of magnetic compass rests vertically at an angle of dip, I = 90^o. Hence, B_H = 0., B_V = B_E. This implies that the vertical component is maximum at poles and horizontal component is zero at poles.
4. Both 1 and 2
5. Both 1 and 3
6. Both 2 and 3
7. All 1, 2 and 3

Explanation

At magnetic equator, Earth’s magnetic field is parallel to the surface of the Earth (i.e., horizontal) which implies that the needle of magnetic compass rests horizontally at an angle of dip, I = 0^o., B_H = B_E., B_V = 0. This implies that the horizontal component is maximum and vertical component is zero at the equator.

14. The horizontal component and vertical component of Earth’s magnetic field at a place are 0.15 G and 0.26 G respectively. Calculate the angle of dip and resultant magnetic field. (G-gauss, cgs unit for magnetic field 1G = 10^–4 T)?

1. 0.1 G
2. 0.2 G
3. 0.3 G
4. 0.5 G

Explanation

B_H = 0.15 G and B_V = 0.26 G

tan I = 0.26 / 0.15. ⇒ I = tan^-1 (1.732) = 60⁰.

The resultant magnetic field of the Earth is

B = B²_H + B²_H = 0.3 G.

15. Which is defined as the product of its pole strength and magnetic length?

1. Magnetic field
2. Magnetic flux
3. Magnetic current
4. Magnetic dipole movement

Explanation

The magnetic dipole moment is defined as the product of its pole strength and magnetic length.

16. Which among the following statement is correct

1. Consider a bar magnet. Let q_m be the pole strength of the magnetic pole and let l be the distance between the geometrical centre of bar magnet O and one end of the pole. The magnetic dipole moment is defined as the product of its pole strength and magnetic length. It is a vector quantity, denoted by p_m.
2. P_m = q_m + d. where d is the vector drawn from north pole to south pole and its magnitude ρ |d| = 2l. The SI unit of magnetic moment is Am³. The direction of magnetic moment is from south pole to north pole.
3. Only 1
4. Only 2
5. Both 1 and 2
6. None

Explanation

P_m = q_m d. where ρ d is the vector drawn from south pole to north pole and its magnitude ρ |d| = 2l. The SI unit of magnetic moment is Am². The direction of magnetic moment is from south pole to north pole.

17. What was the other name of northern lights?

1. Aurora australis
2. Aurora pinnacle
3. Aurora borealis
4. Aurora trop

Explanation

People living at high latitude regions (near Arctic or Antarctic) might experience dazzling-coloured natural lights across the night sky. This ethereal display on the sky is known as aurora borealis (northern lights) or aurora australis (southern lights).

18. Northern lights and Southern lights are often called as _____

1. Tropical lights
2. Polar lights
3. Equator lights
4. Pacific lights

Explanation

Northern lights and Southern lights are often called as polar lights. The lights are seen above the magnetic poles of the northern and southern hemispheres.

19. Which among the following statement is incorrect

1. Polar lights are called as “Aurora borealis” in the north and “Aurora australis” in the south. This occurs as a result of interaction between the gaseous particles in the Earth’s atmosphere with highly charged particles released from the Sun’s atmosphere through solar wind.
2. These particles emit light due to collision and variations in colour are due to the type of the gas particles that take part in the collisions. A pale yellowish – green colour is produced when the ionized carbon takes part in the collision and a blue or purplish – red aurora is produced due to ionized hydrogen molecules.
3. Only 1
4. Only 2
5. Both 1 and 2
6. None

Explanation

These particles emit light due to collision and variations in colour are due to the type of the gas particles that take part in the collisions. A pale yellowish – green colour is produced when the ionized oxygen takes part in the collision and a blue or purplish – red aurora is produced due to ionized nitrogen molecules.

20. Which is defined as a force experienced by the bar magnet of unit pole strength?

1. Magnetic dipole
2. Magnetic flux
3. Magnetic current
4. Magnetic field

Explanation

Magnetic field is the region or space around every magnet within which its influence will be felt by keeping another magnet in that region. The magnetic field B at a point is defined as a force experienced by the bar magnet of unit pole strength.

B = (1 / q_m) F

21. What is the unit of magnetic field?

1. N A m
2. N A^-1 m^-1
3. N A^-1 m^-2
4. N A^-2 m^-2

Explanation

The unit of magnetic field is N A^-1 m^-1

22. If the magnet is in the form of rectangular shape or cylindrical shape, then it is known ___

1. Coal magnet
2. Pole magnet
3. Bar magnet
4. Polish magnet

Explanation

If the magnet is in the form of rectangular shape or cylindrical shape, then it is known as bar magnet.

23. Which among the following is the natural magnet?

1. Iron
2. Cobalt
3. Nickle
4. All the above

Explanation

Magnets are classified into natural magnets and artificial magnets. For example, iron, cobalt, nickel, etc. are natural magnets. Strengths of natural magnets are very weak and the shapes of the magnet are irregular. Artificial magnets are made in order to have desired shape and strength.

24. Which among the following statement is correct regarding properties of magnet

1. A freely suspended bar magnet will always point along the east-west direction. A magnet attracts or repels another magnet or magnetic substances towards itself. The attractive or repulsive force is maximum near the end of the bar magnet. When a bar magnet is dipped into iron filling, they repel to the ends of the magnet.
2. When a magnet is broken into pieces, each piece behaves like a magnet with poles at its ends. Two poles of a magnet have pole strength equal to one another.
3. The length of the bar magnet is called geometrical length and the length between two magnetic poles in a bar magnet is called magnetic length. Magnetic length is always slightly smaller than geometrical length. The ratio of magnetic length and geometrical length is 5 / 6.
4. Both 1 and 2
5. Both 1 and 3
6. Both 2 and 3
7. All 1, 2 and 3

Explanation

A freely suspended bar magnet will always point along the north-south direction. A magnet attracts or repels another magnet or magnetic substances towards itself. The attractive or repulsive force is maximum near the end of the bar magnet. When a bar magnet is dipped into iron filling, they cling to the ends of the magnet.

25. Compute the magnetic length of a uniform bar magnet if the geometrical length of the magnet is 12 cm.

1. 5 cm
2. 10 cm
3. 12 cm
4. 24 cm

Explanation

Magnetic length = (5/6) × geometrical length

= (5/6) × 12

= 10 cm.

26. Which among the following statement is correct regarding magnetic lines

1. Magnetic field lines are continuous closed curves. The direction of magnetic field lines is from North pole to South pole outside the magnet and from South pole to North pole inside the magnet.
2. The direction of magnetic field at any point on the curve is known by drawing tangent to the magnetic field lines at that point. Magnetic field lines never intersect each other. Otherwise, the magnetic compass needle would point towards two different directions, which is not possible.
3. The degree of closeness of the field lines determines the relative strength of the magnetic field. The magnetic field is weak where magnetic field lines crowd and strong where magnetic field lines are well separated.
4. Both 1 and 2
5. Both 1 and 3
6. Both 2 and 3
7. All 1, 2 and 3

Explanation

The degree of closeness of the field lines determines the relative strength of the magnetic field. The magnetic field is strong where magnetic field lines crowd and weak where magnetic field lines are well separated.

27. The number of magnetic field lines crossing any area normally is defined as ______

1. Magnetic field
2. Magnetic flux
3. Magnetic rae
4. Magnetic plot

Explanation

The number of magnetic field lines crossing any area normally is defined as magnetic flux Φ_B through the area. Mathematically, the magnetic flux through a surface of area ρ A in a uniform magnetic field B is defined as Φ_B = B.A = BA cos θ = B A. where θ is the angle between B and A. When B is normal to the surface i.e., θ = 0⁰, Φ_B = BA. When B is parallel to the surface i.e., θ = 90⁰, Φ_B = 0

28. The SI unit for magnetic flux is _____

1. Newton
2. Joule
3. Pascal
4. Weber

Explanation

Magnetic flux is a scalar quantity. The SI unit for magnetic flux is weber, which is denoted by symbol Wb. Dimensional formula for magnetic flux is [ML² T² A^-1].

29. The CGS unit of magnetic flux is _____

1. Pascal
2. Maxwell
3. Faraday
4. Tesla

Explanation

The CGS unit of magnetic flux is maxwell. 1 weber = 10⁸ maxwell.

30. Which is defined as the number of magnetic field lines crossing per unit area kept normal to the direction of lines of force?

1. Magnetic field density
2. Magnetic field pulse
3. Magnetic field thermo
4. Magnetic field flip

Explanation

The magnetic flux density is defined as the number of magnetic field lines crossing per unit area kept normal to the direction of lines of force.

31. What is the unit of Magnetic flux density?

1. Tesla
2. Maxwell
3. Newton
4. Pascal

Explanation

The unit of magnetic flux density is Tesla (T) or Wb m^-2.

32. Which among the following statement is correct

1. Magnetic field is said to be uniform if it has same magnitude and direction at all the points in a given region. Example, locally Earth’s magnetic field is uniform. The magnetic field of Earth has same value over the entire area of your school!
2. Magnetic field is said to be non-uniform if the magnitude or direction or both vary at different points in a region. Example: magnetic field of a bar magnet.
3. Only 1
4. Only 2
5. Both 1 and 2
6. None

33. Which among the following statement is correct regarding coulomb’s inverse square law of magnetism.

1. Consider two bar magnets A and B. When the north pole of magnet A and the north pole of magnet B or the south pole of magnet A and the south pole of magnet B are brought closer, they repel each other. On the other hand, when the north pole of magnet A and the south pole of magnet B or the south pole of magnet A and the north pole of magnet B are brought closer, their poles attract each other.
2. This looks similar to Coulomb’s law for static charges studied (opposite charges attract and like charges repel each other). So analogous to Coulomb’s law in electrostatics, we can state Coulomb’s law for magnetism.
3. The force of attraction or repulsion between two magnetic poles is directly proportional to the product of their pole strengths and inversely proportional to the square of the distance between them. Mathematically, we can write in magnitude F = k .
4. Both 1 and 2
5. Both 1 and 3
6. Both 2 and 3
7. All 1, 2 and 3

34. The repulsive force between two magnetic poles in air is 9 × 10^–3 N. If the two poles are equal in strength and are separated by a distance of 10 cm, calculate the pole strength of each pole?

1. 10 NT^-1
2. 20 NT^-1
3. 30 NT^-1
4. 40 NT^-1

Explanation

F = k .

Given: F = 9 × 10^–3 N, r = 10 cm = 10 × 10^–2

Since q_mA = q_mB = q_m, we have

9 × 10^-3 = 10^-7 × (q_m² / (10 × 10^-2))

q_m= 30 NT^-1.

35. Which is defined as the ability of the materials to retain the magnetism in them even after the magnetising field disappears?

1. Coercivity
2. Remanence
3. Hysteresis
4. All the above

Explanation

Remanence is defined as the ability of the materials to retain the magnetism in them even after the magnetising field disappears.

36. Which among the following statement is correct regarding hysteresis?

1. When a ferromagnetic material is kept in a magnetising field, the material gets magnetised by induction. An important characteristic of ferromagnetic material is that the variation of magnetic induction B with magnetising field H is not linear. It means that the ratio B / H = µ is not a constant.
2. A ferromagnetic material (example, Iron) is magnetised rapidly by a magnetising field H. The magnetic induction B of the material increases from point A with the magnitude of the magnetising field and then attains a critical level. This response of the material is depicted by the path AC. Critical magnetization is defined as the maximum point up to which the material can be magnetised by applying the magnetising field.
3. If the magnetising field is now reduced, the magnetic induction also decreases but does not retrace the original path CA. It takes different path CD. When the magnetising field is zero, the magnetic induction is not zero and it has positive value. This implies that some magnetism is left in the specimen even when H = 0. The residual magnetism AD present in the specimen is called remanence or retentivity.
4. Both 1 and 2
5. Both 1 and 3
6. Both 2 and 3
7. All 1, 2 and 3

Explanation

A ferromagnetic material (example, Iron) is magnetised slowly by a magnetising field H. The magnetic induction B of the material increases from point A with the magnitude of the magnetising field and then attains a saturation level. This response of the material is depicted by the path AC. Saturation magnetization is defined as the maximum point up to which the material can be magnetised by applying the magnetising field.

37. The magnitude of the reverse magnetising field for which the residual magnetism of the material vanishes is called _____

1. Retentivity
2. Saturation
3. Coercivity
4. All the above

Explanation

In order to demagnetise the material, the magnetising field is gradually increased in the reverse direction. The magnitude of the reverse magnetising field for which the residual magnetism of the material vanishes is called its coercivity.

38. The phenomenon of lagging of magnetic induction behind the magnetising field is called ___

1. Hysteresis
2. Saturation
3. Coherent
4. None of the above

Explanation

In the entire cycle, the magnetic induction B lags behind the magnetising field H. This phenomenon of lagging of magnetic induction behind the magnetising field is called hysteresis. Hysteresis means ‘lagging behind’. This closed curve ACDEFGKC is called hysteresis loop and it corresponds to one cycle of magnetisation.

39. Which among the following statement is incorrect

1. During the magnetisation of the specimen through a cycle, there is loss of energy in the form of heat. This loss is attributed to the rotation and orientation of molecular magnets in various directions. It is found that the energy lost (or dissipated) per unit volume of the material when it is carried through one cycle of magnetisation is equal to the area of the hysteresis loop.
2. Based on the shape and size of the hysteresis loop, ferromagnetic materials are classified as soft magnetic materials with smaller area and hard magnetic materials with larger area. In Soft ferromagnetic materials area of the loop is small, low retentivity, less hysteresis loss. In Hard ferromagnetic materials area of loop is large, high retentivity and more hysteresis loss.
3. Only 1
4. Only 2
5. Both 1 and 2
6. None

40. Which among the following is not the Soft ferromagnetic material?

1. Mumetal
2. Stalloy
3. Alnico
4. None of the above

Explanation

Soft iron, Mumetal, Stalloy etc are soft ferromagnetic materials and Carbon steel, Alnico, Lodestone etc. are Hard ferromagnetic materials.

41. Which among the following information is not given by hysteresis loop?

1. Retentivity
2. Permeability
3. Coercivity
4. Palatability

Explanation

The significance of hysteresis loop is that it provides information such as retentivity, coercivity, permeability, susceptibility and energy loss during one cycle of magnetisation for each ferromagnetic material. Therefore, the study of hysteresis loop will help us in selecting proper and suitable material for a given purpose.

42. The materials with high retentivity, high coercivity and low permeability are suitable for making which magnet?

1. Core of transformer
2. Permanent magnet
3. Electromagnets
4. Both permanent and electro magnet.

Explanation

The materials with high retentivity, high coercivity and low permeability are suitable for making permanent magnets.

43. Which among the following is not the example of electromagnets?

1. Soft iron
2. Mumetal
3. Carbon steel
4. None of the above

Explanation

The materials with high initial permeability, low retentivity, low coercivity and thin hysteresis loop with smaller area are preferred to make electromagnets. Examples: Soft iron and Mumetal (Nickel Iron alloy).

44. Which among the following is the core of the transformer?

1. Soft iron
2. Carbon steel
3. Alnico
4. All the above

Explanation

The materials with high initial permeability, large magnetic induction and thin hysteresis loop with smaller area are needed to design transformer cores. Examples: Soft iron.

45. Which among the following statement is correct regarding Oersted experiment

1. In 1820 Hans Christian Oersted, while preparing for his lecture in physics, noticed that electric current passing through a wire deflects the nearby magnetic needle in the compass. By proper investigation, he observed that the deflection of magnetic needle is due to the change in magnetic field produced around current carrying conductor.
2. When the direction of current is reversed, the magnetic needle is deflected in the opposite direction. This lead to the development of the theory ‘electromagnetism’ which unifies two branches in physics namely, electricity and magnetism.
3. Only 1
4. Only 2
5. Both 1 and 2
6. None

46. Which among the following statement is correct regarding Current carrying straight conductor?

1. Suppose we keep a magnetic compass near a current-carrying straight conductor, then the needle of the magnetic compass experiences a torque and deflects to align in the direction of the magnetic field at that point.
2. Tracing out the direction shown by magnetic needle, we can draw the magnetic field lines at a distance. For a straight current-carrying conductor, the nature of magnetic field is like concentric circles having their common centre on the axis of the conductor.
3. The direction of circular magnetic field lines will be always clockwise independent on the direction of current in the conductor. If the strength (or magnitude) of the current is increased then the density of the magnetic field will decrease. The strength of the magnetic field (B) decreases as the distance (r) from the conductor also decreases.
4. Both 1 and 2
5. Both 1 and 3
6. Both 2 and 3
7. All 1, 2 and 3

Explanation

The direction of circular magnetic field lines will be clockwise or anticlockwise depending on the direction of current in the conductor. If the strength (or magnitude) of the current is increased then the density of the magnetic field will also increase. The strength of the magnetic field (B) decreases as the distance (r) from the conductor increases.

47. Which among the following is not the example of permanent magnets?

1. Carbon steel
2. Alnico
3. Soft iron
4. None of the above

Explanation

The materials with high retentivity, high coercivity and low permeability are suitable for making permanent magnets. Examples: Carbon steel and Alnico.

48. Which among the following statement is correct regarding Circular coil carrying current?

1. Suppose we keep a magnetic compass near a current carrying circular conductor, then the needle of the magnetic compass experiences a torque and deflects to align in the direction of the magnetic field at that point.
2. We can notice that at the points A and B in the vicinity of the coil, the magnetic field lines are circular. The magnetic field lines are nearly perpendicular to other near the centre of the loop, indicating that the field present near the centre of the coil is almost non-uniform.
3. The strength of the magnetic field is increased if either the current in the coil or the number of turns or both are increased. The polarity (north pole or south pole) depends on the direction of current in the loop.
4. Both 1 and 2
5. Both 1 and 3
6. Both 2 and 3
7. All 1, 2 and 3

Explanation

We can notice that at the points A and B in the vicinity of the coil, the magnetic field lines are circular. The magnetic field lines are nearly parallel to each other near the centre of the loop, indicating that the field present near the centre of the coil is almost uniform.

49. Assume that we hold the current carrying conductor in our right hand such that the thumb points in the direction of current flow, then the fingers encircling the conductor point in the direction of ______

1. Magnetic flux
2. Magnetic field
3. Magnetic dipole
4. All the above

Explanation

The right-hand rule is used to find the direction of magnetic field when the direction of current in a conductor is known. Assume that we hold the current carrying conductor in our right hand such that the thumb points in the direction of current flow, then the fingers encircling the conductor point in the direction of the magnetic field lines produced.

50. Whose right hand cork screw rule can also be used to find the direction of the magnetic field around the current-carrying conductor?

1. Newton
2. Weber
3. Maxwell
4. Pascal

Explanation

Maxwell’s right hand cork screw rule can also be used to find the direction of the magnetic field around the current-carrying conductor. If we rotate a right-handed screw using a screw driver, then the direction of current is same as the direction in which screw advances and the direction of rotation of the screw gives the direction of the magnetic field.

51. Soon after Oersted’s discovery, who in 1819 did quantitative experiments on the force experienced by a magnet kept near current carrying wire and arrived at a mathematical expression that gives the magnetic field?

1. Jean-Baptiste Biot and Felix Savart
2. Michael Faraday and Andre Marie Ampere
3. Hendrick Lorentz and Felix Savart
4. James Maxwell and Hendrick Lorentz

Explanation

Soon after Oersted’s discovery, both Jean-Baptiste Biot and Felix Savart in 1819 did quantitative experiments on the force experienced by a magnet kept near current carrying wire and arrived at a mathematical expression that gives the magnetic field at some point in space in terms of the current that produces the magnetic field. This is true for any shape of the conductor.

52. Which among the following is incorrect: Biot and Savart experimentally observed that the magnitude of magnetic field dB at a point P at a distance r from the small elemental length taken on a conductor carrying current varies

1. Directly as the strength of the current I
2. Directly as the magnitude of the length element dl
3. Directly as the sine of the angle θ between dl and r
4. Directly as the square of the distance r between the point P and length element dl.

Explanation

Biot and Savart experimentally observed that the magnitude of magnetic field dB ρ at a point P at a distance r from the small elemental length taken on a conductor carrying current varies (i) directly as the strength of the current I (ii) directly as the magnitude of the length element dl (iii) directly as the sine of the angle θ between dl and r and (iv) inversely as the square of the distance r between the point P and length element dl. This is expressed as dB = K sinθ.

53. What is the value of K in SI units in dB = K sinθ.?

1. µ₀ / π
2. µ₀ / 2π
3. µ₀ / 4π
4. µ₀ / 8π

Explanation

K = . In vector notation, dB = K sinθ. Here vector dB is perpendicular to both Idl (pointing the direction of current flow) and the unit vector r directed from dl toward point P. The equation is used to compute the magnetic field only due to a small elemental length dl of the conductor. The net magnetic field at P due to the conductor is obtained from principle of superposition by considering the contribution from all current elements I dl.

54. Which among the following statement is correct

1. Electric current is not a scalar quantity. It is a vector quantity. But electric current in a conductor has direction of flow. Therefore, the electric current flowing in a small elemental conductor can be taken as scalar quantity i.e. Idl.
2. Electric and magnetic fields both obey inverse square law, so they are long range fields and obey the principle of superposition and are linear with respect to source. In magnitude, E α q. B α Idl.
3. Only 1
4. Only 2
5. Both 1 and 2
6. None

Explanation

Electric current is not a vector quantity. It is a scalar quantity. But electric current in a conductor has direction of flow. Therefore, the electric current flowing in a small elemental conductor can be taken as vector quantity i.e., Idl.

55. Which among the following statement is incorrect regarding electric field?

1. Produced by a scalar source i.e., an electric charge q
2. It is directed perpendicular to the position vector ρ r and the current element Idl
3. Does not depend on angle
4. None of the above

Explanation

Electric field is 1. Produced by a scalar source i.e., an electric charge q, 2. It is directed along the position vector joining the source and the point at which the field is calculated and 3. Does not depend on angle.

56. Which among the following statement is incorrect regarding magnetic field?

1. Produced by a vector source i.e., current element I dl.
2. It is directed perpendicular to the position vector r and the current element Idl.
3. Depends on the angle between the position vector r and the current element Idl.
4. None of the above

Explanation

Magnetic field is 1. Produced by a vector source i.e., current element I dl, 2. It is directed perpendicular to the position vector r and the current element Idl and 3. Depends on the angle between the position vector r and the current element Idl.

57. Which is a device used to detect very small currents?

1. Capacitance meter
2. Tangent Multimeter
3. Tangent Galvanometer
4. Tangent Ohmmeter

Explanation

Tangent galvanometer is a device used to detect very small currents. It is a moving magnet type galvanometer. Its working is based on tangent law.

58. Which among the following statement is correct regarding tangent law

1. When a magnetic needle or magnet is freely suspended in two mutually perpendicular uniform magnetic fields, it will come to motion in the direction of the resultant of the two fields.
2. Let B be the magnetic field produced by passing current through the coil of the tangent galvanometer and BH be the horizontal component of Earth’s magnetic field. Under the action of two magnetic fields, the needle comes to rest making angle θ with B_H, such that B = B_H tan θ.
3. Only 1
4. Only 2
5. Both 1 and 2
6. None

Explanation

When a magnetic needle or magnet is freely suspended in two mutually perpendicular uniform magnetic fields, it will come to rest in the direction of the resultant of the two fields.

59. Which among the following statement is correct regarding Tangent Galvanometer?

1. Tangent Galvanometer (TG) consists of iron coil of several turns wound on a non-magnetic circular frame. The frame is made up of nickel or mica which is mounted vertically on a horizontal base table (turn table) with four levelling screws. The TG is provided with two or more coils of different number of turns.
2. Most of the equipment’s we use in laboratory, contains coils of 2 turns, 5 turns and 50 turns which are of different thickness and are used for measuring currents of different strengths. At the centre of turn table, there is a small upright projection on which a compass box is placed. Compass box consists of a small magnetic needle which is pivoted at its centre, such that the centres of both magnetic needle and circular coil exactly coincide.
3. A thin aluminium pointer attached perpendicular to the magnetic needle moves over a graduated circular scale. The circular scale is divided into four quadrants and they are graduated in degrees, each quadrant being numbered from 0° to 90° In order to avoid parallax error in measurement, a mirror is placed below the aluminium pointer.
4. Both 1 and 2
5. Both 1 and 3
6. Both 2 and 3
7. All 1, 2 and 3

Explanation

Tangent Galvanometer (TG) consists of copper coil of several turns wound on a non-magnetic circular frame. The frame is made up of brass or wood which is mounted vertically on a horizontal base table (turn table) with three levelling screws. The TG is provided with two or more coils of different number of turns.

60. Which among the following statement is correct regarding precautions of Tangent galvanometer

1. All the nearby magnets and magnetic materials are kept away from the instrument. Using spirit level, the levelling screws at the base are adjusted so that the small magnetic needle is exactly horizontal and also coil (mounted on the frame) is exactly vertical.
2. The plane of the coil is kept parallel to the small magnetic needle by rotating the coil about its vertical axis. So that, the coil remains in magnetic meridian. The compass box alone is rotated such that the aluminium pointer reads 0^o – 0^o.
3. Only 1
4. Only 2
5. Both 1 and 2
6. None

61. Which among the following statement is correct

1. In the tangent galvanometer experiment, when no current is passed through the coil, the small magnetic needle lies along horizontal component of Earth’s magnetic field. When the circuit is closed, the electric current will pass through the circular coil and produce magnetic field at the centre of the coil.
2. Now there are two fields which are acting mutually perpendicular to each other. They are: (1) the magnetic field (B) due to the electric current in the coil acting normal to the plane of the coil. (2) the horizontal component of Earth’s magnetic field (BH)
3. Because of these crossed fields, the pivoted magnetic needle deflects through an angle θ. From tangent law, B = B_H tan θ. When an electric current is passed through a circular coil of radius R having N turns, the magnitude of magnetic field at the centre is B = µ₀. By equating both equation, The horizontal component of Earth’s magnetic field is given by B_H = .
4. Both 1 and 2
5. Both 1 and 3
6. Both 2 and 3
7. All 1, 2 and 3

62. A coil of a tangent galvanometer of diameter 0.24 m has 100 turns. If the horizontal component of Earth’s magnetic field is 25 × 10^–6 T then, calculate the current which gives a deflection of 60^o?

1. I = 0.017 A
2. I = 0.082 A
3. I = 0.171 A
4. I = 0.284 A

Explanation

The diameter of the coil is 0.24 m. Therefore, radius of the coil is 0.12 m.

Number of turns is 100 turns. Earth’s magnetic field is 25 × 10^–6 T Deflection is

θ = 60⁰ 🡪 tan 60⁰ = = 1.732

I = tan θ

=

= 0.82 10^-1 A

= 0.082 A.

63. Which among the following statement is correct

1. The magnetic field at a point on the axis of the current-carrying circular loop of radius R at a distance z from its centre is given by B = K. At larger distance z >> R, therefore R²+Z ² ≈ Z², we have B = K.
2. Let A be the area of the circular loop A = π R2. So, rewriting the equation in terms of area of the loop, we have B = K. Comparing both we get p_m = I A. where pm is called magnetic dipole moment.
3. This implies that a current carrying circular loop behaves as a magnetic dipole of magnetic moment p_m. So, the magnetic dipole moment of any current loop is equal to the product of the current and area of the loop.
4. Both 1 and 2
5. Both 1 and 3
6. Both 2 and 3
7. All 1, 2 and 3

64. If we curl the fingers of right hand in the direction of current in the loop, then the stretched thumb gives which direction in Right hand thumb rule?

1. Electric flux
2. Magnetic flux
3. Magnetic moment
4. Magnetic current

Explanation

In order to determine the direction of magnetic moment, we use right hand thumb rule which states that If we curl the fingers of right hand in the direction of current in the loop, then the stretched thumb gives the direction of the magnetic moment associated with the loop.

65. µ_B = = 9.27 × 10^-24 is called Bohr magneton which is used to measure ____

1. Electric magnetic moments
2. Base magnetic moments
3. Atomic magnet moments
4. Pile magnet moments

Explanation

µ_B = = 9.27 × 10^-24 is called Bohr magneton which is used to measure atomic magnetic moments.

66. Which law is used to calculate magnetic field at a point whenever there is a symmetry in the problem?

1. Joules circuital law
2. Watt circuital law
3. Amperes circuital law
4. Weber circuital law

Explanation

Ampère’s circuital law is used to calculate magnetic field at a point whenever there is a symmetry in the problem. This is similar to Gauss’s law in electrostatics.

67. Ampère’s law: The line integral of magnetic field over a closed loop is what times net current enclosed by the loop?

1. μ₀
2. μ₀ / A
3. μ₀ A²
4. μ₀ A

Explanation

Ampère’s law: The line integral of magnetic field over a closed loop is μ₀ times net current enclosed by the loop. where I_enclosed is the net current linked by the closed loop C. Note that the line integral does not depend on the shape of the path or the position of the conductor with the magnetic field.

68. Which among the following statement is correct regarding Magnetic field due to the current carrying wire of infinite length using Ampère’s law?

1. Consider a straight conductor of infinite length carrying current I and the direction of magnetic field lines. Since the wire is geometrically cylindrical in shape and symmetrical about its axis, we construct an Ampèrian loop in the form of a linea shape at a distance r from one end of the conductor.
2. From the Ampère’s law, we get = μ₀ I. where dl is the line element along the Amperian loop (tangent to the circular loop). Hence, the angle between magnetic field vector and line element is zero.
3. where I is the current enclosed by the Ampèrian loop. Due to the symmetry, the magnitude of the magnetic field is uniform over the Ampèrian loop. Hence = μ₀ I. For a circular loop, the circumference is 2πr, which implies, = μ₀ I. which gives B = .
4. Both 1 and 2
5. Both 1 and 3
6. Both 2 and 3
7. All 1, 2 and 3

Explanation

Consider a straight conductor of infinite length carrying current I and the direction of magnetic field lines. Since the wire is geometrically cylindrical in shape and symmetrical about its axis, we construct an Ampèrian loop in the form of a circular shape at a distance r from the centre of the conductor.

69. Compute the magnitude of the magnetic field of a long, straight wire carrying a current of 1 A at distance of 1m from it. Compare it with Earth’s magnetic field?

1. B_straightwire is one hundred times smaller than B_Earth.
2. B_straightwire is one thousand times smaller than B_Earth.
3. B_straightwire is one hundred times larger than B_Earth.
4. B_straightwire is one thousand times larger than B_Earth.

Explanation

Given that I = 1 A and radius r = 1 m

B_straightwire = = = 2 10^-7 T.

But the Earth’s magnetic field is B_Earth : 10⁻⁵ T.

So, B_straightwire is one hundred times smaller than B_Earth.

70. Which is a long coil of wire closely wound in the form of helix and When electric current is passed through the solenoid, the magnetic field is produced?

1. Resonance
2. Flux
3. Lorentz
4. Solenoid

Explanation

A solenoid is a long coil of wire closely wound in the form of helix. When electric current is passed through the solenoid, the magnetic field is produced.

71. The direction of magnetic field due to solenoid is given by which rule?

1. Joules law
2. Right hand thumb rule
3. Right hand palm rule
4. Left hand thumb rule

Explanation

The magnetic field of the solenoid is due to the superposition of magnetic fields of each turn of the solenoid. The direction of magnetic field due to solenoid is given by right hand palm-rule.

72. Inside the solenoid, the magnetic field is nearly uniform and parallel to its axis whereas, outside the solenoid the field is negligibly ____

1. Very large
2. Large
3. Small
4. Uniform

Explanation

Inside the solenoid, the magnetic field is nearly uniform and parallel to its axis whereas, outside the solenoid the field is negligibly small. Based on the direction of the current, one end of the solenoid behaves like North Pole and the other end behaves like South Pole.

73. The current carrying solenoid is held in right hand. If the fingers curl in the direction of current, then extended thumb gives the direction of ___

1. Magnetic moment
2. Magnetic flux
3. Electric flux
4. Magnetic field

Explanation

The current carrying solenoid is held in right hand. If the fingers curl in the direction of current, then extended thumb gives the direction of magnetic field of current carrying solenoid.

74. Which among the following statement is correct

1. The length of the solenoid is larger when compared to its diameter.
2. The length of the solenoid is equal to its diameter.
3. The winding of solenoid must be always circular
4. All the above

Explanation

The solenoid is assumed to be long which means that the length of the solenoid is large when compared to its diameter. The winding need not to be always circular, it can also be in other shapes. We consider here only circularly wound solenoid.

75. What is the unit of magnetic flux?

1. T m
2. T m²
3. T m^-2
4. T m^-1

Explanation

The SI unit of magnetic flux is T m². It is also measured in weber or Wb. 1 Wb = 1 T m².

76. Which among the following statement is incorrect?

1. The magnetic flux FB through an area A in a magnetic field is defined as the number of magnetic momentum lines passing through that area perpendicularly and is given by the equation Φ_B = .dA.
2. where the integral is taken over the area A and θ is the angle between the direction of the magnetic field and the outward normal to the area. If the magnetic field B ­‑ is uniform over the area A and is perpendicular to the area, then the above equation becomes Φ_B = .dA = BA cos θ = BA (since θ = 0⁰, cos 0⁰ = 1).
3. Only 1
4. Only 2
5. Both 1 and 2
6. None

Explanation

The magnetic flux FB through an area A in a magnetic field is defined as the number of magnetic field lines passing through that area normally and is given by the equation Φ_B = .dA.

77. A circular antenna of area 3 m² is installed at a place in Madurai. The plane of the area of antenna is inclined at 47^o with the direction of Earth’s magnetic field. If the magnitude of Earth’s field at that place is 4.1 × 10^–5 T find the magnetic flux linked with the antenna?

1. Φ_B = 78.46 µWb
2. Φ_B = 78.28 µWb
3. Φ_B = 82.69 µWb
4. Φ_B = 89.96 µWb

Explanation

B = 4.1 × 10^–5 T; θ = 90^o – 47^o = 43° ; A = 3m²

Φ_B = BA cosθ

= 4.1 × 10^–5 × 3 × cos 43^o

= 4.1 × 10^–5 × 3 × 0.7314

= 89.96 µWb

78. Which among the following statement is correct regarding first Faraday’s Experiments on Electromagnetic Induction?

1. Consider a closed circuit consisting of a coil C of insulated wire and a galvanometer G. The galvanometer does not indicate deflection as there is no electric current in the circuit. When a bar magnet is inserted into the stationary coil, with its north pole facing the coil, there is a momentary deflection in the galvanometer.
2. This indicates that an electric current is set up in the coil. If the magnet is kept stationary inside the coil, the galvanometer does not indicate deflection. The bar magnet is now withdrawn from the coil, the galvanometer again gives a momentary deflection but in the opposite direction. So, the electric current flows in opposite direction. Now if the magnet is moved faster, it gives a larger deflection due to a greater current in the circuit
3. The bar magnet is reversed i.e., the south pole now opposes the coil. When the above experiment is repeated, the deflections are opposite to that obtained in the case of north pole. It is concluded that whenever there is a relative motion between the coil and the magnet, there is no deflection in the galvanometer, indicating the electric current setup in the coil.
4. Both 1 and 2
5. Both 1 and 3
6. Both 2 and 3
7. All 1, 2 and 3

Explanation

The bar magnet is reversed i.e., the south pole now faces the coil. When the above experiment is repeated, the deflections are opposite to that obtained in the case of north pole. If the magnet is kept stationary and the coil is moved towards or away from the coil, similar results are obtained. It is concluded that whenever there is a relative motion between the coil and the magnet, there is deflection in the galvanometer, indicating the electric current setup in the coil.

79. A circular loop of area 5 × 10^–2 m² rotates in a uniform magnetic field of 0.2T. If the loop rotates about its diameter which is perpendicular to the magnetic field as shown in figure. Find the magnetic flux linked with the loop when its plane is (i) normal to the field (ii) inclined 60^o to the field and (iii) parallel to the field.

1. (i) Φ_B = 2 × 10^-2 Wb; (ii) Φ_B = 8.66 × 10^-3 Wb; (iii) Φ_B = 1 × 10^-2 Wb
2. (i) Φ_B = 0; (ii) Φ_B = 1.66 × 10^-3 Wb; (iii) Φ_B = 1 × 10^-2 Wb
3. (i) Φ_B = 1 × 10^-2 Wb; (ii) Φ_B = 8.66 × 10^-3 Wb; (iii) Φ_B = 0
4. (i) Φ_B = 2 × 10^-2 Wb; (ii) Φ_B = 1.66 × 10^-3 Wb; (iii) Φ_B = 0

Explanation

A = 5× 10^–2 m² ; B = 0.2 T

(i) θ = 0°; Φ_B = BA cosθ

= 0.2 × 5 × 10^-2 × cos 0⁰

Φ_B = 1 × 10^-2 Wb

(ii) θ = 90° – 60° = 30°

Φ_B = BA cosθ = 0.2 × 5 × 10^-2 × cos 30⁰

= 1 × 10^-2 ×

Φ_B = 8.66 × 10^-3

(iii) θ = 90°; Φ_B = BA cosθ

Φ_B = O.2 × 5 × 10^-2 × cos 90⁰

Φ_B = 0

80. Which among the following statement is correct regarding Second Experiment of Faraday’s Experiments on Electromagnetic Induction?

1. Consider two closed circuits. The circuit consisting of a coil P, a battery B and a key K is called as primary circuit while the circuit with a coil S and a galvanometer G is known as secondary circuit. The coils P and S are kept at rest in close proximity with respect to one another. If the primary circuit is closed, electric current starts flowing in the primary circuit.
2. At that time, the galvanometer gives a momentary deflection. After that, when the electric current reaches a certain steady value, no deflection is observed in the galvanometer. Likewise, if the primary circuit is broken, the electric current starts decreasing and there is again a sudden deflection but in the opposite direction.
3. When the electric current becomes zero, the galvanometer shows no deflection. From the above observations, it is concluded that whenever the electric current in the primary circuit changes, the galvanometer shows a deflection.
4. Both 1 and 2
5. Both 1 and 3
6. Both 2 and 3
7. All 1, 2 and 3

81. From which of the following the magnetism word was derived historically?

a) Fe3O4

b) Fe

c) Fe O4

d) Fe₂

Explanation

Historically the word ‘magnetism’ was derived from iron ore magnetite (Fe3O4). In olden days, magnets were used as magnetic compass for navigation, magnetic therapy for treatment and also used in magic shows.

82. According to Gover suggestion which is responsible for the Earth’s magnetic field?

a) Plate movements of the Earth

b) Rotation and revolution of Earth

c) Hot rays from the Sun

d) Magnetic coupling effect of other planets

Explanation

Gover suggested that the Earth’s magnetic field is due to hot rays coming out from the Sun. These rays will heat up the air near equatorial region. Once air becomes hotter, it rises above and will move towards northern and southern hemispheres and get electrified. This may be responsible to magnetize the ferromagnetic materials near the Earth’s surface.

83. The Geographic equator is ____ to the Earth’s geographic axis.

a) Equal

b) Perpendicular

c) Along

d) Parallel

Explanation

A great circle perpendicular to Earth’s geographic axis is called geographic equator.

84. In which of these regions the magnetic deflection is smaller?

a) Near the equator

b) Near the poles

c) At lower latitudes

d) Higher Longitudes

Explanation

At higher latitudes, the declination is greater whereas near the equator, the declination is smaller. In India, declination angle is very small and for Chennai, magnetic declination angle is –1o 16ʹ (which is negative (west)).

85. Choose the correct statements.

i) Earth’s magnetic field can be resolved into four components on its surface.

ii) The horizontal component is the cos value of the net magnetic field of Earth.

a) i only

b) ii only

c) Both i and ii

d) Neither i nor ii

Explanation

Let BE be the net Earth’s magnetic field at any point on the surface of the Earth. BE can be resolved into two perpendicular components. Horizontal component BH = BE cos I and Vertical component BV = BE sin I

86. Which of the component of Earth magnetic field is zero at the poles?

a) Horizontal component

b) Tangential component

c) Vertical component

d) All the above

Explanation

The Earth’s magnetic field is perpendicular to the surface of the Earth (i.e., vertical) which implies that the needle of magnetic compass rests vertically at an angle of dip, I = 90o. Hence,

BH = 0 ,BV = BE

This implies that the vertical component is maximum at poles and horizontal component is zero at poles.

87. Which of these is the reason for the blue or purplish-red aurora?

a) Ionized oxygen

b) Ionized suphur

c) Ionized nitrogen

d) Ionized carbon

Explanation

“Aurora borealis” in the north and “Aurora australis” in the south. This occurs as a result of interaction between the gaseous particles in the Earth’s atmosphere with highly charged particles released from the Sun’s atmosphere through solar wind. A pale yellowish – green colour is produced when the ionized oxygen takes part in the collision and a blue or purplish – red aurora is produced due to ionized nitrogen molecules.

88. What is the SI unit of the magnetic moment?

a) Am²

b) Am

c) As^-1

d) Am³

Explanation

The SI unit of magnetic moment is A m2. The direction of magnetic moment is from south pole to north pole.

89. Choose the correct statements.

i) Magnets are classified into various types base on the strength.

ii) Natural magnets are very strong and irregular in shape.

iii) Artificial magnets have the desired shape and strength.

a) i only

b) ii only

c) iii only

d) All the above

Explanation

Magnets are classified into natural magnets and artificial magnets. For example, iron, cobalt, nickel, etc. are natural magnets. Strengths of natural magnets are very weak and the shapes of the magnet are irregular. Artificial magnets are made in order to have desired shape and strength.

90. What is the ratio of the magnetic length and geometric length?

a) 5/7

b) 5/6

c) 6/11

d) 6/5

Explanation

The length of the bar magnet is called geometrical length and the length between two magnetic poles in a bar magnet is called magnetic length. Magnetic length is always slightly smaller than geometrical length. The ratio of magnetic length and geometrical length is 5/6.

91. Which of these value is not dependent on the pole strength?

a) Nature of materials

b) Area of cross section

c) Shape of the material

d) State of magnetization

Explanation

Pole strength is a scalar quantity. north pole of a magnet experiences a force in the direction of magnetic field while south pole of a magnet experiences force opposite to the magnetic field. Pole strength depends on the nature of materials of the magnet, area of crosssection and the state of magnetization.

92. Choose the Incorrect statements.

i) The pole strength is reduced to half when the magnet is cut into two equal halves along the length.

ii) If a magnet is cut into two equal halves perpendicular to the length, pole strength is doubled.

iii) Isolated monopole does not exist in nature.

a) i only

b) ii only

c) iii only

d) All the above

Explanation

If a magnet is cut into two equal halves along the length then pole strength is reduced to half. If a magnet is cut into two equal halves perpendicular to the length, then pole strength remains same. If a magnet is cut into two pieces, we will not get separate north and south poles. Instead, we get two magnets. In other words, isolated monopole does not exist in nature

92. Which of the following value is directly proportional to the force of attracttion or repulsion?

a) Product of their pole strength

b) Distance between the poles.

c) Square of the pole strength

d) Square of the distance between the poles.

Explanation

The force of attraction or repulsion between two magnetic poles is directly proportional to the product of their pole strengths and inversely proportional to the square of the distance between them.

93. Which of the following does not differentiate the magnetic material from another material?

a) Magnetic susceptibility

b) Magetic momentum

c) Intensity of magnetization

d) Magnetic induction

Explanation

In order to differentiate one magnetic material from another, some basic parameters are used. they are: Magnetising field, Magnetic permeability, Intensity of magnetization, Magnetic induction or Total magnetic field and Magnetic susceptibility

94. What is the value of relative eperimiability in freee space?

a) 1

b) Zero

c) Negative value

d) Real integer

Explanation

Relative permeability is a dimensionless number and has no units. For free space (air or vacuum), the relative permeability is unity i.e., μr = 1.

95. Whch is known as the net magnetic moment per unit volume of the material?

a) Intensity of magnetization

b) Volumatic strength

c) Density of magnets

d) Magnetic strength

Explpantion

The net magnetic moment per unit volume of the material is known as intensity of magnetisation. It is a vector quantity.

96. Which of these value is denoted by the magnetic susceptibility?

a) Magnetization intensity

b) Total value of induced magnetism

c) Material response to external magnetic field.

d) Approximate value of net magnetic field.

Explanation

When a substance is kept in a magnetising field H, magnetic susceptibility gives information about how a material responds to the external (applied) magnetic field. In other words, the magnetic susceptibility measures how easily and how strongly a material can be magnetized.

97. What is the magnetic susceptibility value of oxygen?

a) 2090 x 10^-9

b) -2.2 x 10^-5

c) 7.06 x 10^-5

d) 2.9 x 10^-5

Explanation

98. How many types of materials are classified based on their behavior in a magnetizing field?

a) 5

b) 4

c) 3

d) 2

Explanation

The magnetic materials are generally classified into three types based on their behaviour in a magnetising field. They are diamagnetic, paramagnetic and ferromagnetic materials

99. Which of the following is not a diamagnetic material?

a) Bismuth

b) Oxygen

c) Copper

d) Water

Explanation

When placed in a non-uniform magnetic field, the interaction between induced magnetic moment and the external field creates a force which tends to move the material from stronger part to weaker part of the external field. It means that diamagnetic material is repelled by the field. This action is called diamagnetic action and such materials are known as diamagnetic materials. Examples: Bismuth, Copper and Water etc.

100. Which of the following is not a property of diamagnetic material?

a) Magnetic susceptibility is negative.

b) Relative permeability is more than unity.

c) Magnetic field lines are repelled or expelled.

d) Susceptibility is nearly temperature independent.

Explanation

The properties of diamagnetic materials are, Magnetic susceptibility is negative. Relative permeability is slightly less than unity. The magnetic field lines are repelled or expelled by diamagnetic materials when placed in a magnetic field. Susceptibility is nearly temperature independent.

101. Choose the incorrect statements.

i) Superconductors are perfect paramagnetic materials.

ii) The Meissner effect is the expulsion of magnetic flux from a superconductor during its transition.

a) i only

b) ii only

c) Both i and ii

d) Neither i nor ii

Explanation

Superconductors are perfect diamagnetic materials. The expulsion of magnetic flux from a superconductor during its transition to the superconducting state is known as Meissner effect

101. Which of the following is not an advantage of Maglev train?

a) Quieter than conventional

b) Cost effective

c) Environment friendly

d) High speed

Explanation

Maglev train does not need wheels and also achieve greater speed. The basic mechanism of working of Maglev train involves two sets of magnets. One set is used to repel which makes train to float above the track and another set is used to move the floating train ahead at very great speed. These trains are quieter, smoother and environmental friendly compared conventional trains and have potential for moving with much higher speeds with technology in future.

102. Which of the following is not a paramagnetic material?

a) Aluminium

b) Copper

c) Oxygen

d) Platinum

Explanation

Materials which exhibit weak magnetism in the direction of the applied field are known as paramagnetic materials. Examples: Aluminium, Platinum, Chromium and Oxygen etc.

103. According to the Curie’s law magnetic susceptibility is affected by _____.

a) Pressure

b) Magnetic strength

c) Pole strength

d) Temperature

Explanation

Curie’s law : When temperature is increased, thermal vibration will upset the alignment of magnetic dipole moments. Therefore, the magnetic susceptibility decreases with increase in temperature.

104. Choose the Incorrect statements.

i) Materials exhibiting strong magnetism in the opposite direction of applied field are called ferromagnetic materials.

ii) Iron, Nickel and Cobalt are ferromagnetic materials.

a) i only

b) ii only

c) Both i and ii

d) Neither i nor ii

Explanation

Materials which exhibit strong magnetism in the direction of applied field are called ferromagnetic materials. Examples: Iron, Nickel and Cobalt.

105. Which of these materials have large and positive magnetic susceptibility?

a) Diamagnetic

b) Para magnetic

c) Ferro magnetic

d) All the above

Explanation

The properties of ferromagnetic materials are: Magnetic susceptibility is positive and large. Relative permeability is large. The magnetic field lines are strongly attracted into the ferromagnetic materials when placed in a magnetic field. Susceptibility is inversely proportional to temperature.

106. Which of the following statement is not correct regarding spin?

a) Spin is an important attribute for an elementary particle.

b) Spin is a quantum mechanical phenomenon responsible for magnetic properties of the material.

c) Spin in quantum mechanics means rotation as in the classical mechanics.

d) Spin is intrinsic angular momentum does not have classical analogue.

Explanation

Like mass and charge for particles, spin is also another important attribute for an elementary particle. Spin is a quantum mechanical phenomenon which is responsible for magnetic properties of the material. Spin in quantum mechanics is entirely different from spin we encounter in classical mechanics. Spin in quantum mechanics does not mean rotation; it is intrinsic angular momentum which does not have classical analogue.

107. Which of the following are the properties of soft ferromagnetic material?

i) Large loop area.

ii) high susceptibility and magnetic permeability.

iii) Low retentivity.

iv) More hysteresis loss.

v) Used as permanent magnet.

a) ii, iii only

b) i, iii, v only

c) iv, v only

d) i, iv, v only

Explanation

108. Choose the correct statements.

i) Electric current is a vector quantity.

ii) Electric current in a conductor has direction of flow.

a) i only

b) ii only

c) Both i and ii

d) Neither i nor ii

Explanation

Electric current is not a vector quantity. It is a scalar quantity. But electric current in a conductor has direction of flow. Therefore, the electric current flowing in a small elemental conductor can be taken as vector quantity.

109. Which of the following statements are not true regarding the magnetic field?

a) Directed perpendicularly to the position vector and current element.

b) Depends on the angle between the position vector and current element.

c) Produced by a scalar source.

d) Current element produces magnetic field.

Explanation

110. Define MRI.

a) Magnetic Resonance Imaging

b) Magnetic Reciprocal Index

c) Magnetic Response Intensity

d) Magnetic Refractive Index

Explanation

MRI is Magnetic Resonance Imaging which helps the physicians to diagonise or monitor treatment for a variety of abnormal conditions happening within the head, chest, abdomen and pelvis. It is a non invasive medical test.

111. Which of the following statement is not true regarding the solenoid?

i) A Toroid is a solenoidal ends joined together to form a closed ring shape.

ii) The magnetic field is variable magnitude inside the toroid.

iii) The interior region and exterior region of the toroid has zero magnetic field.

a) i only

b) ii only

c) iii only

d) All the above

Explanation

A solenoid is bent in such a way its ends are joined together to form a closed ring shape, is called a toroid. The magnetic field has constant magnitude inside the toroid whereas in the interior region (say, at point P) and exterior region (say, at point Q), the magnetic field is zero.

112. Which of the following is used to accelerate the charged particles to gain large kinetic energy?

a) Solenid

b) Deutron

c) Cyclotron

d) Toroid

Explanation

Cyclotron is a device used to accelerate the charged particles to gain large kinetic energy. It is also called as high energy accelerator. It was invented by Lawrence and Livingston in 1934.

113. Choose the correct statements.

i) Deutron arebundles of two proton and two neutrons.

ii) Neutron cannot be accelerated by the cyclotron.

a) i only

b) ii only

c) Both i and ii

d) Neither i nor ii

Explanation

Deutrons (bundles of one proton and one neutron) can be accelerated because it has same charge as that of proton. But neutron (electrically neutral particle) cannot be accelerated by the cyclotron.

114. What is the usage of moving coil galavanometer?

a) To detect the flow of current in an electrical circuit.

b) To calculate the net magnetic strength.

c) To calculate the angular momentum of particles.

d) To identify the voltage difference.

Explanation

Moving coil galvanometer is a device which is used to detect the flow of current in an electrical circuit.

115. Choose the correct statements.

i) Galvanometer is very sensitive instrument to detect the voltage.

ii) Galavanometer can be easily converted into ammeter.

a) i only

b) ii only

c) Both i and ii

d) Neither i nor ii

Explanation

A galvanometer is very sensitive instrument to detect the current. It can be easily converted into ammeter and voltmeter.

12th Science Lesson 9 Questions in English

9] Ray Optics

1. Which of the following statement is correct?

1. Light is difficult to comprehend light to a single entity
2. It has both ray and wave property
3. Ray optics deals with light that is represented as a ray travelling in straight lines
4. 1, 2
5. 2, 3
6. 1, 3
7. 2, 3
8. All the above

Explanation

Light is mystical. Yet, its behaviour is so fascinating. It is difficult to comprehend light to a single entity. In this unit, we learn it in two different scientific aspects called ray optics and wave optics. Ray optics deals with light that is represented as a ray travelling in straight lines. In wave optics, we study about the phenomenon associated with the propagation of light as a wave.

2. Which of the following statement is incorrect?

1. Light travels in a straight line in a medium
2. Light does not deviate from its path when it encounters another medium or an obstacle
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Light travels in a straight line in a medium. Light may deviate in its path only when it encounters another medium or an obstacle.

3. Which of the following statement is correct?

1. A ray of light gives information about only the direction of light.
2. It gives information about the other characteristics of light like intensity and colour
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

A ray of light gives information about only the direction of light. It does not give information about the other characteristics of light like intensity and colour.

4. Which of the following can be understood from ray depiction of light?

1. Reflection
2. Refraction
3. Dispersion
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

The path of the light is called a ray of light and a bundle of such rays is called a beam of light. In this chapter, we can explain the phenomena of reflection, refraction, dispersion and scattering of light, using the ray depiction of light.

5. The bouncing back of light into the same medium is called______

1. Reflection
2. Refraction
3. Dispersion
4. All the above

Explanation

The bouncing back of light into the same medium when it encounters a reflecting surface is called reflection of light.

6. Mirrors which are silver coated at their back can reflect almost ___% of the light falling on them.

1. 70
2. 90
3. 100
4. 80

Explanation

Polished surfaces can reflect light. Mirrors which are silver coated at their back can reflect almost 90% of the light falling on them.

7. Which of the following is correct according to law of reflection?

1. The incident ray, reflected ray and normal to the reflecting surface all are coplanar
2. The angle of incidence i is equal to the angle of reflection r
3. The angle of incidence i is not equal to the angle of reflection r.
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

According to law of reflection,

(a) The incident ray, reflected ray and normal to the reflecting surface all are coplanar (ie. lie in the same plane).

(b) The angle of incidence i is equal to the angle of reflection r

i = r

8. Which of the following statement is incorrect?

1. The law of reflection is valid at each point for any reflecting surface whether the surface is plane or curved
2. The angle between the incident and deviated light ray is called angle of deviation of the light ray.
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

The law of reflection is valid at each point for any reflecting surface whether the surface is plane or curved. The angle between the incident and deviated light ray is called angle of deviation of the light ray.

9. Which of the following statement is correct?

1. If the reflecting surface is flat, then incident parallel rays after reflection come out parallel as per the law of reflection.
2. If the reflecting surface is irregular, then the incident parallel rays after reflection come out irregular rays
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

If the reflecting surface is flat, then incident parallel rays after reflection come out parallel as per the law of reflection. If the reflecting surface is irregular, then the incident parallel rays after reflection come out irregular (not parallel) rays.

10. Which of the following can be use to find angle of deviation?

1. d = 180 – 2i
2. d = 180 + 2i
3. d = 90 – 2i
4. d = 180 – i

Explanation

The angle between the incident and deviated light ray is called angle of deviation of the light ray. The incident light is AO. The reflected light is OB. The un-deviated light is OC which is the continuation of the incident light. The angle between OB and OC is the angle of deviation d. From the geometry, it is written as, d = 180 – (i+r). As, i = r in reflection, we can write angle of deviation in reflection at plane surface as,

d = 180 – 2i

11. When a real object is placed at a point O in front of a plane mirror it produces divergent rays in__

1. Opposite direction
2. Same direction
3. All direction
4. None

Explanation

When a real object is placed at a point O in front of a plane mirror it produces divergent rays in all directions as shown in Figure

12. Image which cannot be formed on the screen but can only be seen with the eyes is called____

1. Real image
2. Virtual image
3. Both a and b
4. None

Explanation

After reflection from the plane mirror, they appear to come out from a point I behind the mirror. This image cannot be formed on a screen as the image is behind the mirror. This type of image which cannot be formed on the screen but can only be seen with the eyes is called virtual image

13. Image which can be formed on a screen and can also be seen with the eyes is called______

1. Real image
2. Virtual image
3. Both a and b
4. Either a or b

Explanation

On the other hand, if convergent rays are incident on a plane mirror, the rays after reflection pass through a point I in front of the mirror and form an image as shown in Figure. This image can be formed on a screen as the image is in front of the mirror. This type of image which can be formed on a screen and can also be seen with the eyes is called real image.

14. It is generally known that a plane mirror can only form a______

1. Real image
2. Virtual image
3. Both a and b

Either a or b

Explanation

It is generally known that a plane mirror can only form a virtual image. But now we have understood that a plane mirror can form a real image when converging rays fall on it.

15. Match the following

A.Real Image 1. Rays appear to converge at the object

B.Virtual Image 2. Rays actually diverge from the object

C.Real Object 3. Rays appear to diverge from the image

D.Virtual Object 4. Rays actually converge at the image

1. 2, 1, 3, 4
2. 1, 3, 2, 4
3. 4, 3, 2, 1
4. 4, 2, 1, 3

Explanation

16. Which of the following statement is correct?

1. A spherical surface is a part cut from a hollow sphere.
2. Spherical mirrors are generally constructed from glass
3. Both the surface of the glass is silvered.
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

A spherical surface is a part cut from a hollow sphere. Spherical mirrors are generally constructed from glass. One surface of the glass is silvered. The reflection takes place at the other polished surface.

17. Which of the following statement is correct?

1. If the reflection takes place at the convex surface, it is called a convex mirror
2. If the reflection takes place at the concave surface, it is called a concave lens
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

If the reflection takes place at the convex surface, it is called a convex mirror and if the reflection takes place at the concave surface, it is called a concave mirror.

18. The middle point on the spherical surface of the mirror is called as____

1. Radius of curvature
2. Pole
3. Focus
4. Principal axis

Explanation

The radius of the sphere of which the spherical mirror is a part is called the radius of curvature (R) of the mirror. The middle point on the spherical surface of the mirror (or) the geometrical centre of the mirror is called pole (P) of the mirror.

19. The line joining the pole and the centre of curvature is called_____

1. Radius of curvature
2. Pole
3. Focus
4. Principal axis

Explanation

The line joining the pole and the centre of curvature is called the principal axis of the mirror. The light ray travelling along the principal axis towards the mirror after reflection travels back along the same principal axis. It is also called optical axis.

20. Which of the following statement is correct?

1. Light rays travelling parallel and close to the principal axis when incident on a spherical mirror, converge at a point for concave mirror or appear to diverge from a point for convex mirror on the principal axis
2. This point is called the focus or focal point (F) of the mirror.
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Light rays travelling parallel and close to the principal axis when incident on a spherical mirror, converge at a point for concave mirror or appear to diverge from a point for convex mirror on the principal axis. This point is called the focus or focal point (F) of the mirror.

21. The distance between the pole and the focus is called______

1. Centre of curvature
2. Radius of curvature
3. Focal length
4. Pole length

Explanation

The distance between the pole and the focus is called the focal length (f) of the mirror. The plane through the focus and perpendicular to the principal axis is called the focal plane of the mirror.

22. Which of the following statement is correct?

1. The rays travelling very close to the principal axis and make small angles with it are called paraxial rays
2. The paraxial rays fall on the mirror very close to the pole of the mirror
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

The rays travelling very close to the principal axis and make small angles with it are called paraxial rays. The paraxial rays fall on the mirror very close to the pole of the mirror.

23. Which of the following statement is incorrect?

1. The rays travelling far away from the principal axis and fall on the mirror far away from the pole are called as marginal rays
2. Paraxial rays and marginal rays behave differently
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

On the other hand, the rays travelling far away from the principal axis and fall on the mirror far away from the pole are called as marginal rays. Both Paraxial rays and marginal rays behave differently (get focused at different points).

24. Radius of curvature is equal to____

1. 2f
2. f
3. f/2
4. 3f

Explanation

PF is focal length f and PC is the radius of curvature R.

25. Which of the following statement is correct?

1. A ray parallel to the principal axis after reflection will pass through or appear to pass through the principal focus.
2. A ray passing through or appear to pass through the principal focus, after reflection will travel parallel to the principal axis.
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

A ray parallel to the principal axis after reflection will pass through or appear to pass through the principal focus. A ray passing through or appear to pass through the principal focus, after reflection will travel parallel to the principal axis.

26. Which of the following statement is incorrect?

1. A ray passing through the centre of curvature retraces its path after reflection as it is a case of normal incidence
2. A ray falling on the pole will get refracted as per law of reflection keeping principal axis as the normal
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

A ray passing through the centre of curvature retraces its path after reflection as it is a case of normal incidence. A ray falling on the pole will get reflected as per law of reflection keeping principal axis as the normal.

27. Match the following cartesian signs

A.u 1. Image height

B.v 2. Object height

C.h 3. Image distance

D.h’ 4. Object distance

1. 1, 2, 3, 4
2. 4, 3, 2, 1
3. 4, 2, 3, 1
4. 2, 1, 3, 4

Explanation

While tracing the image, we would normally come across the object distance u, the image distance v, the object height h, the image height (h′), the focal length f and the radius of curvature R.

28. Which of the following cartesian sign convection is correct?

1. The Incident light is taken from left to right (i.e. object on the left of mirror)
2. All the distances are measured from the pole of the mirror (pole is taken as origin).
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Cartesian sign convention:

The Incident light is taken from left to right (i.e. object on the left of mirror).

All the distances are measured from the pole of the mirror (pole is taken as origin).

29. Which of the following statement about cartesian sign is correct?

1. The distances measured to the right of pole along the principal axis are taken as positive
2. The distances measured to the left of pole along the principal axis are taken as negative.
3. Heights measured in the upward perpendicular direction to the principal axis are taken as negative
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Cartesian sign convention:

The distances measured to the right of pole along the principal axis are taken as positive.

The distances measured to the left of pole along the principal axis are taken as negative.

Heights measured in the upward perpendicular direction to the principal axis are taken as positive.

Heights measured in the downward perpendicular direction to the principal axis, are taken as negative.

30. Which of the following is mirror equation?

1. 1/u + 1/v = – 1/f
2. 1/u + 1/v = 1/f
3. 1/u – 1/v = 1/f
4. 1/u + 1/v = – 1/p

Explanation

The following equation is mirror equation:

31. The lateral or transverse magnification is defined as the ratio of______

1. height of the image to the height of the object
2. height of the object to the height of the image
3. height of the virtual image to the height of the object
4. height of the real image to the height of the virtual image

Explanation

The lateral or transverse magnification is defined as the ratio of the height of the image to the height of the object. Height of the object and image are measured perpendicular to the principal axis

32. An object is placed at a distance of 20.0 cm from a concave mirror of focal length 15.0 cm. What distance from the mirror a screen should be placed to get a sharp image?

1. 60 cm
2. -60 cm
3. 30 cm
4. -30 cm

Explanation

33. An object is placed at a distance of 20.0 cm from a concave mirror of focal length 15.0 cm. What is its magnification?

a) 3

b)– 3

c)1.5

d)– 1.5

Explanation

34. A thin rod of length f/3 is placed along the optical axis of a concave mirror of focal length f such that its image which is real and elongated just touches the rod. Calculate the longitudinal magnification.

1. 1
2. 1.5
3. 2
4. 3

Explanation

35. Which of the following statement is correct?

1. Light travels with the highest speed in vacuum.
2. The speed of light in vacuum is denoted as c and its value is, c = 3×10⁸ ms^-1
3. The earliest attempt to find speed of light was made by a French scientist Hippolyte Fizeau
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Light travels with the highest speed in vacuum. The speed of light in vacuum is denoted as c and its value is, c = 3×108 ms-1. It is a very high value. Several attempts were made by scientists to determine the speed of light. The earliest attempt was made by a French scientist Hippolyte Fizeau (1819– 1896). That paved way for the other scientists too to determine the speed of light.

36. At what angle incident light was made to hit silvered glass in Fizeau’s method to determine speed of light?

1. 30⁰
2. 45⁰
3. 60⁰
4. 90⁰

Explanation

In Fizeau’s method to determine speed of light, e light from the source S was first allowed to fall on a partially silvered glass plate G kept at an angle of 45^o to the incident light from the source.

37. Which of the following statement is correct?

1. Fizeau had some difficulty to visually estimate the minimum intensity of the light when blocked by the adjacent tooth, and his value for speed of light was very close to the actual value
2. Later on, with the same idea of Fizeau and with much sophisticated instruments, the speed of light in air was determined as, v = 2.99792×10⁸ m s^–1
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Fizeau had some difficulty to visually estimate the minimum intensity of the light when blocked by the adjacent tooth, and his value for speed of light was very close to the actual value. Later on, with the same idea of Fizeau and with much sophisticated instruments, the speed of light in air was determined as, v = 2.99792×10⁸ m s^–1.

38. Who introduced Different transparent media like glass, water to find speed of light?

1. Fizeau
2. Einstein
3. Newton
4. Foucault and Michelson

Explanation

Different transparent media like glass, water etc. were introduced in the path of light by scientists like Foucault (1819– 1868) and Michelson (1852–1931) to find the speed of light in different media.

39. Refractive index of a transparent medium is__

1. u/v
2. c/v
3. v/c
4. v/u

Explanation

Refractive index of a transparent medium is defined as the ratio of speed of light in vacuum (or air) to the speed of light in that medium.

40. One type of transparent glass has refractive index 1.5. What is the speed of light through this glass?

1. 2×10⁸ ms^-1
2. 2×10⁸ ms^-2
3. 3×10⁸ ms^-1
4. 2×10⁸ ms³

Explanation

41. The smallest value of refractive index is for vacuum and is_____

1. 0.1
2. 1
3. 0
4. 0.5

Explanation

Refractive index does not have unit. The smallest value of refractive index is for vacuum, which is 1. For any other medium refractive index is greater than 1.

42. ______ is also called as optical density of the medium.

1. Refractive index
2. Pole length
3. Centre of curvature
4. Reflective index

Explanation

Refractive index is also called as optical density of the medium. Higher the refractive index of a medium, greater is its optical density and speed of light through the medium is lesser and vice versa.

43. Match the media with the respective refractive index:

A.Air 1. 1.46

B.Pure water 2. 1.0003

C.Ice 3. 1.31

D.Quartz 4. 1.33

1. 2, 1, 3, 4
2. 2, 4, 3, 1
3. 3, 2, 1, 4
4. 4, 2, 1, 3

Explanation

44. Match the media with the respective refractive index:

A.Gallium phosphide 1. 3.50

B.Diamond 2. 2.16

C.Qubic zirconia 3. 2.42

D.Sapphire 4. 1.77

1. 3, 1, 2, 4
2. 1, 3, 2, 4
3. 1, 2, 4, 3
4. 3, 1, 2, 4

Explanation

45. Light travels from air in to glass slab of thickness 50 cm and refractive index 1.5. What is the speed of light in glass?

1. 2 x 10⁸ m s^-1
2. 3 x 10⁸ m s^-1
   1. x 10⁸ m s^-1
3. 12 x 10⁸ m s^-1

Explanation

46. Light travels from air in to glass slab of thickness 50 cm and refractive index 1.5. What is the time taken by the light to travel through the glass slab?

a) 2.5 x 10^-9 s

b) 3.5 x 10^-9 s

c) 1.5 x 10^-9 s

d) 0.5 x 10^-9 s

Explanation

47. Light travels from air in to glass slab of thickness 50 cm and refractive index 1.5. What is the optical path of the glass slab?

1. 45 cm
2. 75 cm
3. 125 cm
4. 25 cm

Explanation

48. Which of the following statement is correct?

1. Refraction is passing through of light from one optical medium to another optical medium through a boundary
2. Law of refraction is called Snell’s law
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Refraction is passing through of light from one optical medium to another optical medium through a boundary. In refraction, the angle of incidence i in one medium and the angle of reflection r in the other medium are measured with respect to the normal drawn to the surface at the point of incidence of light. Law of refraction is called Snell’s law

49. For normal incidence of light on a surface, the angle of incidence is______

1. 45⁰
2. 0⁰
3. 30⁰
4. 60⁰

Explanation

50. Which of the following is correct regarding Snell’s law?

1. Sin i / Sin r = n2/ n1
2. Sin i / Sin r = n1/ n2
3. Sin r / Sin i = n2/ n1
4. Sin r / Sin r₁ = n2/ n1

Explanation

The ratio of angle of incident i in the first medium to the angle of reflection r in the second medium is equal to the ratio of refractive index of the second medium n₂ to that of the refractive index of the first medium n₁.

51. The angle of deviation is equal to__, When light travels from rarer to denser medium

1. i – r
2. i + r
3. r – i
4. -i

Explanation

We know that the angle between the incident and deviated light is called angle of deviation. When light travels from rarer to denser medium it deviates towards normal as shown in Figure 6.16. The angle of deviation in this case is,

d = i – r

52. Which of the following statement about Characteristics of refraction is correct?

1. When light passes from rarer medium to denser medium it deviates towards normal in the denser medium.
2. When light passes from denser medium to rarer medium it deviates away from normal in the rarer medium
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Characteristics of refraction:

When light passes from rarer medium to denser medium it deviates towards normal in the denser medium.

When light passes from denser medium to rarer medium it deviates away from normal in the rarer medium.

53. The phenomenon in which a part of light from a source undergoing reflection and the other part of light from the same source undergoing refraction at the same surface is called____

1. Simultaneous refraction
2. Simultaneous refraction
3. Simultaneous dispersion
4. Either a or b

Explanation

The phenomenon in which a part of light from a source undergoing reflection and the other part of light from the same source undergoing refraction at the same surface is called simultaneous reflection or simultaneous refraction. Such surfaces are available as partially silvered glasses.\

54. Assertion(A): Production of optical surfaces capable of refracting as well as reflecting is possible

Reason(R): Glass can be made partially see through and partially reflecting by varying the amount of coating on its surface

1. Both (A) and (R) are correct, but (R) does not explain (A)
2. Both (A) and (R) are wrong
3. Both (A) and (R) are correct and (R) explains (A)
4. (A)is Correct and (R) is wrong

Explanation

Production of optical surfaces capable of refracting as well as reflecting is possible by properly coating the surfaces with suitable materials. Thus, a glass can be made partially see through and partially reflecting by varying the amount of coating on its surface.

55. Which of the following are the name of partially reflecting mirror?

1. Two-way mirror
2. Half-silvered mirror
3. Semi-silvered mirror
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Partially reflecting mirror is commercially called as two-way mirror, half-silvered or semi-silvered mirror etc.

56. Which of the following statement is correct?

1. In semi-silvered mirror, hidden cameras can be kept behind
2. We need to be cautious when we stand in front of mirrors kept in unknown places.
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Partially reflecting mirror is commercially called as two-way mirror, half- silvered or semi-silvered mirror etc. This gives a perception of regular mirror if the other side is made dark. But still hidden cameras can be kept behind such mirrors. We need to be cautious when we stand in front of mirrors kept in unknown places.

57. Which of the following statement about partially reflecting mirror is correct?

1. There is a method to test the two-way mirror
2. Place the finger nail against the mirror surface, if there is a gap between nail and its image, then it is a regular mirror.
3. If the fingernail directly touches its image, then it is a two-way mirror.
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

We need to be cautious when we stand in front of mirrors kept in unknown places. There is a method to test the two-way mirror. Place the finger nail against the mirror surface. If there is a gap between nail and its image, then it is a regular mirror. If the fingernail directly touches its image, then it is a two-way mirror.

58. Light travelling through transparent oil enters in to glass of refractive index 1.5. If the refractive index of glass with respect to the oil is 1.25, what is the refractive index of the oil?

1. 1.2
2. 2.5
3. 2.6
4. 1.7

Explanation

59. A coin is at the bottom of a trough containing three immiscible liquids of refractive indices 1.3, 1.4 and 1.5 poured one above the other of heights 30 cm, 16 cm, and 20 cm respectively. What is the apparent depth at which the coin appears to be when seen from air medium outside?

1. 47.8 cm
2. 33.8 cm
3. 27.8 cm
4. 77.8 cm

Explanation

60. When a ray passes from an optically denser medium to an optically rarer medium, it bends__ from Normal

1. Towards
2. Away
3. Into
4. None

Explanation

When a ray passes from an optically denser medium to an optically rarer medium, it bends away from normal. Because of this, the angle of refraction r on the rarer medium is greater than the corresponding angle of incidence i in the denser medium. As angle of incidence i is gradually increased, r rapidly increases and at a certain stage it becomes 90° or gracing the boundary.

61. Which of the following statement is correct?

1. Due to refraction of light through different layers of atmosphere which vary in refractive index, the path of light deviates continuously when it passes through atmosphere
2. Sun is visible a little before the actual sunrise and also until a little after the actual sunset due to refraction of light through the atmosphere
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Due to refraction of light through different layers of atmosphere which vary in refractive index, the path of light deviates continuously when it passes through atmosphere. For example, the Sun is visible a little before the actual sunrise and also until a little after the actual sunset due to refraction of light through the atmosphere. By actual sunrise what we mean is the actual crossing of the sun at the horizon

62. The apparent shift in the direction of the sun is around half a degree and the corresponding time difference between actual and apparent positions is about___

1. 4 minutes
2. 2 minutes
3. 3 minutes
4. 10 minutes

Explanation

The apparent shift in the direction of the sun is around half a degree and the corresponding time difference between actual and apparent positions is about 2 minutes. Sun appears flattened (oval shaped) during sun rise and sunset due to the same phenomenon.

63. Which of the following statement is correct?

1. If the angle of incidence in the denser medium is increased beyond the critical angle, there is no refraction possible in to the rarer medium
2. The entire light is reflected back into the denser medium itself. This phenomenon is called total internal reflection
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

If the angle of incidence in the denser medium is increased beyond the critical angle, there is no refraction possible in to the rarer medium. The entire light is reflected back into the denser medium itself. This phenomenon is called total internal reflection.

64. Which of the following are the conditions for total internal reflection?

1. Light must travel from denser to rarer medium
2. Angle of incidence in the denser medium must be greater than critical angle
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

The two conditions for total internal reflection are,

(a) light must travel from denser to rarer medium,

(b) angle of incidence in the denser medium must be greater than critical angle (i>i_c).

65. The critical angle for water-air interface is____^o

1. 45
2. 48.6
3. 34.5
4. 12.5

Explanation

Refractive index of glass is about 1.5. The critical angle for glass-air interface is

The critical angle for water-air interface is,

66. Match the refractive index with the respective material:

A.Ice 1. 1.541

B.Water 2. 1.333

C.Crown glass 3. 1.310

D.Diamond 4. 2.417

1. 2, 1, 3, 4
2. 3, 2, 1, 4
3. 2, 3, 1, 4
4. 4, 1, 2, 3

Explanation

67. Which of the followign statement is correct?

1. Diamond appears dazzling because the total internal reflection of light happens inside the diamond
2. The refractive index of only diamond is about 1.417.
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Diamond appears dazzling because the total internal reflection of light happens inside the diamond. The refractive index of only diamond is about 2.417.

68. The critical angle of diamond is about____ ^o

1. 34.4
2. 24.4
3. 14.4
4. 49.9

Explanation

Diamond is much larger than that for ordinary glass which is about only 1.5. The critical angle of diamond is about 24.4°. It is much less than that of glass. A skilled diamond cutter makes use of this larger range of angle of incidence (24.4° to 90° inside the diamond), to ensure that light entering the diamond is total internally reflected from the many cut faces before getting out.

69. Which of the following statement is correct?

1. The refractive index of air increases with its density
2. Hot air is more dense
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

The refractive index of air increases with its density. In hot places, air near the ground is hotter than air at a height. Hot air is less dense.

70 . Assertion(A): In the cold places the refractive index increases towards the ground

Reason(R): The temperature of air close to the ground is lesser than the temperature above the surface of earth

1. Both (A) and (R) are correct, but (R) does not explain (A)
2. Both (A) and (R) are wrong
3. Both (A) and (R) are correct and (R) explains (A)
4. (A)is Correct and (R) is wrong

Explanation

In the cold places the refractive index increases towards the ground because the temperature of air close to the ground is lesser than the temperature above the surface of earth. Thus, the density and refractive index of air near the ground is greater than at a height.

71. Where does reverse effect of mirage will take place?

1. Desert
2. Glacier
3. Sea
4. Frozen lake
5. 1, 2, 4
6. 1, 3, 4
7. 2, 3, 4
8. All the above

Explanation

In the cold regions like glaciers and frozen lakes and seas, the reverse effect of mirage will happen. Hence, an inverted image is formed little above the surface.

72. Which of the following statement is correct?

1. When a light source like electric bulb is kept inside a water tank, the light from the source travels in all direction inside the water
2. The light that is incident on the water surface at an angle less than the critical angle will undergo refraction and emerge out from the water.
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

When a light source like electric bulb is kept inside a water tank, the light from the source travels in all direction inside the water. The light that is incident on the water surface at an angle less than the critical angle will undergo refraction and emerge out from the water. The light incident at an angle greater than critical angle will undergo total internal reflection.The light falling particularly at critical angle graces the surface.

73. What is the radius of the illumination when seen above from inside a swimming pool from a depth of 10 m on a sunny day? What is the total angle of view? [Given, refractive index of water is 4/3]

1. 48.6^o
2. 97.2^o
3. 112.9^o
4. 99.2^o

Explanation

74. Which of the following statement is correct?

1. Transmitting signals through optical fibres is possible due to the phenomenon of total internal reflection.
2. Optical fibres consists of inner part called core and outer part called cladding (or) sleeving.
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Transmitting signals through optical fibres is possible due to the phenomenon of total internal reflection. Optical fibres consists of inner part called core and outer part called cladding (or) sleeving

75. The refractive index of the material of the core must be___ than that of the cladding for total internal reflection to happen

1. Lower
2. Higher
3. Equal to
4. None

Explanation

The refractive index of the material of the core must be higher than that of the cladding for total internal reflection to happen. Signal in the form of light is made to incident inside the core-cladding boundary at an angle greater than the critical angle. Hence, it undergoes repeated total internal reflections along the length of the fibre without undergoing any refraction.

76. Which of the following statement is incorrect?

1. To ensure the critical angle incidence in the core-cladding boundary inside the optical fibre, the light should be incident at a certain angle at the end of the optical fiber while entering in to it
2. This angle is called acceptance angle.
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

To ensure the critical angle incidence in the core-cladding boundary inside the optical fibre, the light should be incident at a certain angle at the end of the optical fiber while entering in to it. This angle is called acceptance angle

77. Which of the following statement is correct?

1. An endoscope is an instrument used by doctors which has a bundle of optical fibres that are used to see inside a patient’s body.
2. Endoscopes work on the phenomenon of total internal refraction
3. Even operations could be carried out with the endoscope cable which has the necessary instruments attached at their ends.
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

An endoscope is an instrument used by doctors which has a bundle of optical fibres that are used to see inside a patient’s body. Endoscopes work on the phenomenon of total internal reflection. The optical fibres are inserted in to the body through mouth, nose or a special hole made in the body. Even operations could be carried out with the endoscope cable which has the necessary instruments attached at their ends.

78. The thickness of a glass slab is 0.25 m. it has a refractive index of 1.5. A ray of light is incident on the surface of the slab at an angle of 60^o. Find the lateral displacement of the light when it emerges from the other side of the mirror(in cm).

1. 12.81
2. 14.21
3. 16.21
4. 32.81

Explanation

79. Which of the following statement is correct?

1. The refractions also do take place at spherical surface between two transparent media
2. The laws of refraction hold good at every point on the spherical surface.
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

The refractions also do take place at spherical surface between two transparent media. The laws of refraction hold good at every point on the spherical surface. The normal at the point of incidence is perpendicular to the tangent plane to the spherical surface at that point.

80. Which of the following assumptions are made while considering refraction at spherical surfaces?

1. The incident light is assumed to be dichromatic
2. The incident light is assumed to be monochromatic
3. The incident ray of light is very close to the principal axis
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

The following assumptions are made while considering refraction at spherical surfaces.

The incident light is assumed to be monochromatic (single colour)

The incident ray of light is very close to the principal axis (paraxial rays).

81. Locate the image of the point object O in the situation shown. The point C denotes the centre of curvature of the separating surface.

a)Virutal image

b)Real image

c)Either a or b

d)Both a and b

Explanation

82. Find the size of the image formed in the given figure.

a)6 cm

b)0.6 cm

c)0.8 cm

d)2.1 cm

Explanation

83. Which of the following statement is correct?

1. A lens is formed by a transparent material bounded between two spherical surfaces or one plane and another spherical surface
2. In a thin lens, the distance between the surfaces is very small.
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

A lens is formed by a transparent material bounded between two spherical surfaces or one plane and another spherical surface. In a thin lens, the distance between the surfaces is very small. If there are two spherical surfaces, then there will be two centres of curvature C₁ and C₂ and correspondingly two radii of curvature R₁ and R₂.

84. Which of the following statement is correct?

1. The primary focus F1 is defined as a point where an object should be placed to give parallel emergent rays to the principal axis
2. The secondary focus F2 is defined as a point where all the parallel rays travelling close to the principal axis converge to form an image on the principal axis
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

The primary focus F1 is defined as a point where an object should be placed to give parallel emergent rays to the principal axis. For a convergent lens, such an object is a real object and for a divergent lens, it is a virtual object. The distance PF1 is the primary focal length f1 . The secondary focus F2 is defined as a point where all the parallel rays travelling close to the principal axis converge to form an image on the principal axis. For a convergent lens, such an image is a real image and for a divergent lens, it is a virtual image. The distance PF2 is the secondary focal length f 2.

85. The focal length of the thin lens is taken as___ for a converging lens and___ for a diverging lens.

1. +, –
2. -, –
3. +, +
4. -, +

Explanation

The sign of focal length is not decided on the direction of measurement of the focal length from the pole of the lens as they have two focal lengths, one to the left and another to the right (primary and secondary focal lengths on either side of the lens). The focal length of the thin lens is taken as positive for a converging lens and negative for a diverging lens.

86. Which of the following is lens equation?

1. 1/f = 1/u -1/v
2. 1/f = 1/v – 1/u
3. 1/f = 1/u + 1/v
4. 1/f = -1/u + 1/v

Explanation

This equation is known as lens equation which relates the object distance u and image distance v with the focal length f of the lens. This formula holds good for a any type of lens

87. A biconvex lens has radii of curvature 20 cm and 15 cm each. The refractive index of the material of the lens is 1.5. What is its focal length?(cm)

1. 17.14
2. 14.17
3. 23.18
4. 12.12

Explanation

88. Determine the focal length of the lens made up of a material of refractive index 1.52 as shown in the diagram. (Points C1 and C2 are the centers of curvature of the first and second surface.)

1. 38. 46 cm
2. 39.46 cm
3. 42.12 cm
4. 19.18 cm

Explanation

89. Which of the following statement is correct?

1. Power of lens is the measurement of deviating strength of a lens
2. Power of the lens is directly proportional to focal length
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Power of lens is the measurement of deviating strength of a lens i.e. when a ray is incident on a lens then the degree with which the lens deviates the ray is determined by the power of the lens. Power of the lens is inversely proportional to focal length i.e. greater the power of lens, greater will be the deviation of ray and smaller will be the focal length.

90. If the focal length is 150 cm for a glass lens, what is the power of the lens?(in D)

1. 0.67
2. 0.91
3. 0.33
4. 0.71

Explanation

91. What is the focal length of the combination if a lens of focal length –70 cm is brought in contact with a lens of focal length 150 cm?

1. 131.25 cm
2. -131.25 cm
3. 121.25 cm
4. -121.25 cm

Explanation

Given, focal length of first lens, f₁ = –70 cm, focal length of second lens, f ₂ = 150 cm.

92. What is the focal length of the combination if a lens of focal length –70 cm is brought in contact with a lens of focal length 150 cm? What is the power of the combination?

a)– 0.67 D

b)– 0.76 D

c)0.67 D

d)0.76 D

Explanation

Given, focal length of first lens, f₁ = –70 cm, focal length of second lens, f ₂ = 150 cm.

93. System of combination of lenses is commonly used in designing lenses for____

1. Camera
2. Microscope
3. Telescopes
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

System of combination of lenses is commonly used in designing lenses for cameras, microscopes, telescopes and other optical instruments. They produce better magnification as well as sharpness of the images.

94. Which of the following statement is correct?

1. A prism is a triangular block of glass or plastic
2. It is bounded by the three plane faces not parallel to each other.
3. Its one face is grounded which is called base of the prism.
4. The other two faces are polished which are called refracting faces of the prism
5. 1, 2, 3
6. 2, 3, 4
7. 1, 3, 4
8. All the above

Explanation

A prism is a triangular block of glass or plastic. It is bounded by the three plane faces not parallel to each other. Its one face is grounded which is called base of the prism. The other two faces are polished which are called refracting faces of the prism. The angle between the two refracting faces is called angle of prism (or) refracting angle (or) apex angle of the prism.

95. Angle of deviation depends on Which of the following factors?

1. Angle of incidence
2. Angle of the prism
3. Material of the prism
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

The angle of deviation depends on these following factors:

(i) the angle of incidence

(ii) the angle of the prism

(iii) the material of the prism

(iv) the wave length of the light

96. A monochromatic light is incident on an equilateral prism at an angle 30^o and emerges at an angle of 75^o . What is the angle of deviation produced by the prism?

1. 30^o
2. 45^o
3. 90^o
4. 60^o

Explanation

97. Light ray falls at normal incidence on the first face of an equilateral prism and emerges gracing the second face. What is the angle of deviation?

1. 45^o
2. 30^o
3. 60^o
4. 90^o

Explanation

98. Light ray falls at normal incidence on the first face of an equilateral prism and emerges gracing the second face. What is the refractive index of the material of the prism?

1. 4
2. 3
3. 2
4. 7

Explanation

99. The angle of minimum deviation for a prism is 37o . If the angle of prism is 60o , find the refractive index of the material of the prism.

1. 2
2. 3.5
3. 1.5
4. 4.5

Explanation

100. Which of the following statement is correct?

1. When white light enter in to a prism, the effect called dispersion takes place.
2. Dispersion is splitting of white light into its constituent colours.
3. This band of colours of light is called its spectrum.
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

So far the angle of deviation produced by a prism is discussed for monochromatic light (i.e. light of single colour). When white light enter in to a prism, the effect called dispersion takes place. Dispersion is splitting of white light into its constituent colours. This band of colours of light is called its spectrum.

101. Which of the following colour is most deviated?

1. Red
2. Orange
3. Violet
4. Green

Explanation

When a narrow beam of parallel rays of white light is incident on the face of a prism and the refracted beam is received on a white screen, a band of colours is obtained in the order, recollected by the word: VIBGYOR i.e., Violet, Indigo, Blue, Green, Yellow, Orange and Red. Violet is the most deviated and red is the least deviated colour.

102. Which of the following statement is correct?

1. The colours obtained in a spectrum depend on the nature of the source of the light used
2. Each colour of light is associated with a definite wavelength
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

The colours obtained in a spectrum depend on the nature of the source of the light used. Each colour of light is associated with a definite wavelength.

103. What is the wavelength of violet light?

1. 400 nm
2. 700 nm
3. 200 nm
4. 1300 nm

Explanation

Red light is at the longer wavelength end (700 nm) while the violet light is at the shorter wavelength end (400 nm). Therefore the violet ray travels with a smaller velocity in glass prism than red ray.

104. _____ has demonstrated through a classic experiment to produce white light when all the colours of VIBGYOR are recombined

1. Einstein
2. Newton
3. Galileo
4. Edison

Explanation

Sir Isaac Newton has demonstrated through a classic experiment to produce white light when all the colours of VIBGYOR are recombined. He used a prism to produce dispersion and made all the colours to incident on another inverted prism to combine all the colours to get white light.

105. Which of the following statement is correct?

1. Dispersion takes place because light of different wave lengths travel with different speeds inside the prism
2. In Vacuum, all the colours travel with the same speed
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Dispersion takes place because light of different wave lengths travel with different speeds inside the prism. . In Vacuum, all the colours travel with the same speed. The refractive index of two different glasses for different colours.

106. Which light has high refractive index?

1. Red
2. Violet
3. Blue
4. Orange

Explanation

In other words, the refractive index of the material of the prism is different for different colours. For violet, the refractive index is high and for red the refractive index is the low.

107. Which of the following statement is correct?

1. The speed of light is independent of wavelength in vacuum
2. vacuum is a non-dispersive medium in which all colours travel with the same speed
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

The speed of light is independent of wavelength in vacuum. Therefore, vacuum is a non-dispersive medium in which all colours travel with the same speed.

108. Match the following colour of light with their wavelength(nm)

A.Violet 1. 656.3

B.Blue 2. 589.3

C.Yellow 3. 486.1

D.Red 4. 396.6

1. 1, 3, 2, 4
2. 4, 2, 3, 1
3. 4, 3, 2, 1
4. 1, 4, 2, 3

Explanation

109. Find the dispersive power of flint glass if the refractive indices of flint glass for red, green and violet light are 1.613, 1.620 and 1.632 respectively.

1. 0.0306
2. 0.0405
3. 0.0333
4. 0.0230

Explanation

110. Which of the following statement is correct?

1. When sunlight enters the atmosphere of the earth, the atmospheric particles present in the atmosphere change the direction of the light
2. This process is known as dispersion of light.
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

When sunlight enters the atmosphere of the earth, the atmospheric particles present in the atmosphere change the direction of the light. This process is known as scattering of light.

111. The intensity of Rayleigh’s scattering is inversely proportional to_____ power of wavelength

1. 3^rd
2. 4^th
3. 5^th
4. 6^th

Explanation

If the scattering of light is by atoms and molecules which have size a very less than that of the wave length λ of light a<< λ, scattering is called Rayleigh’s scattering. The intensity of Rayleigh’s scattering is inversely proportional to fourth power of wavelength.

112. Which of the following statement is correct?

1. Violet colour which has the shortest wavelength gets much scattered during day time
2. Blue light which has shorter wavelength is scattered away and the less-scattered red light of longer wavelength
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

According to equation, violet colour which has the shortest wavelength gets much scattered during day time. The next scattered colour is blue. As our eyes are more sensitive to blue colour than violet colour the sky appears blue during day time. But, during sunrise and sunset, the light from sun travels a greater distance through the atmosphere. Hence, the blue light which has shorter wavelength is scattered away and the less-scattered red light of longer wavelength manages to reach our eye.

113. The angle of view for violet to red in primary rainbow is___^o to____ ^o

1. 52, 54
2. 40, 42
3. 54, 65
4. 32, 56

Explanation

Primary rainbow is formed when light entering the drop undergoes one total internal reflection inside the drop before coming out from the drop as shown in figure. The angle of view for violet to red in primary rainbow is 40^o to 42^o.

114. The angle of view for red to violet in a secondary rainbow is,____^o to___ ^o

1. 52, 54
2. 40, 42
3. 54, 65
4. 32, 56

Explanation

A secondary rainbow appears outside of a primary rainbow and develops when light entering a raindrop undergoes two internal reflections. The angle of view for red to violet in a secondary rainbow is, 52^o to 54^o.

115. Which of the following statement is correct?

1. Rainbow is an example of dispersion of sunlight through droplets of water during rainy days.
2. When sunlight falls on the water drop suspended in air, it splits (or dispersed) into its constituent six colours
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Rainbow is an example of dispersion of sunlight through droplets of water during rainy days. Rainbow is observed during a rainfall or after the rainfall or when we look at a water fountain provided the sun is at the back of the observer. When sunlight falls on the water drop suspended in air, it splits (or dispersed) into its constituent seven colours.

116. Assertion(A): If earth has no atmosphere the sky would be dark

Reason(R): If earth has no atmosphere there would not have been any scattering

1. Both (A) and (R) are correct, but (R) does not explain (A)
2. Both (A) and (R) are wrong
3. Both (A) and (R) are correct and (R) explains (A)
4. (A) is Correct and (R) is wrong

Explanation

If earth has no atmosphere there would not have been any scattering and the sky would appear dark. That is why sky appears dark for the astronauts who could see the sky from above the atmosphere.

117. Which of the following statement is correct?

1. In clouds all the colours get equally scattered irrespective of wavelength
2. Rain clouds appear dark because of the condensation of water droplets on dust particles that makes the cloud become opaque
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

In clouds all the colours get equally scattered irrespective of wavelength. This is the reason for the whitish appearance of cloud as shown. But, the rain clouds appear dark because of the condensation of water droplets on dust particles that makes the cloud become opaque.

118. Which of the following statement is correct?

1. Light is a form of energy that is transferred from one place to another
2. A glance at the evolution of various theories of light put forward by scientists will give not only an over view of the nature of light but also its propagation and some phenomenon demonstrated by it
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Light is a form of energy that is transferred from one place to another. A glance at the evolution of various theories of light put forward by scientists will give not only an over view of the nature of light but also its propagation and some phenomenon demonstrated by it.

119. Who among the following gave Corpuscular theory?

1. Newton
2. Einstein
3. Edison
4. Galileo

Explanation

Sir Isaac Newton (1672) gave the corpuscular theory of light which was also suggested earlier by Descartes (1637) to explain the laws of reflection and refraction.

120. Which of the following statement is correct?

1. According Corpusculartheory, light is emitted as tiny, massless (negligibly small mass) and perfectly elastic particles called corpuscles
2. As the corpuscles are very small, the source of light does not suffer appreciable loss of mass even if it emits light for a long time
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

According this theory, light is emitted as tiny, massless (negligibly small mass) and perfectly elastic particles called corpuscles. As the corpuscles are very small, the source of light does not suffer appreciable loss of mass even if it emits light for a long time. On account of high speed, they are unaffected by the force of gravity and their path is a straight line in a medium of uniform refractive index.

121. The energy of light is the____ energy of corpuscles

1. Potential
2. Kinetic
3. Either a or b
4. Both a and b

Explanation

On account of high speed, they are unaffected by the force of gravity and their path is a straight line in a medium of uniform refractive index. The energy of light is the kinetic energy of these corpuscles. When these corpuscles impinge on the retina of the eye, the vision is produced.

122. Which of the following phenomena cannot be explained by corpuscular theory?

1. Polarisation
2. Interference
3. Diffraction
4. All the above

Explanation

Corpuscular theory could not explain the reason why the speed of light is lesser in denser medium than in rarer medium and also the phenomena like interference, diffraction and polarisation.

12th Science Lesson 10 Questions in English

10] Electronics and Communication

1. Which of the following statement is correct?

1. The communication industry is one of the largest in size and is the oldest
2. Right from the developments made in communication by great scientists like J.C. Bose, G. Marconi, and Alexander Graham Bell, communication has witnessed leaps and bounds
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Communication exists since the dawn of life in this world. Growth in science and technology removed the locational disadvantage effectively. Information can be exchanged from one person to another anywhere on this Earth. Right from the developments made in communication by great scientists like J.C. Bose, G. Marconi, and Alexander Graham Bell, communication has witnessed leaps and bounds. The communication industry is one of the largest in size and is the oldest since communication through telegraph (1844), telephone (1876), and Radio (1887) started centuries back.

2. Which century witnessed a leap over the development of communication?

1. 18^th
2. 19^th
3. 20^th
4. 21^st

Explanation

The intensive research in the mid- and late nineteenth century leads to the development of long-distance transmission in the shortest possible time. However, the 20th century witnessed a leap over the development of communication, meeting the demands of speed and secured transfer of data.

3. Which of the following is audio frequency?

1. 20 to 20000 Hz
2. 20 to 20000 MHz
3. 10 to 10000 Hz
4. 10 to 10000 MHz

Explanation

The transmission of information through short distances does not require complicated techniques. The energy of the information signal is sufficient enough to be sent directly. However, if the information, for example, audio frequency (20 to 20,000 Hz) needs to be transmitted to long distances across the world, certain techniques are required to transmit the information without any loss.

4. Carrier signal is a________

1. Low frequency signal
2. High frequency signal
3. Very High frequency signal
4. Medium frequency signal

Explanation

For long distance transmission, the low frequency baseband signal (input signal) is superimposed onto a high frequency radio signal by a process called modulation. In the modulation process, a very high frequency signal called carrier signal (radio signal) is used to carry the baseband signal.

5. The carrier signal is usually a______ wave

1. Sine
2. Cosine
3. Tan
4. Cot

Explanation

The carrier signal is usually a sine wave signal. In the modulation process, a very high frequency signal called carrier signal (radio signal) is used to carry the baseband signal.

6. Which of the following statement is correct?

1. As the frequency of the carrier signal is very high, it can be transmitted to long distances with less attenuation.
2. Carrier signal does not have information.
3. The carrier signal will be more compatible with the communication medium like free space and can propagate with greater efficiency.
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

As the frequency of the carrier signal is very high, it can be transmitted to long distances with less attenuation. The carrier signal is usually a sine wave signal. Also, the carrier signal will be more compatible with the communication medium like free space and can propagate with greater efficiency. Carrier signal does not have information.

7. e_c = E_c sin (2πν_c t + ϕ), What does E_c mean?

1. Frequency
2. Amplitude
3. Initial energy
4. Frequency modulated

Explanation

A sinusoidal carrier wave can be represented as e_c = E_c sin (2πν_c t + ϕ), where Ec is the amplitude, νc is the frequency and ϕ is the initial phase of the carrier wave at any instant of time t.

8. Which of the following parameters of carrier signal can be modified?

1. Amplitude
2. Phase
3. Frequency
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Three characteristics in the carrier signal can be modified by the baseband signal during the process of modulation: amplitude, frequency and phase of the carrier signal.

9. How many types of many types of modulation are there based on modification parameters?

1. 3
2. 5
3. 4
4. 5

Explanation

There are 3 types of modulation based on which parameter is modified. They are (i) amplitude modulation, (ii) frequency modulation and (iii) phase modulation.

10. Which of the following statement is correct?

1. If the amplitude of the carrier signal is modified in proportion to the instantaneous amplitude of the baseband signal, then it is called amplitude modulation
2. Here the frequency and the phase of the carrier signal remain constant
3. Amplitude modulation is used in radio, mobile and TV broadcasting
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

If the amplitude of the carrier signal is modified in proportion to the instantaneous amplitude of the baseband signal, then it is called amplitude modulation. Here the frequency and the phase of the carrier signal remain constant. Amplitude modulation is used in radio and TV broadcasting.

11. Which of the following are advantage of AM?

1. Low cost
2. Low noise
3. High operating range
4. High efficiency

Explanation

Advantages of AM

i) Easy transmission and reception

ii) Lesser bandwidth requirements

iii) Low cost

12. Which of the following statement is correct about Frequency modulation?

1. The frequency of the baseband signal is modified in proportion to the instantaneous amplitude of the carrier signal
2. Increase in the amplitude of the baseband signal increases the frequency of the carrier signal and vice versa
3. The amplitude and the phase of the carrier signal remain constant.
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

The frequency of the carrier signal is modified in proportion to the instantaneous amplitude of the baseband signal in frequency modulation. Here the amplitude and the phase of the carrier signal remain constant. Increase in the amplitude of the baseband signal increases the frequency of the carrier signal and vice versa.

13. Louder signal leads to______ and relatively weaker signals to____

1. Rarefactions, Compression
2. Compression, Rarefaction
3. Compression, Compression
4. Rarefaction, compression

Explanation

Increase in the amplitude of the baseband signal increases the frequency of the carrier signal and vice versa. This leads to compressions and rarefactions in the frequency spectrum of the modulated wave. Louder signal leads to compressions and relatively weaker signals to rarefactions.

14. Which of the following statement is correct?

1. When the frequency of the baseband signal is zero (no input signal), there is no change in the frequency of the carrier wave
2. It is at its normal frequency and is called as centre frequency or resting frequency
3. Practically this is the allotted frequency of the FM transmitter
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

When the frequency of the baseband signal is zero (no input signal), there is no change in the frequency of the carrier wave. It is at its normal frequency and is called as centre frequency or resting frequency. Practically this is the allotted frequency of the FM transmitter.

15. Which of the following are advantages of FM?

1. Decreased signal to noise ratio
2. FM bandwidth covers the entire frequency range which humans can hear
3. The operating range is quite large
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Advantages of FM

i) Large decrease in noise. This leads to an increase in signal-noise ratio.

ii) The operating range is quite large.

iii) The transmission efficiency is very high as all the transmitted power is useful.

iv) FM bandwidth covers the entire frequency range which humans can hear. Due to this, FM radio has better quality compared to AM radio.

16. Which of the following statement is correct?

1. In phase modulation, the instantaneous amplitude of the baseband signal modifies the phase of the carrier signal keeping the amplitude and frequency constant
2. This modulation is used to generate frequency modulated signals
3. It is similar to frequency modulation except that the phase of the carrier is varied instead of varying frequency
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

In phase modulation, the instantaneous amplitude of the baseband signal modifies the phase of the carrier signal keeping the amplitude and frequency constant. This modulation is used to generate frequency modulated signals. It is similar to frequency modulation except that the phase of the carrier is varied instead of varying frequency.

17. Which of the following statement is correct?

1. If a square wave is used as the baseband signal, then phase reversal takes place in the modulated signal
2. FM and PM waves are same as square wave modulating signal
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

If a square wave is used as the baseband signal, then phase reversal takes place in the modulated signal. FM and PM waves are completely different for square wave modulating signal.

18. The frequency shift in phase modulation depends on____

1. Amplitude of the carrier signal
2. Amplitude of the modulating signal
3. The frequency of the signal
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

The frequency shift in carrier wave frequency exists in phase modulation as well. The frequency shift depends on (i) amplitude of the modulating signal and (ii) the frequency of the signal.

19. Which of the following statement is correct?

1. PM wave is similar to FM wave
2. PM generally uses a larger bandwidth than FM
3. Phase modulation provides high transmission speed on a given bandwidth
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

PM wave is similar to FM wave. PM generally uses a smaller bandwidth than FM. In other words, in PM, more information can be sent in a given bandwidth. Hence, phase modulation provides high transmission speed on a given bandwidth.

20. Which of the following statement is correct?

1. Electronics plays a major role in communication
2. Electronic communication is nothing but the transmission of sound, text, pictures, or data through a medium
3. Long distance transmission uses free space as a medium
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Electronics plays a major role in communication. Electronic communication is nothing but the transmission of sound, text, pictures, or data through a medium. Long distance transmission uses free space as a medium. This section provides sufficient information on how voice signal is transmitted by a transmitter through space and received by the receiver at the receiving end.

21. Which of the following could be input to the input transducer?

1. Image
2. Music
3. Speech
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Information can be in the form of speech, music, pictures, or computer data. This information is given as input to the input transducer.

22. ____ is a device that converts variations in a physical quantity into an equivalent electrical signal or vice versa

1. Transmitter
2. Receiver
3. Transducer
4. Oscillator

Explanation

A transducer is a device that converts variations in a physical quantity (pressure, temperature, sound) into an equivalent electrical signal or vice versa.

23. The electrical equivalent of the original information is called________

1. Broadband signal
2. Baseband signal
3. Carrier signal
4. All the above

Explanation

The electrical equivalent of the original information is called the baseband signal. The best example for the transducer is the microphone that converts sound energy into electrical energy

24. Which of the following circuits are included in transmitter?

1. Amplifier
2. Modulator
3. Power amplifier
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Transmitter feeds the electrical signal from the transducer to the communication channel. It consists of circuits such as amplifier, oscillator, modulator and power amplifier. The transmitter is located at the broadcasting station.

25. Which of the following statement is correct?

1. The transducer output is very weak and is amplified by the amplifier.
2. Oscillator generates high-frequency carrier wave (a sinusoidal wave) for long distance transmission into space.
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Amplifier: The transducer output is very weak and is amplified by the amplifier.

Oscillator: It generates high-frequency carrier wave (a sinusoidal wave) for long distance transmission into space. As the energy of a wave is proportional to its frequency, the carrier wave has very high energy.

26. _________ superimposes the baseband signal onto the carrier signal.

1. Oscillator
2. Amplifier
3. Modulator
4. Power amplifier

Explanation

Modulator superimposes the baseband signal onto the carrier signal and generates the modulated signal.

27. What is the velocity of Electromagnetic waves?

1. 3 × 10⁸ m s^–1
2. 3 × 10⁸ m s
3. 3 × 10⁹ m s^–1
4. 3 × 10⁸ m s^–2

Explanation

Transmitting antenna radiates the radio signal into space in all directions. It travels in the form of electromagnetic waves with the velocity of light (3 × 10⁸ m s^–1)

28. Which of the following statement is correct?

1. Communication channel is used to carry the electrical signal from transmitter to receiver with less noise or distortion
2. The communication medium is basically of two types: wireline communication and wireless communication
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Communication channel is used to carry the electrical signal from transmitter to receiver with less noise or distortion. The communication medium is basically of two types: wireline communication and wireless communication.

29. Which of the following are used in wireline connection?

1. Cable
2. Wires
3. Optic fibers
4. All the above

Explanation

Wireline communication (point to point communication) uses mediums like wires, cables and optical fibres. These systems cannot be used for long distance transmission as they are connected physically. Examples are telephone, intercom and cable TV.

30. Which of the following statement is correct?

1. Wireless communication uses free space as a communication medium
2. The signals are transmitted in the form of electromagnetic waves with the help of a transmitting antenna
3. Mobile, radio or TV broadcasting and satellite communication are examples of wireless communication
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Wireless communication uses free space as a communication medium. The signals are transmitted in the form of electromagnetic waves with the help of a transmitting antenna. Hence wireless communication is used for long distance transmission. Examples are mobile, radio or TV broadcasting and satellite communication.

31. Which of the following statement about noise is correct?

1. It is the undesirable electrical signal that interferes with the transmitted signal.
2. Noise can be completely eliminated
3. Noise attenuates or reduces the quality of the transmitted signal.
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Noise is the undesirable electrical signal that interferes with the transmitted signal. Noise attenuates or reduces the quality of the transmitted signal. Noise cannot be completely eliminated. However, it can be reduced using various techniques.

32. Which of the following are man-made noise disturbance?

1. Radiation from Sun
2. Automobiles
3. Electric motor
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Noise may be man-made (automobiles, welding machines, electric motors etc.) or natural (lightning, radiation from sun and stars and environmental effects).

33. Which of the following statement is correct?

1. The signals that are transmitted through the communication medium are received by a receiving antenna which converts EM waves into RF signals and are fed into the receiver.
2. The receiver consists of electronic circuits like demodulator, amplifier, detector etc.
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

The signals that are transmitted through the communication medium are received by a receiving antenna which converts EM waves into RF signals and are fed into the receiver. The receiver consists of electronic circuits like demodulator, amplifier, detector etc. The demodulator extracts the baseband signal from the modulated signal. Then the baseband signal is detected and amplified using amplifiers. Finally, it is fed to the output transducer.

34. Which of the following statement is incorrect?

1. Repeaters are used to increase the range or distance through which the signals are sent
2. The signals are received, amplified and retransmitted with a carrier signal of different frequency to the destination
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Repeaters are used to increase the range or distance through which the signals are sent. It is a combination of transmitter and receiver. The signals are received, amplified and retransmitted with a carrier signal of different frequency to the destination. The best example is the communication satellite in space

35. Which of the following are output transducer?

1. Speakers
2. Picture tubes
3. Microphone
4. Computer monitor
5. 1, 2, 4
6. 1, 2, 3
7. 2, 3, 4
8. All the above

Explanation

Output transducer converts the electrical signal back to its original form such as sound, music, pictures or data. Examples of output transducers are loudspeakers, picture tubes, computer monitor, etc.

36. The loss of strength of a signal while propagating through a medium is known as_______

1. Reduction
2. Attenuation
3. Distraction
4. All the above

Explanation

The loss of strength of a signal while propagating through a medium is known as attenuation. Range is the maximum distance between the source and the destination up to which the signal is received with sufficient strength.

37. Which of the following can be transmitted through bandwidth of signal?

1. Voice
2. Music
3. Picture
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

The frequency range over which the baseband signals or the information signals such as voice, music, picture etc is transmitted is known as bandwidth. Each of these signals has different frequencies.

38. Bandwidth gives the difference between the____ and____ frequency limits of the signal

1. Upper, middle
2. Middle, lower
3. Upper, lower
4. Upper, upper

Explanation

The type of communication system depends on the nature of the frequency band for a given signal. Bandwidth gives the difference between the upper and lower frequency limits of the signal.

39. The height of the antenna must be a multiple of_____

1. λ/ 4
2. λ/ 2
3. λ/ 3
4. λ/ 5

Explanation

Antenna is used at both transmitter and receiver end. Antenna height is an important parameter to be discussed. The height of the antenna must be a multiple of h = λ/ 4

40. The frequencies from___ kHz to____ GHz are transmitted through wireless communication

1. 1, 100
2. 2, 200
3. 3, 300
4. 2, 400

Explanation

The information signal modulated with the carrier wave (radio wave) is transmitted by an antenna. This travels through space and is received by the receiving antenna at the other end. The frequencies from 2 kHz to 400 GHz are transmitted through wireless communication.

41. Match the following

A.Ground wave propagation 1. 30 MHz to 400 GHz

B.Sky wave propagation 2. 2 kHz to 2 MHz

C.Space wave propagation 3. 3 MHz to 30 MHz

1. 3, 1, 2
2. 2, 1, 3
3. 2, 3, 1
4. 1, 2, 3

Explanation

• Ground wave propagation (or) surface wave propagation (nearly 2 kHz to 2 MHz)

• Sky wave propagation (or) ionospheric propagation (nearly 3 MHz to 30 MHz)

• Space wave propagation (nearly 30 MHz to 400 GHz)

42. Which of the following statement is correct?

1. If the electromagnetic waves transmitted by the transmitter glide over the surface of the earth to reach the receiver, then the propagation is called ground wave propagation
2. Both transmitting and receiving antennas must be close to the earth
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

If the electromagnetic waves transmitted by the transmitter glide over the surface of the earth to reach the receiver, then the propagation is called ground wave propagation. The corresponding waves are called ground waves or surface waves. Both transmitting and receiving antennas must be close to the earth. The size of the antenna plays a major role in deciding the efficiency of the radiation of signals.

43. The attenuation of the signal with distance depends on_____

1. Frequency of the transmitter
2. Power of the transmitter
3. Condition of the earth surface
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

The attenuation of the signal with distance depends on (i) power of the transmitter (ii) frequency of the transmitter and (iii) condition of the Earth surface.

44. The earth behaves like a leaky_____

1. Insulator
2. Resistor
3. Capacitor
4. Inductor

Explanation

When the transmitted signal in the form of EM wave is in contact with the Earth, it induces charges in the Earth and constitutes a current. Due to this, the Earth behaves like a leaky capacitor which leads to the attenuation of the wave.

45. The frequency of the ground waves is mostly less than____ MHz

1. 10
2. 20
3. 2
4. 34

Explanation

The frequency of the ground waves is mostly less than 2 MHz as high frequency waves undergo more absorption of energy at the earth’s atmosphere.

46. Surface wave propagation is used in____

1. Ship to ship
2. Ship to shore
3. Mobile communication
4. All the above

Explanation

The medium wave signals received during the day time use surface wave propagation. It is mainly used in local broadcasting, radio navigation, for ship-to-ship, ship to-shore communication and mobile communication.

47. Which of the following statement is incorrect?

1. The mode of propagation in which the electromagnetic waves radiated from an antenna, directed upwards at large angles, gets reflected by the troposphere back to earth is called ionospheric propagation
2. The corresponding waves are called sky waves
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

The mode of propagation in which the electromagnetic waves radiated from an antenna, directed upwards at large angles, gets reflected by the ionosphere back to earth is called sky wave propagation or ionospheric propagation. The corresponding waves are called sky waves.

48. A single reflection helps the radio waves to travel a distance of approximately_____ Km

1. 2000
2. 4000
3. 3000
4. 1000

Explanation

Extremely long-distance communication is also possible as the radio waves can undergo multiple reflections between the earth and the ionosphere. A single reflection helps the radio waves to travel a distance of approximately 4000 km.

49. Ionosphere distance of approximately____ km and spreads up to____ km above the Earth surface

1. 40, 400
2. 50, 100
3. 50, 400
4. 80, 300

Explanation

Ionosphere acts as a reflecting surface. It is at a distance of approximately 50 km and spreads up to 400 km above the Earth surface. Due to the absorption of ultraviolet rays, cosmic ray, and other high energy radiations like α, β rays from sun, the air molecules in the ionosphere get ionized

50. The phenomenon of bending the radio waves back to earth is_____

1. Refraction
2. Reflection
3. Total internal reflection
4. Total internal refraction

Explanation

Due to the absorption of ultraviolet rays, cosmic ray, and other high energy radiations like α, β rays from sun, the air molecules in the ionosphere get ionized. This produces charged ions and these ions provide a reflecting medium for the reflection of radio waves or communication waves back to Earth within the permitted frequency range. The phenomenon of bending the radio waves back to earth is nothing but the total internal reflection.

51. The shortest distance between the transmitter and the point of reception of the sky wave along the surface is called____

1. Skid distance
2. Skip distance
3. Skin distance
4. None

Explanation

The shortest distance between the transmitter and the point of reception of the sky wave along the surface is called as the skip distance.

52. Lesser the frequency, skip distance is_____

1. Higher
2. Lesser
3. Zero
4. None

Explanation

The higher the frequency, higher is the skip distance and for a frequency less than the critical frequency, skip distance is zero.

53. The electromagnetic waves of very high frequencies above___ MHz are called as space waves.

1. 20
2. 30
3. 3
4. 120

Explanation

The process of sending and receiving information signal through space is called space wave communication. The electromagnetic waves of very high frequencies above 30 MHz are called as space waves.

54. Which of the following are the advantages of microwaves over radio waves?

1. High data rate
2. Larger bandwidth
3. Better directivity
4. Large antenna size
5. 1, 2, 4
6. 2, 3, 4
7. 1, 2, 3
8. All the above

Explanation

Microwaves having high frequencies (super high frequency band) are used against radio waves due to certain advantages: larger bandwidth, high data rates, better directivity, small antenna size, low power consumption, etc.

55. What is the radius of earth?

1. 5400 Km
2. 6400 Km
3. 4500 Km
4. 3300 km

Explanation

The range or distance (d) of coverage of the propagation depends on the height (h) of the antenna given by the equation, where R is the radius of the Earth and it is 6400 km.

56. A transmitting antenna has a height of 40 m and the height of the receiving antenna is 30 m. What is the maximum distance between them for line-of-sight communication? The radius of the earth is 6.4×10⁶ m.

1. 54.54 Km
2. 42. 21 Km
3. 37.71 Km
4. 23.37 Km

Explanation

57. Which of the following are advantages of fibre cables?

1. Fiber cables are very thin and weigh lesser than copper cable
2. Fiber optic system is immune to electrical interferences
3. Fiber optic cables are cheaper than copper cables.
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Merits

i) Fiber cables are very thin and weigh lesser than copper cables. ii) This system has much larger band width. This means that its information carrying capacity is larger. iii) Fiber optic system is immune to electrical interferences. iv) Fiber optic cables are cheaper than copper cables.

58. Recent developments in optical communication provide the data speed at the rate of __ Gbps

1. 10
2. 5
3. 15
4. 25

Explanation

Fiber optic cables provide the fastest transmission rate compared to any other form of transmission. It can provide data speed of 1 Gbps for homes and business. Multimode fibers operate at the speed of 10 Mbps. Recent developments in optical communication provide the data speed at the rate of 25 Gbps

59. Which of the following statement is correct?

1. The satellite communication is a mode of communication of signal between transmitter and receiver via satellite
2. The message signal from the Earth station is transmitted to the satellite on board via an uplink
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

The satellite communication is a mode of communication of signal between transmitter and receiver via satellite. The message signal from the Earth station is transmitted to the satellite on board via an uplink (frequency band 6 GHz), amplified by a transponder and then retransmitted to another Earth station via a downlink (frequency band 4 GHz)

60. Which of the following are technology in mobile communication?

1. WiMAX
2. Edge
3. Wibro
4. All the above

Explanation

Recently, the mobile communication technology has evolved through various stages like 2G, 3G, 4G, 5G, WiMAX, Wibro, EDGE, GPRS and many others. This helps to increase the speed of communication and the range of coverage. The connectivity issues have decreased with reliable and secure connections. The GPS (Global Positioning System) and GSM (Global System for Mobile communication) technology play an important role in mobile communication. This increases the utilization of bandwidth of the network, sharing of the networks, error detections, etc. Many methods like digital switching, TDMA, CDMA have been used to ease the communication process.

61. Identify the Incorrect Match.

A. Radio i) 1887

B. Telephone ii) 1976

C. Telegraph iii) 1844

a) i only

b) ii only

c) iii only

d) None of the above

Explanation

The communication industry is one of the largest in size and is the oldest since communication through telegraph (1844), telephone (1876), and Radio (1887) started centuries back.

62. Which of this parameter is not varied to produce a modulation in the signals?

a) Time

b) Amplitude

c) Frequency

d) Phase

Explanation

There are 3 types of modulation based on which parameter is modified. They are (i) amplitude modulation, (ii) frequency modulation and (iii) phase modulation.

63. Which of the following is varied in the amplitude modulation scheme?

a) Amplitude of carrier

b) Phase of the carrier

c) Amplitude of baseband

d) Frequency of the carrier

Explanation

In the Amplitude modulation scheme the amplitude of the carrier is modified in proportion to the amplitude of the baseband signal.

64. Which of the following is not a limitation of Amplitude modulation?

a) Low efficiency

b) High noise level

c) Reduced noise

d) Small operating range

Explanation

Limitations of AM: Noise level is high, Low efficiency and Small operating range.

65. In which of these conditions the frequency of the baseband signal is zero?

a) Normal frequency

b) Centre frequency

c) Resting frequency

d) All the above

Explanation

When the frequency of the baseband signal is zero (no input signal), there is no change in the frequency of the carrier wave. It is at its normal frequency and is called as centre frequency or resting frequency

66. Which of the following is not a limitation of Frequency modulation?

a) Wider channel requirement

b) Small bandwidth usage

c) Costly and complex systems

d) Covers less area than AM.

Explanation

Limitations of FM: FM requires a much wider channel, FM transmitters and receivers are more complex and costly. In FM reception, less area is covered compared to AM.

67. Which of the following characteristics suits with the Phase modulation scheme?

a) High transmission speed.

b) High bandwidth requirement

c) Simple system

d) Larger area coverage

Explanation

In PM, more information can be sent in a given bandwidth. Hence, phase modulation provides high transmission speed on a given bandwidth.

68. Which of these is located in the broadcasting station?

a) Demodulator

b) Decoder

c) Transmitter

d) Receiver

Explanation

The transmitter is located at the broadcasting station.

69. For which of these reasons the power level of the signal is increased in the Power amplifier?

a) To increase the system efficiency

b) To cover large distance

c) To reduce the noise interference

d) To increase the amplitude and frequency ranges

Explanation

Power amplifier: It increases the power level of the electrical signal in order to cover a large distance.

70.Choose the correct order of components in the transmission side of the system?

a) Input Transducer, Amplifier, Modulator, Power Amplifier, Channel

b) Amplifier, Input Transducer, Modulator, Channel, Power Amplifier

c) Input Transducer, Power Amplifier, Modulator, Amplifier, Channel

d) Channel, Input Transducer, Amplifier, Power Amplifier, Modulator

Explanation

71. Choose the correct statements.

i) Wire line communication uses wires, cables and optical fibers for communication.

ii) Wire line communication can be used for long distance transmission.

a) i only

b) ii only

c) Both i and ii

d) Neither i nor ii

Explanation

Wire line communication (point to point communication) uses mediums like wires, cables and optical fibers. These systems cannot be used for long distance transmission as they are connected physically.

72. Which of these are used to extract the baseband signal in the receiver?

a) Decoder

b) Differentiator

c) Demodulator

d) Digital switch

Explanation

The receiver consists of electronic circuits like demodulator, amplifier, detector etc. The demodulator extracts the baseband signal from the modulated signal. Then the baseband signal is detected and amplified using amplifiers.

73. Which of the following statement is correct?

a) Repeaters are used to increase the range or distance.

b) Repeater transmits, demodulate and retransmit the signals.

c) Repeater is a combination of receiver and transmitter.

d) Communication satellite in space is the example of repeater.

Explanation

Repeaters are used to increase the range or distance through which the signals are sent. It is a combination of transmitter and receiver. The signals are received, amplified and retransmitted with a carrier signal of different frequency to the destination. The best example is the communication satellite in space.

74. Define range.

a) Maximum distance between the source and the destination with sufficient strength.

b) Maximum possible frequency ranges for transmission.

c) Minimum distance between source and destination without noise interference.

d) All possible frequency range available for communication.

Explanation

Range: It is the maximum distance between the source and the destination up to which the signal is received with sufficient strength.

75. Which of these parameters decide the type of communication system?

a) Amplitude and signal strength

b) Energy levels of the signals

c) Nature of the frequency band

d) Type of channel

Explanation

The type of communication system depends on the nature of the frequency band for a given signal.

76. What is the value of the channel bandwidth in amplitude modulation technique?

a) Twice the signal frequency

b) Half the value of the minimum possible frequency

c) Equal to the maximum frequency of the sample

d) Less than the signal frequency.

Explanation

In amplitude modulation, the channel bandwidth is twice the signal frequency. Therefore, it is required to reduce the channel bandwidth to accommodate more number of channels in the available electromagnetic spectrum. In some applications, modulation is selected based on this.

77. Which of the following decides the efficiency of the radiation of signals?

a) Signal strength

b) Size of the antenna

c) Number of channels

d) Maximum frequency range of signal

Explanation

The size of the antenna plays a major role in deciding the efficiency of the radiation of signals.

78.Which of the following are the reasons for signal attenuation in the ground wave propagation?

a) Increased distance

b) Energy absorption by earth

c) Tilting of the wave

d) All the above

Explanation

During ground wave propagation, the electrical signals are attenuated over a distance. some reasons for attenuation are as follows ,increasing distance, absorption of energy by the earth, tilting of the wave.

79. What range of frequency can easily penetrate through ionosphere without any reflection?

a) < 3MHz

b) > 30 MHz

c) < 0.3 GHz

d) 10 GHz

Explanation

The frequency range of EM waves in this ground mode of propagation is 3 to 30 MHz. EM waves of frequency more than 30 MHz can easily penetrate through the ionosphere and does not undergo reflection

80. Which of this communication system does not use space wave propagation?

a) Television

b) RADAR

c) Telephone

d) Satellite

Explanation

The communication systems like television telecast, satellite communication and RADAR are based on space wave propagation.

81. What is the uplink frequency range of the message signal from the earth?

a) 2 MHz frequency band

b) 6 GHz frequency band

c) 60 GHz frequency band

d) 2THz frequency band

Explanation

The message signal from the Earth station is transmitted to the satellite on board via an uplink (frequency band 6 GHz), amplified by a transponder and then retransmitted to another Earth station via a downlink (frequency band 4 GHz)

82. Which of these is termed as radio repeater in sky?

a) Satellites

b) Space stations

c) Rockets

d) Radar

Explanation

A communication satellite relays and amplifies such radio signals via transponder to reach distant and far off places using uplinks and downlinks. It is also called as a radio repeater in sky.

83. Based on which of the following categories satellites are classified?

a) Design

b) Complexity

c) Application

d) Range

Explanation

Satellites are classified into different types based on their applications.

84.By measuring which of the following quantities satellites predict rain and storms?

a) Cloud mass

b) Precipitation

c) Atmospheric pressure

d) Ionization levels

Explanation

Weather Satellites: They are used to monitor the weather and climate of Earth. By measuring cloud mass, these satellites enable us to predict rain and dangerous storms like hurricanes, cyclones etc.

85. What is the frequency range of light?

a) 400 THz – 790 THz

b) 250 MHz- 750 GHz

c) 100 GHz – 500 GHz

d) Below 200 THz

Explanation

Light has very high frequency (400 THz – 790 THz) than microwave radio systems. The fibers are made up of silica glass or silicon dioxide which is highly abundant on Earth.

86. In which of these applications optical fibers are efficiently used?

a) Multiple channels

b) Single channel and isolated channels

c) Isolation from electrical and electromagnetic interference

d) Both a and c

Explanation

As fibers are not electrically conductive, it is preferred in places where multiple channels are to be laid and isolation is required from electrical and electromagnetic interference

87. Which of the following is not an application of optical fiber system?

a) To locate and sense the invisible objects.

b) International communication

c) Defense applications

d) Plant and traffic control

Explanation

Optical fiber system has a number of applications namely, international communication, inter-city communication, data links, plant and traffic control and defense applications.

88. Which of the following is not a merit of the fiber optic technology?

a) Fiber cables are very thin and weigh lesser than copper cables.

b) Fiber cable system has much larger band width and the information carrying capacity is larger.

c) Fiber optic cables are more fragile compared to copper wires.

d) Fiber optic system is immune to electrical interferences.

Explanation

Fiber optical communication: Merits: Fiber cables are very thin and weigh lesser than copper cables. This system has much larger band width. This means that its information carrying capacity is larger. Fiber optic system is immune to electrical interferences. Fiber optic cables are cheaper than copper cables. Demerits: Fiber optic cables are more fragile when compared to copper wires. It is an expensive technology.

89. Choose the incorrect statements.

i) Radar stands for Radio Decoder and Rotating system.

ii) Radar is used to detect sense and locate distant objects.

iii) The angle, range or velocities which are invisible to the human eye can be determined using radar.

a) i only

b) ii only

c) iii only

d) All the above

Explanation

Radar basically stands for Radio Detection and Ranging System. It is one of the important applications of communication systems and is mainly used to sense, detect, and locate distant objects like aircraft, ships, spacecraft, etc. The angle, range or velocity of the objects that are invisible to the human eye can be determined

90. Which of the following are the applications of Mobile communication?

a) Personal communication with high speed.

b) To control various devices from a single device.

c) Internet usage

d) All the above

Explanation

Applications of Mobile communication: It is used for personal communication and cellular phones offer voice and data connectivity with high speed. Transmission of news across the globe is done within a few seconds. Using Internet of Things (IoT), it is made possible to control various devices from a single device. Example: home automation using a mobile phone. It enables smart classrooms, online availability of notes, monitoring student activities etc. in the field of education.

91. Which of the following methods are used for easy process in mobile communication?

a) Digital switching

b) Time Division Multiplexing

c) Code Division Multiple Access

d) All the above

Explanation

The GPS (Global Positioning System) and GSM (Global System for Mobile communication) technology play an important role in mobile communication. This increases the utilization of bandwidth of the network, sharing of the networks, error detections, etc. Many methods like digital switching, TDMA, CDMA have been used to ease the communication process.

92. Which of the following statements is not true regarding the GPS?

a) GPS stands for Global Positioning System.

b) Global positioning system is pure hardware system.

c) Global navigation satellite system offers geo location and time information.

d) GPS system works with the assistance of a satellite network.

Explanation

GPS stands for Global Positioning System. It is a global navigation satellite system that offers geo location and time information to a GPS receiver anywhere on or near the Earth. GPS system works with the assistance of a satellite network. Each of these satellites broadcasts a precise signal like an ordinary radio signal. These signals that convey the location data are received by a low-cost aerial which is then translated by the GPS software. The software is able to recognize the satellite, its location, and the time taken by the signals to travel from each satellite.

12th Science Lesson 11 Questions in English

11] Evolution

1. The present state of mankind on earth is the outcome of_____ evolutions

1. Chemical
2. Organic
3. Cultural
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

The term evolution is used to describe heritable changes in one or more characteristics of a population of species from one generation to the other. The present state of mankind on earth is the outcome of three kinds of evolution – chemical, organic and social or cultural evolution.

2. What is the age of Earth according to Radiometric dating of meteorites?

a) 4.5 – 4.6 billion years

b) 4.5 – 4.6 million years

c) 4.5 – 4.6 Trillion years

d) 4.5 – 4.6 Zillion years

Explanation

Radiometric dating of meteorites yields an estimated age for the solar system and for earth as around 4.5 – 4.6 billion years.

3. Which of the following statement is correct?

1. The new born earth remained inhospitable for at least few hundred million years
2. Water vapour released from the planet’s interior cooled and condensed to form oceans
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

The new born earth remained inhospitable for at least few hundred million years. At first it was too hot. This is because the collisions of the planetesimals that coalesced to form earth released much heat to melt the entire planet. Eventually outer surface of the earth cooled and solidified to form a crust. Water vapour released from the planet’s interior cooled and condensed to form oceans. Hence origin of life can be reconstructed using indirect evidences.

4. ______ states that life was created by a supernatural power, respectfully referred to as “God”

1. Theory of special creation
2. Theory of evolution
3. Theory of Darwin
4. Big Bang theory

Explanation

Theory of special creation states that life was created by a supernatural power, respectfully referred to as “God”. According to Hinduism, Lord Brahma created the Earth. Christianity, Islam and most religions believe that God created the universe, the plants and the animals.

5. ________ coined the term abiogenesis

1. George gregor Mendal
2. Thomas Huxley
3. Charles Darwin
4. Mendleev

Explanation

According to the theory of spontaneous generation or Abiogenesis, living organisms originated from non-living materials and occurred through stepwise chemical and molecular evolution over millions of years. Thomas Huxley coined the term abiogenesis.

6._____explains the origin of universe as a singular huge explosion in physical terms.

1. Theory of special creation
2. Theory of evolution
3. Theory of Darwin
4. Big Bang theory

Explanation

Big bang theory explains the origin of universe as a singular huge explosion in physical terms. The primitive earth had no proper atmosphere, but consisted of ammonia, methane, hydrogen and water vapour.

7. UV rays from the sun split up water molecules into___ and__

1. Nitrogen and Oxygen
2. Oxygen and Sulphur
3. Hydrogen and Oxygen
4. Nitrogen and Sulphur

Explanation

The temperature of the earth was extremely high. UV rays from the sun split up water molecules into hydrogen and oxygen. Gradually the temperature cooled and the water vapour condensed to form rain.

8. Ammonia and methane in the atmosphere combined with____ to form carbon-dioxide

1. Carbon
2. Oxygen
3. Hydrogen
4. Sulphur

Explanation

Rain water filled all the depressions to form water bodies. Ammonia and methane in the atmosphere combined with oxygen to form carbon-dioxide and other gases.

9. According to the____ life arose from pre-existing life

1. Theory of special creation
2. Theory of evolution
3. Theory of biogenesis
4. Big Bang theory

Explanation

According to the theory of biogenesis life arose from pre-existing life. The term biogenesis also refers to the biochemical process of production of living organisms This term was coined by Henry Bastian.

10. ________ suggested that the organic compounds could have undergone a series of reactions leading to more complex molecules.

1. Darwin
2. Oparin
3. Haldane
4. Henry Bastian

Explanation

Oparin (1924) suggested that the organic compounds could have undergone a series of reactions leading to more complex molecules. He proposed that the molecules formed colloidal aggregates or ‘coacervates’ in an aqueous environment.

11. ____ proposed that the primordial sea served as a vast chemical laboratory powered by solar energy

1. Darwin
2. Oparin
3. Haldane
4. Henry Bastian

Explanation

Haldane (1929) proposed that the primordial sea served as a vast chemical laboratory powered by solar energy. The atmosphere was oxygen free and the combination of CO2, NH3 and UV radiations gave rise to organic compounds.

12. Which of the following statement is correct?

1. The duration of the earth’s history has been divided into eras that include the Paleozoic, Mesozoic, and Cenozoic
2. Recent eras are further divided into periods, which are split into epochs.
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

The duration of the earth’s history has been divided into eras that include the Paleozoic, Mesozoic, and Cenozoic. Recent eras are further divided into periods, which are split into epochs. The geological time scale with the duration of the eras and periods with the dominant forms of life

13. Match the following

A.Permian 1. Earliest Amphibian

B.Mississippian 2. Origin of fishes

C.Silurian 3. Age of fishes

D.Devonian 4. Mammal like reptiles

1. 3, 1, 2, 4
2. 4, 1, 2, 3
3. 4, 1, 3, 2
4. 2, 3, 4, 1

Explanation

The six periods of Paleozoic era in order from oldest to the youngest are Cambrian (Age of invertebrates), Ordovician (fresh water fishes, Ostracoderms, various types of Molluscs), Silurian (origin of fishes), Devonian (Age of fishes, many types of fishes such as lung fishes, lobe finned fishes and ray finned fishes), Mississippian (earliest amphibians, Echinoderms), Pennsylvanian (earliest reptiles), Permian (mammal like reptiles)

14. ____ era called the Golden age of reptiles

1. Paleozoic
2. Mesozoic
3. Cenozoic
4. All the above

Explanation

Mesozoic era (dominance of reptiles) called the Golden age of reptiles, is divided into three periods namely, Triassic (origin of egg laying mammals), Jurassic (Dinosaurs were dominant on the earth, fossil bird – Archaeopteryx) and Cretaceous (extinction of toothed birds and dinosaurs, emergence of modern birds).

15. Cenozoic era (Age of mammals) is subdivided into___ periods

1. 4
2. 3
3. 2
4. 5

Explanation

Cenozoic era (Age of mammals) is subdivided into two periods namely Tertiary and Quaternary. Tertiary period is characterized by abundant mammalian fauna.

16. Match the following

A.Paleocene 1. origin of man from man like apes

B.Oligocene 2. placental mammals

C.Miocene 3. higher placental mammals

D.Pliocene 4. origin of first man like apes

1. 2, 3, 4, 1
2. 2, 1, 4, 3
3. 1, 3, 2, 4
4. 2, 4, 1, 3

Explanation

Tertiary period is characterized by abundant mammalian fauna. This period is subdivided into five epochs namely, Paleocene (placental mammals, Eocene (Monotremes except duck billed Platypus and Echidna, hoofed mammals and carnivores), Oligocene (higher placental mammals appeared), Miocene (origin of first man like apes) and Pliocene (origin of man from man like apes).

17. Which of the following statement is correct?

1. The age of fossils can be determined using two methods namely, relative dating and absolute dating
2. Relative dating is used to determine a fossil by comparing it to similar rocks and fossils of known age
3. Absolute dating is used to determine the precise age of a fossil by using radiometric dating to measure the decay of isotopes
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

The age of fossils can be determined using two methods namely, relative dating and absolute dating. Relative dating is used to determine a fossil by comparing it to similar rocks and fossils of known age. Absolute dating is used to determine the precise age of a fossil by using radiometric dating to measure the decay of isotopes.

18. ____ are lipids in a solution that can self-assemble into a lipid bilayer

1. Liposomes
2. Anti-somes
3. Protein
4. Antigen

Explanation

Liposomes are lipids in a solution that can self-assemble into a lipid bilayer. Some of the proteins inside the liposomes acquired the properties of enzymes resulting in fast multiplication of molecules.

19. Which of the following statement is correct?

1. Abiotically produced molecules can spontaneously self – assemble into droplets enclosing a watery solution
2. Scientists call these spheres as ‘protobionts’
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Abiotically produced molecules can spontaneously self-assemble into droplets that enclose a watery solution and maintain a chemical environment different from their surroundings. Scientists call these spheres as ‘protobionts’

20. Which of the following statement is correct?

1. The atmospheric oxygen combined with methane and ammonia to form CO2 and free nitrogen
2. The presence of the free O2 brought about the evolution of anaerobic respiration which could yield large amounts of energy by oxidation of food stuffs
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

The atmospheric oxygen combined with methane and ammonia to form CO2 and free nitrogen. The presence of the free O2 brought about the evolution of aerobic respiration which could yield large amounts of energy by oxidation of food stuffs. Thus, Prokaryotes and Eukaryotes evolved.

21. ____ are considered as ancestral to the modern bacteria and blue green algae

1. Monera
2. Protista
3. Clumps of nucleoproteins embedded in the cell substance
4. None

Explanation

Two major cell types that appeared during this time were significant. One form of the earliest cell contained clumps of nucleoproteins embedded in the cell substance. Such cells were similar to the Monera. They are considered as ancestral to the modern bacteria and blue green algae.

22. Which of the following statement is correct?

1. When the natural sources of food in the ocean declined in course of time the ancestors of Monera and Protista had to evolve different methods for food procurement
2. These may be summarized as parasitism, saprophytism predator or animalism and chemosynthesis or photosynthesis
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

When the natural sources of food in the ocean declined in course of time the ancestors of Monera and Protista had to evolve different methods for food procurement. These may be summarized as parasitism, saprophytism, predator or animalism and chemosynthesis or photosynthesis. When the number of photosynthetic organisms increased there was an increase in the free O2 in the sea and atmosphere.

23. Who paved way for understanding the possible synthesis of organic compounds?

1. Darwin
2. Urey
3. Urey and Miller
4. Miller

Explanation

Urey and Miller (1953), paved way for understanding the possible synthesis of organic compounds that led to the appearance of living organisms.

24. _______ is the study of prehistoric life through fossils

1. Entomology
2. Etymology
3. Paleontology
4. Lithography

Explanation

Paleontology is the study of prehistoric life through fossils. Fossils are described as the true witnesses of evolution or documents

25. Fossilization is the process by which plant and animal remains are preserved in_____

1. Metamorphic rocks
2. Sedimentary rocks
3. Igneous rocks
4. All the above

Explanation

Fossilization is the process by which plant and animal remains are preserved in sedimentary rocks. They fall under three main categories.

26. Which of the following statement is correct?

1. The original hard parts such as bones, teeth or shells are preserved as such in the earth’s atmosphere.
2. When marine animals die, their hard parts such as bones, shells, etc., are covered with sediments and are protected from further deterioration.
3. They get preserved as such as they are preserved in vast ocean; the salinity in them prevents decay
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

The original hard parts such as bones, teeth or shells are preserved as such in the earth’s atmosphere. This is the most common method of fossilization. When marine animals die, their hard parts such as bones, shells, etc., are covered with sediments and are protected from further deterioration. They get preserved as such as they are preserved in vast ocean; the salinity in them prevents decay. The sediments become hardened to form definite layers or strata. For example, Woolly Mammoth that lived 22 thousand years ago were preserved in the frozen coast of Siberia as such.

27. Which of the following minerals are involved in petrifaction type?

1. Iron pyrite
2. Calcium carbonate
3. Bicarbonate of sodium
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

The principle minerals involved in this petrifaction fossilization are iron pyrites, silica, calcium carbonate and bicarbonates of calcium and magnesium

28. Which of the following statement is correct?

1. When animals die the original portion of their body may be replaced molecule for molecule by minerals and the original substance being lost through disintegration
2. This method of fossilization is called petrifaction
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

When animals die the original portion of their body may be replaced molecule for molecule by minerals and the original substance being lost through disintegration. This method of fossilization is called petrifaction

29. Which of the following statement is correct?

1. Even after disintegration, the body of an animal might leave indelible impression on the soft mud which get hardened
2. Such impressions are called moulds
3. The cavities of the moulds may get filled up by hard minerals and get fossilized, which are called casts
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Even after disintegration, the body of an animal might leave indelible impression on the soft mud which later becomes hardened into stones. Such impressions are called moulds. The cavities of the moulds may get filled up by hard minerals and get fossilized, which are called casts. Hardened faecal matter termed as coprolites occur as tiny pellets. Analysis of the coprolites enables us to understand the nature of diet the pre-historic animals thrived on.

30. Which of the following statement is incorrect?

1. Similarities in structure between groups of organisms are accepted as indicators of relationship.
2. They can be studied under homologous organs, analogous organs, vestigial organs, connecting links and atavistic organs
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Similarities in structure between groups of organisms are accepted as indicators of relationship. For example, a comparative study of the forelimbs of different vertebrates exhibits a fundamental plan of similarity in structure. These relationships can be studied under homologous organs, analogous organs, vestigial organs, connecting links and atavistic organs.

31. Which of the following are similar bones in forelimbs of different animals that show similarity?

1. Femoral
2. Carpals
3. Humerus
4. Ulna
5. 1, 2, 4
6. 2, 3, 4
7. 1, 3, 4
8. All the above

Explanation

In vertebrates, comparative anatomical studies reveal a basic plan in various structures such as fore limbs and hind limbs. Fore limbs of vertebrates exhibit anatomical similarity with each other and is made of similar bones such as humerus, radius, ulna, carpals, metacarpals and phalanges.

32. Structures which are similar in origin but perform different functions are called____

1. Homologous structures
2. Analogous structures
3. Vestigial organs
4. Connecting link

Explanation

Structures which are similar in origin but perform different functions are called homologous structures that brings about divergent evolution

33. Which of the following statement is correct?

1. Thorn of Bougainvillea and the tendrils of Curcurbita and Pisum sativum represent homology
2. The thorn in former is used as a defence mechanism from grazing animals and the tendrils of latter is used as a support for climbing
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Similarly, the thorn of Bougainvillea and the tendrils of Curcurbita and Pisum sativum represent homology. The thorn in former is used as a defence mechanism from grazing animals and the tendrils of latter is used as a support for climbing.

34. Organs having different structural patterns but similar function are termed as___

1. Homologous structures
2. Analogous structures
3. Vestigial organs
4. Connecting link

Explanation

Organs having different structural patterns but similar function are termed as analogous structures. For example, the wings of birds and insects are different structurally but perform the same function of flight that brings about convergent evolution.

35. Which of the following are the examples of convergent evolution?

1. Eyes of human
2. Eyes of octopus
3. Flippers of penguin
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Other examples of analogous organs (convergent evolution) include the eyes of the Octopus and of mammals and the flippers of Penguins and Dolphins.

36. Which of the following is not analogous evolution?

1. Root modification in sweet potato
2. Stem modification in potato
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Root modification in sweet potato and stem modification in potato are considered as analogous organs. Both of these plants have a common function of storage of food.

37. Structures that are of no use to the possessor, and are not necessary for their existence are called__

1. Homologous structures
2. Analogous structures
3. Vestigial organs
4. Connecting link

Explanation

Structures that are of no use to the possessor, and are not necessary for their existence are called vestigial organs.

38. Which of the following statement is incorrect?

1. Vestigial organs may be considered as remnants of structures which were well developed and functional in the ancestors
2. These organs disappeared in course of evolution due to their over utilization
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Vestigial organs may be considered as remnants of structures which were well developed and functional in the ancestors, but disappeared in course of evolution due to their non-utilization.

39. Human appendix is the remnant of____ which is functional in the digestive tract of herbivorous animals

1. Colon
2. Caecum
3. Rectum
4. Anus

Explanation

Human appendix is the remnant of caecum which is functional in the digestive tract of herbivorous animals like rabbit.

40. _____ digestion takes place in the caecum of these animals

1. Protein
2. Fat
3. Cellulose
4. Carbohydrate

Explanation

Cellulose digestion takes place in the caecum of these animals. Due to change in the diet containing less cellulose, caecum in human became functionless and is reduced to a vermiform appendix, which is vestigial.

41. Which of the following are vestigial organs in human body?

1. Wisdom tooth
2. Eye
3. Body hair
4. Coccyx
5. 1, 2, 4
6. 2, 3, 4
7. 1, 3, 4
8. All the above

Explanation

Other examples of vestigial organs in human beings include coccyx, wisdom teeth, ear muscles, body hair, mammae in male, nictitating membrane of the eye, etc.,

42. The organisms which possess the characters of two different groups are called____

1. Homologous structures
2. Analogous structures
3. Vestigial organs
4. Connecting link

Explanation

The organisms which possess the characters of two different groups (transitional stage) are called connecting links. Example Peripatus (connecting link between Annelida and Arthropoda), Archeopteryx (connecting link between Reptiles and Aves).

43. Sudden appearance of_____ in highly evolved organisms is called atavistic organs

1. Homologous structures
2. Analogous structures
3. Vestigial organs
4. Connecting link

Explanation

Sudden appearance of vestigial organs in highly evolved organisms is called atavistic organs. Example, presence of tail in a human baby is an atavistic organ.

44. _____ deals with the study of the development of individual from the egg to the adult stage

1. Etymology
2. Embryology
3. Entomology
4. Paleantology

Explanation

Embryology deals with the study of the development of individual from the egg to the adult stage. A detailed study of the embryonic development of different forms makes us to think that there is a close resemblance during development.

45. Match the following

A.Two chambered heart 1. Crocodile

B.Three chambered heart 2. Fishes

C.Four chambered heart 3. Reptiles

1. 2, 3, 1
2. 1, 2, 3
3. 2, 1, 3
4. 3, 2, 1

Explanation

The development of heart in all vertebrates follows the same pattern of development as a pair of tubular structures that later develop into two chambered heart in fishes, three chambered in amphibians and in most reptiles and four chambered in crocodiles, birds and mammals; indicating a common ancestry for all the vertebrates

46. Who propounded the “biogenetic law or theory of recapitulation”?

1. Ernest Von Haeckel
2. Ernest Von Rutherford
3. Charles Darwin
4. Gergor Mendel

Explanation

Ernst Von Haeckel, propounded the “biogenetic law or theory of recapitulation” which states that the life history of an individual (ontogeny) briefly repeats or recapitulates the evolutionary history of the race (phylogeny). In other words “Ontogeny recapitulates Phylogeny”

47. Which of the following statement is correct?

1. The biogenetic law is not universal and it is now thought that animals do not recapitulate the adult stage of any ancestors.
2. The human embryo recapitulates the embryonic history and not the adult history of the organisms
3. The comparative study of the embryo of different animals shows structural similarities among themselves
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

The biogenetic law is not universal and it is now thought that animals do not recapitulate the adult stage of any ancestors. The human embryo recapitulates the embryonic history and not the adult history of the organisms. The comparative study of the embryo of different animals shows structural similarities among themselves.

48. Which of the following embryo start as a single cell?

1. Fish
2. Chick
3. Human
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

The embryos of fish, salamander, tortoise, chick and human start life as a single cell, the zygote, and undergo cleavage to produce the blastula, change to gastrula and are triploblastic. This indicates that all the above said animals have evolved from a common ancestor.

49. Molecular evolution is the process of change in the sequence composition of molecules such as__

1. DNA
2. RNA
3. Protein
4. 1, 3
5. 2, 3
6. 1, 2
7. All the above

Explanation

Molecular evolution is the process of change in the sequence composition of molecules such as DNA, RNA and proteins across generations. It uses principles of evolutionary biology and population genetics to explain patterns in the changes of molecules

50. Which of the following statement is incorrect?

1. One of the most useful advancement in the development of molecular biology is proteins and other molecules that control life processes are conserved among species
2. A slight change that occurs over time in these conserved molecules (DNA, RNA and protein) are often called molecular clocks
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

One of the most useful advancement in the development of molecular biology is proteins and other molecules that control life processes are conserved among species. A slight change that occurs over time in these conserved molecules (DNA, RNA and protein) are often called molecular clocks. Molecules that have been used to study evolution are cytochrome c (respiratory pathway) and rRNA (protein synthesis).

51. __________ was the first to postulate theory of evolution in his famous book ‘Philosophie Zoologique’

1. Darwin
2. Lamarck
3. Rutherford
4. Thompson

Explanation

Jean Baptiste de Lamarck, was the first to postulate the theory of evolution in his famous book ‘Philosophie Zoologique’ in the year 1809. There are two principles of Lamarckian theory.

52. Which of the following are example of theory of use and disuse?

1. Neck in giraffe
2. Absence of limb in snake
3. Hand in human
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

The theory of use and disuse – Organs that are used often will increase in size and those that are not used will degenerate. Neck in giraffe is an example of use and absence of limbs in snakes is an example for disuse theory.

53. Which of the following statement is correct?

1. Characters that are developed during the life time of an organism are called acquired characters
2. They are not inherited
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

The theory of inheritance of acquired characters – Characters that are developed during the life time of an organism are called acquired characters and these are then inherited.

54. Lamarck’s “Theory of Acquired characters” was disproved by____

1. Darwin
2. August Weismann
3. Augstein
4. Westminister

Explanation

Lamarck’s “Theory of Acquired characters” was disproved by August Weismann who conducted experiments on mice for twenty generations by cutting their tails and breeding them. All mice born were with tail.

55. Who among the following are followers of Lamarck?

1. Cope
2. Darwin
3. Osborn
4. Spencer
5. 1, 2, 4
6. 2, 3, 4
7. 1, 2, 3
8. 1, 3, 4

Explanation

The followers of Lamarck (Neo-Lamarckists) like Cope, Osborn, Packard and Spencer tried to explain Lamarck’s theory on a more scientific basis. They considered that adaptations are universal.

56. Which of the following statement is incorrect?

1. Organisms acquire new structures due to their adaptations to the changed environmental conditions
2. They argued that external conditions stimulate the somatic cells to produce certain ‘secretions’ which reach the sex cells through the blood
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Organisms acquire new structures due to their adaptations to the changed environmental conditions. They argued that external conditions stimulate the somatic cells to produce certain ‘secretions’ which reach the sex cells through the blood and bring about variations in the offspring.

57. Who explained the theory of evolution in his book?

1. Cope
2. Darwin
3. Osborn
4. Spencer

Explanation

Charles Darwin explained the theory of evolution in his book ‘The Origin of Species by Natural Selection’. During his journey around the Earth, he made extensive observations of plants and animals.

58. Who proved that fittest organisms can survive and leave more progenies than the unfit ones?

1. Darwin
2. Cope
3. Newton
4. Lamarck

Explanation

Darwin noted a huge variety and remarkable similarities among organisms and their adaptive features to cope up to their environment. He proved that fittest organisms can survive and leave more progenies than the unfit ones through natural selection.

59. Which of the following statement is correct?

1. All living organisms increase their population in larger number
2. Salmon fish produces about 28 million eggs during breeding season and if all of them hatch, the seas would be filled with salmon in few generations
3. Elephant, the slowest breeder that can produce 9 young ones in its life time
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

All living organisms increase their population in larger number. For example, Salmon fish produces about 28 million eggs during breeding season and if all of them hatch, the seas would be filled with salmon in few generations. Elephant, the slowest breeder that can produce six young ones in its life time can produce 6 million descendants at the end of 750 years in the absence of any check.

60. Which of the following are limiting factors for organisms according to Darwin?

1. Food
2. Space
3. Mate
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Organisms struggle for food, space and mate. As these become a limiting factor, competition exists among the members of the population. Darwin denoted struggle for existence in three ways.

61. Which of the following statement is correct?

1. Intra specific struggle between the same species for food, space and mate
2. Inter specific struggle with different species for food, space and mate
3. Struggle with the environment to cope with the climatic variations, flood, earthquakes, drought, etc.
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Darwin denoted struggle for existence in three ways – Intra specific struggle between the same species for food, space and mate. Inter specific struggle with different species for food and space. Struggle with the environment to cope with the climatic variations, flood, earthquakes, drought, etc.,

62. Which of the following statement is correct?

1. No two individuals are alike
2. There are variations even in identical twins
3. Even the children born of the same parents differ in colour, height, behaviour, etc.
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

No two individuals are alike. There are variations even in identical twins. Even the children born of the same parents differ in colour, height, behaviour, etc., The useful variations found in an organism help them to overcome struggle and such variations are passed on to the next generation.

63. According to whom, nature is the most powerful selective force?

1. Darwin
2. Charles
3. Lamarck
4. Mayer

Explanation

According to Darwin, nature is the most powerful selective force. He compared origin of species by natural selection to a small isolated group.

64. Which of the following statement is incorrect?

1. Darwin believed that the struggle for existence resulted in the survival of the fittest
2. Such organisms become better adapted to the changed environment
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Darwin believed that the struggle for existence resulted in the survival of the fittest. Such organisms become better adapted to the changed environment.

65. Which of the following are the objections against Darwin?

1. Darwin failed to explain the mechanism of variation
2. He focused on small fluctuating variations that are mostly non-heritable.
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Some objections raised against Darwinism were – • Darwin failed to explain the mechanism of variation. • Darwinism explains the survival of the fittest but not the arrival of the fittest. • He focused on small fluctuating variations that are mostly non-heritable. • He did not distinguish between somatic and germinal variations

66. Which of the following cannot be explained by Darwin?

1. Large tusks in extinct mammoths
2. Hand in Human
3. Oversized antlers in the extinct Irish deer
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Darwin could not explain the occurrence of vestigial organs, over specialization of some organs like large tusks in extinct mammoths, oversized antlers in the extinct Irish deer, etc.,

67. Who among the supported Darwin?

1. Wallace
2. Heinrich
3. Weismann
4. Cope
5. 1, 2, 4
6. 2, 3, 4
7. 1, 2, 3
8. All the above

Explanation

New facts and discoveries about evolution have led to modifications of Darwinism and is supported by Wallace, Heinrich, Haeckel, Weismann and Mendel.

68. Which of the following statement is incorrect?

1. Neo Darwinism is the interpretation of Darwinian evolution through Natural Selection as it has been modified since it was proposed.
2. This theory emphasizes the change in the frequency of genes in population arises due to mutation, variation, isolation and Natural selection.
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Neo Darwinism is the interpretation of Darwinian evolution through Natural Selection as it has been modified since it was proposed. This theory emphasizes the change in the frequency of genes in population arises due to mutation, variation, isolation and Natural selection.

69. Who put forth the mutation theory?

1. Mendel
2. Hugo de Vries
3. Wallace
4. Darwin

Explanation

Hugo de Vries put forth the Mutation theory. Mutations are sudden random changes that occur in an organism that is not heritable. De Vries carried out his experiments in the Evening Primrose plant (Oenothera Lamarckiana) and observed variations in them due to mutation.

70. Which of the following statement is incorrect?

1. According to de Vries, sudden and large variations were responsible for the origin of new species
2. Lamarck and Darwin believed in gradual accumulation of all variations as the causative factors in the origin of new species
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

According to de Vries, sudden and large variations were responsible for the origin of new species whereas Lamarck and Darwin believed in gradual accumulation of all variations as the causative factors in the origin of new species. Hugo de Vries believed that Mutations are random and directionless, but Darwinian variations are small and directional.

71. Which of the following are the features of mutation theory?

1. In naturally breeding populations, mutations occur from time to time
2. They are strictly subjected to natural selection
3. Mutations or discontinuous variation are transmitted to other generations
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Salient features of Mutation Theory:

Mutations or discontinuous variation are transmitted to other generations.

In naturally breeding populations, mutations occur from time to time.

There are no intermediate forms, as they are fully fledged.

They are strictly subjected to natural selection.

72. Sewell Wright, Fisher, Mayer, Huxley, Dobzhansky, Simpson and Haeckel explained Natural Selection in the light of___

1. Post Darwin discoveries
2. Post Lamarck discoveries
3. Post de Vries discoveries
4. None

Explanation

Sewell Wright, Fisher, Mayer, Huxley, Dobzhansky, Simpson and Haeckel explained Natural Selection in the light of Post-Darwinian discoveries. According to this theory gene mutations, chromosomal mutations, genetic recombination, natural selection and reproductive isolation are the five basic factors involved in the process of organic evolution.

73. ________ refers to the changes in the structure of the gene

1. Gene Mutation
2. Variation
3. Isolation
4. Natural selection

Explanation

Gene mutation refers to the changes in the structure of the gene. It is also called gene/ point mutation. It alters the phenotype of an organism and produces variations in their offspring.

74. Which of the following are included in chromosomal mutation?

1. Deletion
2. Addition
3. Translocation
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Chromosomal mutation refers to the changes in the structure of chromosomes due to deletion, addition, duplication, inversion or translocation. This too alters the phenotype of an organism and produces variations in their offspring

75. Genetic recombination is due to crossing over of genes during___

1. Mitosis
2. Meiosis
3. Amitosis
4. Ameiosis

Explanation

Genetic recombination is due to crossing over of genes during meiosis. This brings about genetic variations in the individuals of the same species and leads to heritable variations.

76. Which of the following statement is correct?

1. Natural selection does not produce any genetic variations but once such variations occur it favours some genetic changes while rejecting others
2. Reproductive isolation helps in preventing interbreeding between related organisms.
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Natural selection does not produce any genetic variations but once such variations occur it favours some genetic changes while rejecting others (driving force of evolution). Reproductive isolation helps in preventing interbreeding between related organisms.

77. Which of the following statement is correct?

1. Natural selection can be explained clearly through industrial melanism
2. Industrial melanism is a classical case of Natural selection exhibited by the peppered moth, Biston betularia
3. These were available in two colours, white and black
4. 1, 2
5. 2, 3
6. 1, 3
7. All the above

Explanation

Natural selection can be explained clearly through industrial melanism. Industrial melanism is a classical case of Natural selection exhibited by the peppered moth, Biston betularia. These were available in two colours, white and black. Before industrialization peppered moth both white and black coloured were common in England.

78. Which of the following statement is correct?

1. Pre-industrialization witnessed white coloured background of the wall of the buildings hence the white coloured moths escaped from their predator
2. Post industrialization, the tree trunks became dark due to smoke and soot let out from the industries
3. The black moths camouflaged on the dark bark of the trees and the white moths were easily identified by their predators
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Pre-industrialization witnessed white coloured background of the wall of the buildings hence the white coloured moths escaped from their predators. Post industrialization, the tree trunks became dark due to smoke and soot let out from the industries. The black moths camouflaged on the dark bark of the trees and the white moths were easily identified by their predators. Hence the dark coloured moth population was selected and their number increased when compared to the white moths.

79. Which of the following resulted in Artificial selection?

1. Human exploitation of ocean
2. Use of pesticides
3. Drugs
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Artificial selection is a by-product of human exploitation of forests, oceans and fisheries or the use of pesticides, herbicides or drugs.

80. Which of the following statement is incorrect?

1. The evolutionary process which produces new species diverged from a single ancestral form becomes adapted to newly invaded habitats is called adaptive radiation
2. Adaptive radiations are best exemplified in closely related groups that have evolved in relatively short time
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

The evolutionary process which produces new species diverged from a single ancestral form becomes adapted to newly invaded habitats is called adaptive radiation. Adaptive radiations are best exemplified in closely related groups that have evolved in relatively short time. Darwin’s finches and Australian marsupials are best examples for adaptive radiation.

81. Darwin’s finches common ancestor arrived on the Galapagos about____ years ago

1. 1 million
2. 2 million
3. 1 billion
4. 10 million

Explanation

Darwin’s finche common ancestor arrived on the Galapagos about 2 million years ago. During that time, Darwin’s finches have evolved into 14 recognized species differing in body size, beak shape and feeding behaviour. Changes in the size and form of the beak have enabled different species to utilize different food resources such as insects, seeds, nectar from cactus flowers and blood from iguanas, all driven by Natural selection.

82. Marsupials are found in____

1. Australia
2. Asia
3. Africa
4. Antarctica

Explanation

Marsupials in Australia and placental mammals in North America are two subclasses of mammals they have adapted in similar way to a particular food resource, locomotory skill or climate.

83. When did Marsupials and placental mammals got separated?

1. 100 million years ago
2. 10 million years ago
3. 1 billion years ago
4. 10 billion years ago

Explanation

Marsupials in Australia and placental mammals in North America were separated from the common ancestor more than 100 million year ago and each lineage continued to evolve independently. Despite temporal and geographical separation, marsupials in Australia and placental mammals in North America have produced varieties of species living in similar habitats with similar ways of life

84. Which of the following statement is correct?

1. Microevolution refers to the changes in allele frequencies within a population
2. Allele frequencies in a population may change due to four fundamental forces of evolution such as natural selection, genetic drift, mutation and gene flow
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Microevolution (evolution on a small scale) refers to the changes in allele frequencies within a population. Allele frequencies in a population may change due to four fundamental forces of evolution such as natural selection, genetic drift, mutation and gene flow.

85. Which of the following statement is correct?

1. Natural selection occurs when one allele makes an organism more or less fit to survive and reproduce in a given environment.
2. If an allele reduces fitness, its frequencies tend to drop from one generation to the next
3. The evolutionary path of a given gene i.e., how its allele’s change in frequency in the population across generation, may result from several evolutionary mechanisms acting at once
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Natural selection occurs when one allele (or combination of alleles of differences) makes an organism more or less fit to survive and reproduce in a given environment. If an allele reduces fitness, its frequencies tend to drop from one generation to the next. The evolutionary path of a given gene i.e., how its allele’s change in frequency in the population across generation, may result from several evolutionary mechanisms acting at once.

86. Which of the following statement about Stabilising Selection is correct?

1. This type of selection operates in a stable environment
2. There is speciation and the phenotypic stability is maintained within the population over generation
3. The organisms with average phenotypes survive whereas the extreme individuals from both the ends are eliminated.
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Stabilising Selection (centripetal selection):

This type of selection operates in a stable environment. The organisms with average phenotypes survive whereas the extreme individuals from both the ends are eliminated. There is no speciation but the phenotypic stability is maintained within the population over generation. For example, measurements of sparrows that survived the storm clustered around the mean, and the sparrows that failed to survive the storm clustered around the extremes of the variation showing stabilizing selection

87. Which of the following statement about Directional selection is correct?

1. The environment which undergoes gradual change is subjected to directional selection
2. Size differences between male and female sparrows is an example
3. Both male and female look alike externally but differ in body weight.
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Directional Selection: The environment which undergoes gradual change is subjected to directional selection. This type of selection removes the individuals from one end towards the other end of phenotypic distribution. For example, size differences between male and female sparrows. Both male and female look alike externally but differ in body weight. Females show directional selection in relation to body weight.

88. Which of the following statement about disruptive selection is correct?

1. When homogenous environment changes into heterogenous environment this type of selection is operational
2. The organisms of both the extreme phenotypes are selected whereas individuals with average phenotype are eliminated
3. This is rare type of selection
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Disruptive Selection (centrifugal selection): When homogenous environment changes into heterogenous environment this type of selection is operational. The organisms of both the extreme phenotypes are selected whereas individuals with average phenotype are eliminated. This results in splitting of the population into sub population/species. This is a rare form of selection but leads to formation of two or more different species. It is also called adaptive radiation. E.g. Darwin’s finches beak size in relation to seed size inhabiting Galapagos islands.

89. Which of the following statement is correct?

1. Movement of genes through gametes or movement of individuals in (immigration) and out (emigration) of a population is referred to as gene flow.
2. Gene flow is alone strong agent of evolution
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Movement of genes through gametes or movement of individuals in (immigration) and out (emigration) of a population is referred to as gene flow. Organisms and gametes that enter the population may have new alleles or may bring in existing alleles but in different proportions than those already in the population. Gene flow can be a strong agent of evolution.

90. Which of the following statement is incorrect?

1. Although mutation is the original source of all genetic variation, mutation rate for most organisms is low
2. Hence new mutations on an allele frequencies from one generation to the next is usually not large
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Although mutation is the original source of all genetic variation, mutation rate for most organisms is low. Hence new mutations on an allele frequencies from one generation to the next is usually not large.

91. Homo sapiens or modern human arose in_____

1. Australia
2. India
3. Africa
4. Brazil

Explanation

Homo sapiens or modern human arose in Africa some 25,000 years ago and moved to other continents and developed into distinct races. They had a brain capacity of 1300 – 1600 cc. They started cultivating crops and domesticating animals.

92.____ is considered as ancestor of modern Europeans

1. Cro-Magnon
2. Homo sapiens
3. Homo erectus
4. Hominion

Explanation

Cro-Magnon was one of the most talked forms of modern human found from the rocks of Cro-Magnon, France and is considered as the ancestor of modern Europeans. They were not only adapted to various environmental conditions, but were also known for their cave paintings, figures on floors and walls.

93. Neanderthal human was found in Neander Valley in____

1. France
2. Germany
3. India
4. Brazil

Explanation

Neanderthal human was found in Neander Valley, Germany with a brain size of 1400 cc and lived between 34,000 – 1,00,000 years ago. They differ from the modern human in having semierect posture, flat cranium, sloping forehead, thin large orbits, heavy brow ridges, protruding jaws and no chin.

94. Who among the used fire and buried their dead?

1. Neanderthal man
2. Homo habilis
3. Homo erectus
4. Australopithecus

Explanation

Neanderthal human used animal hides to protect their bodies, knew the use of fire and buried their dead. They did not practice agriculture and animal domestication.

95. ___ the first human like being was around 1.7 mya and was much closer to human in looks

1. Neanderthal man
2. Homo habilis
3. Homo erectus
4. Australopithecus

Explanation

Homo erectus the first human like being was around 1.7 mya and was much closer to human in looks, skull was flatter and thicker than the modern man and had a large brain capacity of around 900 cc. Homo erectus probably ate meat Homo ergaster and Homo erectus were the first to leave Africa.

96. Who had bipedal locomotion and used tools made of chipped stones?

1. Neanderthal man
2. Homo habilis
3. Homo erectus
4. Australopithecus

Explanation

Homo habilis lived about 2 mya. Their brain capacity was between 650 – 800cc, and was probably vegetarian. They had bipedal locomotion and used tools made of chipped stones.

97. Which of the following statement is correct?

1. Australopithecus lived in East African grasslands about 5 mya
2. They are called Australian ape man
3. He was about 2.5 meters tall with bipedal locomotion, omnivorous, semi erect, and lived in caves
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Australopithecus lived in East African grasslands about 5 mya and was called the Australian ape man. He was about 1.5 meters tall with bipedal locomotion, omnivorous, semi erect, and lived in caves. Low forehead, brow ridges over the eyes, protruding face, lack of chin, low brain capacity of about 350 – 450 cc, human like dentition, lumbar curve in the vertebral column were his distinguishing features.

98. Which of the following statement is correct?

1. Mammals evolved in the early Jurassic period, about 210 million years ago
2. Hominid evolution occurred in Asia and Africa
3. Hominids proved that human beings are superior to other animals and efficient in making tools and culture
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Mammals evolved in the early Jurassic period, about 210 million years ago (mya). Hominid evolution occurred in Asia and Africa. Hominids proved that human beings are superior to other animals and efficient in making tools and culture.

99. Which of the following statement is incorrect?

1. In nature, populations are usually evolving such as the grass in an open meadow, wolves in a forest and bacteria in a person’s body are all natural populations
2. Evolution does not mean that the population is moving towards perfection rather the population is changing its genetic makeup over generations.
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

In nature, populations are usually evolving such as the grass in an open meadow, wolves in a forest and bacteria in a person’s body are all natural populations. All of these populations are likely to be evolving some of their genes. Evolution does not mean that the population is moving towards perfection rather the population is changing its genetic makeup over generations. For example in a wolf population, there may be a shift in the frequency of a gene variant for black fur than grey fur. Sometimes, this type of change is due to natural selection or due to migration or due to random events.

100. Which of the following statement is correct?

i) As per the theory of spontaneous generation or Abiogenesis, living organisms

originated from non-living materials.

ii) stepwise chemical and molecular evolution created living materials from non-living materials.

a) i only

b) ii only

c) Both i and ii

d) Neither i nor ii

Explanation

According to the theory of spontaneous generation or Abiogenesis, living organisms

originated from non-living materials and occurred through stepwise chemical and

molecular evolution over millions of years.

101. Which of the following is not correct regarding the primitive earth?

a) No proper atmosphere.

b) Ammonia, Methane and hydrogen were present.

c) No traces of water vapour.

d) Earth temperature was very high.

Explanation

The primitive earth had no proper atmosphere, but consisted of ammonia, methane, hydrogen and water vapour. The temperature of the earth was extremely high.

102. According to Oparin concept in which of these environment molecules formed colloidal aggregates?

a) Atmospheric

b) High temperature

c) Aqueous

d) Plains

Explanation

Oparin (1924) suggested that the organic compounds could have undergone a series of reactions leading to more complex molecules. He proposed that the molecules formed colloidal aggregates or ‘coacervates’ in an aqueous environment.

103. Which of these term coined by Haldine became the powerful symbol of origin of life?

a) Prebiotic soup

b) Golden age

c) Biotic plates

d) Ginkgos

Explanation

Haldane coined the term prebiotic soup and this became the powerful symbol of the Oparin-Haldane view on the origin of life (1924-1929).

104. Which of these period witnesses decline of mammals and human social life beginning?

a) Devonian

b) Tertiary

c) Quaternary

d) Permian

Explanation

Quaternary period witnessed decline of mammals and beginning of human social life.

105. Choose the Incorrect stataments.

i) The age of fossils can be determined by various methodologies.

ii) Relative dating is used to determine a fossil by comparing it to similar rocks and fossils of known age.

iii) Absolute dating is used to determine the precise age of a fossil by using radiometric dating.

a) i only

b) ii only

c) iii only

d) All the above

Explanation

The age of fossils can be determined using two methods namely, relative dating and absolute dating. Relative dating is used to determine a fossil by comparing it to similar rocks and fossils of known age. Absolute dating is used to determine the precise age of a fossil by using radiometric dating to measure the decay of isotopes.

106. Which of the following method is the most common method of fossilization?

a) Actual remains

b) Natural moulds and casts

c) Petrifaction

d) All the above

Explanation

Actual remains – The original hard parts such as bones, teeth or shells are preserved as such in the earth’s atmosphere. This is the most common method of fossilization.

107. By which of these change in frequency of genes in population does not arise?

a) Mutation

b) Extinction

c) Isolation

d) Natural selection

Explanation

New facts and discoveries about evolution have led to modifications of Darwinism and is supported by Wallace, Heinrich, Haeckel, Weismann and Mendel. This theory emphasizes the change in the frequency of genes in population arises due to mutation, variation, isolation and Natural selection.

108. Which of the following is not a basic factor of modified darwanisim?

a) Natural selection

b) Phenotype modification

c) Gene mutations

d) genetic recombinations

Explanation

According to this new darwinisims theory gene mutations, chromosomal mutations, genetic recombinations, natural selection and reproductive isolation are the five basic factors involved in the process of organic evolution.

109. Which of the following prevents the interbreeding between related organisms?

a) Reproductive isolation

b) Adaptive radiation

c) Genetic drift

d) Species extinction

Explanation

Reproductive isolation helps in preventing interbreeding between related organisms.

110. By which of these mechanism chromosomal mutation changes the structure?

a) Addition / Deletion

b) Duplication

c) Translocation

d) All the above

Explanation

Chromosomal mutation refers to the changes in the structure of chromosomes due to deletion, addition, duplication, inversion or translocation. This too alters the phenotype of an organism and produces variations in their offspring

111. Choose the correct ststements regarding genetic drift.

i) Genetic drift is a mechanism of evolution where allele frequencies of a population does not change over generation.

ii) Genetic drift occurs in a small population only.

iii) May result in a loss of some alleles and fixation of other alleles.

a) i only

b) ii only

c) iii only

d) All the above

Explanation

Genetic drift is a mechanism of evolution in which allele frequencies of a population change over generation due to chance (sampling error). Genetic drift occurs in all population sizes, but its effects are strong in a small population. It may result in a loss of some alleles (including beneficial ones) and fixation of other alleles.

112. Which of the following is not included in the Hardy Weinberg’s assumptions?

a) Selected mating

b) No mutation

c) No natural selection

d) Large population size

Explanation

Hardy Weinberg’s assumptions include :

No mutation – No new alleles are generated by mutation nor the genes get duplicated or deleted.

Random mating – Every organism gets a chance to mate and the mating is random with each other with no preferences for a particular genotype.

No gene flow – Neither individuals nor their gametes enter (immigration) or exit (emigration) the population.

Very large population size – The population should be infinite in size.

No natural selection– All alleles are fit to survive and reproduce.

113. Choose the correct statements.

i) Hominid evolution occurred in Asia and Africa.

ii) Hominids proved that human beings are superior to other animals.

a) i only

b) ii only

c) Both i and ii

d) Neither i nor ii

Explanation

Hominid evolution occurred in Asia and Africa. Hominids proved that human beings are superior to other animals and efficient in making tools and culture.

114. Identify the incorrect Match.

A. Homo habilis i) Chipped stones

B. Ramapithecus ii) Ate meat

C. Dryopithecus iii) Walked like gorillas

D. Homo erectus iv) First to leave Africa

a) i only

b) ii only

c) iii only

d) iv only

Explanation

Dryopithecus and Ramapithecus were hairy and walked like gorillas and chimpanzees. Ramapithecus is regarded as a possible ancester of Australopithecus and therefore of modern humans. They were vegetarians. Australopithecus lived in East African grasslands about 5 mya and was called the Australian ape man. He was about 1.5 meters tall with bipedal locomotion, omnivorous, semi erect, and lived in caves. Homo habilis lived about 2 mya. Their brain capacity was between 650 – 800cc, and was probably vegetarian. They had bipedal locomotion and used tools made of chipped stones.Homo erectus the first human like being was around 1.7 mya and was much closer to human in looks, skull was flatter and thicker than the modern man and had a large brain capacity of around 900 cc. Homo erectus probably ate meat Homo ergaster and Homo erectus were the first to leave Africa.

115. What is an isolating barrier?

a) Environmental conditions that stops interbreeding.

b) Evolved character of two species that stops them from interbreeding.

c) Species breed to evolve in a new environment.

d) Non evolved characters allows to breed among themselves.

Explanation

An isolating barrier is any evolved character of the two species that stops them from interbreeding. Several kinds of isolating barriers are distinguished. The most important distinction is Prezygotic and post zygotic isolation.

116. Choose the correct statements.

i)Prezygotic mechanisms allow two species to come in contact.

ii) Post zygotic mechanisms are those which act before fertilization.

iii) Post zygotic mechanisms include hybrid sterility, hybrid inviability and hybrid breakdown.

a) i only

b) ii only

c) iii only

d) All the above

Explanation

Prezygotic mechanisms include those which prevent two species from coming into contact. This includes ecological, seasonal, ethological and morphological. Post zygotic mechanisms are those which act after fertilization that include hybrid sterility, hybrid inviability and hybrid breakdown.

117. Which of the following is not correct in the seasonal isolation?

i) The differences in the breeding seasons prevents the interbreeding.

ii) Species identity is not maintained due to the differences in seasons.

a) i only

b) ii only

c) Both i and ii

d) Neither i nor ii

Explanation

Seasonal isolation – In this type of isolation, difference in the breeding seasons prevents interbreeding. E.g. Toad, Bufo americanus breeds much early in the spring; whereas Bufo fowleri breeds very late in the season. They are able to maintain their species identity because of the differences in the breeding seasons.

118. Which of these prevent the fertilization in the cytological isolation?

a) Change in temperature and humidity

b) Differences in chromosome numbers

c) Sesaonal changes

d) Environmental hurdles

Explanation

Cytological isolation – Fertilization does not take place due to the differences in the chromosome numbers between the two species, the bull frog Rana catesbiana and gopher frog Rana areolata.

119. Which is considered as the fundamental process in evolution?

a) Speciation

b) Mutation

c) Extinction

d) Separation

Explanation

The process by which one species evolves into one or more different species is called speciation. A.E. Emerson defines species as a ‘genetically distinctive, reproductively isolated natural population’. Speciation is a fundamental process in evolution. Evolution of a new species in a single lineage is called an agenesis / phyletic speciation. If one species diverges to become two

or more species it is cladogenesis or divergentevolution.

120. Choose the Incorrect statements regarding the sympatric separation.

a) Mode of speciation through which new species form from a single ancestral species.

b) New species and the ancestral species continue to inhabit the same geographical region.

c) New species formed can breed with the parent population.

d) Two or more species are involved.

Explanation

Sympatric speciation/ Reproductive isolation : It is a mode of speciation through which new species form from a single ancestral species while both species continue to inhabit the same geographical region. Two or more species are involved. New species formed due to genetic modification in the ancestor that is naturally selected can no longer breed with the parent population. Sexual isolation is strongest.

121. Define phenotypic plasticity?

a) Single geneotype producing more than one phenotype.

b) Single genotype able produce another single phenotype.

c) Two geneotype combined and produced as a single phenotype.

d) More than one genotype producing a single geneotype.

Explanation

Phenotypic plasicity is the ability of single genotype to produce more than one phenotype.

122. Which of the following is not a barrier in the geographical speciation?

a) Separation

b) Extinction

c) Migration

d) Mountain formation

Explanation

Allopatric speciation/ Geographical speciation One species becomes two species due to geographical barriers hence new species is evolved e.g. Darwin’s finches. The barriers are land separation, migration or mountain formation.

123. Choose the correct statements.

i) Extinction is not common as species can always adapt to environmental changes.

ii) The impact of extinction can be considered at five levels.

1. i only
2. ii only
3. Both i and ii
4. Neither i nor ii

Explanation

Extinction was common if not inevitable because species could not always adapt to

large or rapid environmental changes. The impact of extinction can conveniently be

considered at three levels. Species extinction, Mass extinction, Global extinction.

124. By which of these species extinction eliminates an entire species?

a) Environmental events

b) Non availability of food

c) Resource unavailability

d) All the above

Explanation

Species extinction eliminates an entire species, by an environmental event (flood

etc.,) or by biological event (disease or non availability of food resource half or more).

125. Which of these concept is explained by the K-T extinction tables?

a) Species extinction

b) Mass extinction

c) Global extinction

d) All the above

Explanation

Mass extinction eliminates half or more species in a region or ecosystem, as might

occur following a volcanic eruption. Five major mass extinction that occurred since

the Cambrian period. This mass extinction is often referred to as K-T extinction.

K-T Extinction refers to the German word Cretaceous and Tertiary periods.

12th Science Lesson 12 Questions in English

12] Reproduction in Organisms

1. Which of the following are involved in life cycle of living organism?

1. Birth
2. Growth
3. Maturation
4. Reproduction
5. 1, 2, 4
6. 2, 3, 4
7. 1, 3, 4
8. All the above

Explanation

Living organisms show a life cycle involving birth, growth, development, maturation, reproduction and death.

2. Which of the following statement is correct?

1. Reproduction is the fundamental feature of all living organisms
2. It is a biological process by which organisms produce their young ones.
3. The young ones grow and mature to repeat the process.
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Reproduction is the fundamental feature of all living organisms. It is a biological process by which organisms produce their young ones. The young ones grow and mature to repeat the process. Thus reproduction results in continuation of species and introduces variations in organisms, which are essential for adaptation and evolution of their own kind.

3. Which of the following process are involved in modes of reproduction?

1. Synthesis of RNA
2. Replication of DNA
3. Nitrogen cycle
4. Cell division
5. 1, 2, 4
6. 2, 3, 4
7. 1, 3, 4
8. All the above

Explanation

All modes of reproduction have some basic features such as synthesis of RNA and proteins, replication of DNA, cell division and growth, formation of reproductive units and their fertilization to form new individuals.

4. How many major modes of reproduction are there?

1. 3
2. 4
3. 2
4. 5

Explanation

Organisms exhibit two major modes of reproduction namely asexual reproduction and sexual reproduction.

5. Which of the following statement about Asexual reproduction is correct?

1. It involves gamete formation
2. Asexual reproduction is usually by amitotic or mitotic division of the somatic (body) cells
3. It is also known as somatogenic or blastogenic reproduction
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Reproduction by a single parent without the involvement of gamete formation is asexual reproduction and the offspring produced are genetically identical. Asexual reproduction is usually by amitotic or mitotic division of the somatic (body) cells, hence is also known as somatogenic or blastogenic reproduction.

6. How many gametes are involved in sexual reproduction?

1. 4
2. 5
3. 2
4. 3

Explanation

When two parents participate in the reproductive process involving two types of gametes (ova and sperm), it is called sexual reproduction.

7. In which of the following Asexual reproduction is common?

1. Bacteria
2. Archaea
3. Protista
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Asexual reproduction is wide spread among different organisms. It is common in members of Protista, Bacteria, Archaea and in multicellular organisms with relatively simple organisation.

8. Which of the following statement about Asexual reproduction is correct?

1. The off-springs show “uniparental inheritance” with genetic variation
2. The different modes of asexual reproduction seen in animals are fission, budding, fragmentation and regeneration
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

The off-springs by Asexual reproduction show “uniparental inheritance” without any genetic variation. The different modes of asexual reproduction seen in animals are fission, budding, fragmentation and regeneration.

9. ____ is the division of the parent body into two or more identical daughter individuals

1. Fission
2. Fusion
3. Budding
4. Fragmentation

Explanation

Fission is the division of the parent body into two or more identical daughter individuals. Five types of fission are seen in animals. They are binary fission, multiple fission, plasmotomy, strobilation and sporulation.

10. Which of the following statement about Binary fission is correct?

1. In binary fission, the parent organism divides into two halves and each half forms a daughter individual.
2. The nucleus divides first a-mitotically or mitotically, followed by the division of the cytoplasm
3. The resultant off-springs are genetically identical to the parent.
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

In binary fission, the parent organism divides into two halves and each half forms a daughter individual. The nucleus divides first a-mitotically or mitotically (karyokinesis), followed by the division of the cytoplasm (cytokinesis). The resultant off-springs are genetically identical to the parent.

11. Depending on the plane of fission, binary fission is classified into____ types

1. 4
2. 3
3. 5
4. 2

Explanation

Depending on the plane of fission, binary fission is of the following four types,

i) Simple irregular binary fission

ii) Transverse binary fission

iii) Longitudinal binary fission

iv) Oblique binary fission

12. Which of the following statement is correct?

1. Simple irregular binary fission is seen in Virus
2. The contractile vacuoles cease to function and disappear
3. The nucleoli disintegrate and the nucleus divides mitotically
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Simple irregular binary fission is seen in Amoeba like irregular shaped organisms, where the plane of division is hard to observe. The contractile vacuoles cease to function and disappear. The nucleoli disintegrate and the nucleus divides mitotically. The cell then constricts in the middle, so the cytoplasm divides and forms two daughter cells.

13. In Paramecium the macronucleus divides by____ and the micronucleus divides by____

1. Mitosis, Amitosis
2. Amitosis, Mitosis
3. Meiosis, Mitosis
4. Meiosis, Amitosis

Explanation

In transverse binary fission, the plane of the division runs along the transverse axis of the individual. e.g. Paramecium and Planaria. In Paramecium the macronucleus divides by amitosis and the micronucleus divides by mitosis.

14. Which of the following statement is correct?

1. In longitudinal binary fission, the nucleus and the cytoplasm divides in the longitudinal axis of the organism
2. In flagellates, the flagellum is retained usually by one daughter cell.
3. The basal granule is divided into two and the new basal granule forms a flagellum in the other daughter individual
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

In longitudinal binary fission, the nucleus and the cytoplasm divides in the longitudinal axis of the organism. In flagellates, the flagellum is retained usually by one daughter cell. The basal granule is divided into two and the new basal granule forms a flagellum in the other daughter individual. e.g. Vorticella and Euglena.

15. Oblique binary fission is seen in______

1. Euglena
2. Ceratium
3. Vorticella
4. Paramecium

Explanation

In oblique binary fission the plane of division is oblique. It is seen in dinoflagellates. e.g. Ceratium.

16. Which of the following statement is correct?

1. In multiple fission the parent body divides into many similar daughter cells simultaneously
2. Each cytoplasmic part encircles one daughter nucleus
3. If multiple fission produces four or many daughter individuals by equal cell division and the young ones do not separate until the process is complete, then this division is called repeated fission.
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

In multiple fission the parent body divides into many similar daughter cells simultaneously. First, the nucleus divides repeatedly without the division of the cytoplasm, later the cytoplasm divides into as many parts as that of nuclei. Each cytoplasmic part encircles one daughter nucleus. This results in the formation of many smaller individuals from a single parent organism. If multiple fission produces four or many daughter individuals by equal cell division and the young ones do not separate until the process is complete, then this division is called repeated fission. e.g. Vorticella.

17. During unfavourable conditions Amoeba withdraws its pseudopodia and secretes a___ wall

1. Three layered
2. Two layered
3. Four layered
4. Five layered

Explanation

During unfavourable conditions (increase or decrease in temperature, scarcity of food) Amoeba withdraws its pseudopodia and secretes a three-layered, protective, chitinous cyst wall around it and becomes inactive. This phenomenon is called encystment.

18. Which of the following statement is correct?

1. In the process of strobilation, several transverse fissions occur simultaneously giving rise to a number of individuals
2. They often do not separate immediately from each other
3. Aurelia is an example of Strobilation
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

In the process of strobilation, several transverse fissions occur simultaneously giving rise to a number of individuals which often do not separate immediately from each other e.g. Aurelia.

19. __is the division of multinucleated parent into many multinucleate daughter individuals with the division of nuclei

1. Meiosis
2. Mitosis
3. Amitosis
4. Plasmotomy

Explanation

Plasmotomy is the division of multinucleated parent into many multinucleate daughter individuals with the division of nuclei. Nuclear division occurs later to maintain normal number of nuclei. Plasmotomy occurs in Opalina and Pelomyxa (Giant Amoeba).

20. During unfavourable conditions Amoeba multiplies by____ without encystment

1. Meiosis
2. Sporulation
3. Amitosis
4. Plasmotomy

Explanation

During unfavourable conditions Amoeba multiplies by sporulation without encystment. Nucleus breaks into several small fragments or chromatin blocks. Each fragment develops a nuclear membrane, becomes surrounded by cytoplasm and develops a spore-case around.

21. Which of the following statement is correct?

1. In budding, the parent body produces one or more buds and each bud grows into a young one.
2. The buds separate from the parent cannot lead a normal life
3. In sponges, the buds constrict and detach from the parent body and the bud develops into a new sponge
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

In budding, the parent body produces one or more buds and each bud grows into a young one. The buds separate from the parent to lead a normal life. In sponges, the buds constrict and detach from the parent body and the bud develops into a new sponge.

22. Exogenous budding is found in____

1. Paramecium
2. Euglena
3. Hydra
4. E. coli

Explanation

When buds are formed on the outer surface of the parent body, it is known as exogenous budding. e.g. Hydra

23. Which of the following statement about bud formation in Hydra is correct?

1. In Hydra when food is plenty, the ectoderm cells increase and form a small elevation on the body surface
2. Ectoderm and endoderm are pushed out to form the bud.
3. The bud contains an interior lumen in continuation with parent’s gastro-vascular cavity
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

In Hydra when food is plenty, the ectoderm cells increase and form a small elevation on the body surface. Ectoderm and endoderm are pushed out to form the bud. The bud contains an interior lumen in continuation with parent’s gastro-vascular cavity. The bud enlarges, develops a mouth and a circle of tentacles at its free end. When fully grown, the bud constricts at the base and finally separates from the parent body and leads an independent life.

24. Endogenous budding is found in___

1. Hydra
2. E. coli
3. Noctiluca
4. Euglena

Explanation

In Noctiluca, hundreds of buds are formed inside the cytoplasm and many remain within the body of the parent. This is called endogenous budding.

25. Which of the following statement is correct?

1. In freshwater sponges and in some marine sponges a regular and peculiar mode of asexual reproduction occurs by internal buds
2. It is known as Gemmules
3. A completely grown gemmule is a soft ball, consisting of an internal mass of food-laden archaeocytes
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

In freshwater sponges and in some marine sponges a regular and peculiar mode of asexual reproduction occurs by internal buds called gemmules is seen. A completely grown gemmule is a hard ball, consisting of an internal mass of food-laden archaeocytes. During unfavourable conditions, the sponge disintegrates but the gemmule can withstand adverse conditions. When conditions become favourable, the gemmules begin to hatch.

26. Which of the following statement is correct?

1. In fragmentation, the parent body breaks into fragments
2. Fragmentation or pedal laceration occurs in many genera of sea anemones.
3. Lobes are constricted off from the pedal disc and each of the lobe grows mesenteries and tentacles to form a new sea anemone
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

In fragmentation, the parent body breaks into fragments (pieces) and each of the fragment has the potential to develop into a new individual. Fragmentation or pedal laceration occurs in many genera of sea anemones. Lobes are constricted off from the pedal disc and each of the lobe grows mesenteries and tentacles to form a new sea anemone.

27. Which of the following statement is correct?

1. In the tapeworm, Taenia Solium the gravid (ripe) proglottids are the oldest at the posterior end of the strobila
2. The gravid proglottids are regularly cut off either singly or in groups from the posterior end by a process called apolysis
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

In the tapeworm, Taenia Solium the gravid (ripe) proglottids are the oldest at the posterior end of the strobila. The gravid proglottids are regularly cut off either singly or in groups from the posterior end by a process called apolysis.

28. Which of the following is the Secondary host of Tanium Solium?

1. Pig
2. Rat
3. Human
4. Snake

Explanation

In Taenia Solium, apolysis is very significant since it helps in transferring the developed embryos from the primary host (man) to find a secondary host (pig).

29. Regeneration was first studied in Hydra by____

1. Edwin
2. Abraham Trembley
3. Edward Jenner
4. Darwin

Explanation

Regeneration is regrowth in the injured region. Regeneration was first studied in Hydra by Abraham Trembley in 1740.

30. Morphallaxis type regeneration is found in___

1. Hydra
2. E. coli
3. Planaria
4. Both a and c

Explanation

Regeneration is of two types, morphallaxis and epimorphosis. In morphallaxis the whole body grows from a small fragment e.g. Hydra and Planaria. When Hydra is accidentally cut into several pieces, each piece can regenerate the lost parts and develop into a whole new individual.

31. Which of the following statement is correct?

1. Epimorphosis is the replacement of lost body parts.
2. It is of two types, namely reparative and restorative regeneration
3. In reparative regeneration, only certain damaged tissue can be regenerated
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Epimorphosis is the replacement of lost body parts. It is of two types, namely reparative and restorative regeneration. In reparative regeneration, only certain damaged tissue can be regenerated, e.g. human beings whereas in restorative regeneration severed body parts can develop. e.g. star fish, tail of wall lizard.

32. Which of the following statement about sexual reproduction is correct?

1. Sexual reproduction involves the fusion of male and female gametes
2. It results in the formation of Haploid zygote
3. This results in genetic variation
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Sexual reproduction involves the fusion of male and female gametes to form a diploid zygote, which develops into a new organism. It leads to genetic variation.

33. What are the types of sexual reproduction in animals?

1. Sporulation
2. Conjugation
3. Syngamy
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

The types of sexual reproduction seen in animals are syngamy (fertilization) and conjugation. In syngamy, the fusion of two haploid gametes takes place to produce a diploid zygote.

34. How many types of fertilization are there?

1. 2
2. 4
3. 3
4. 5

Explanation

Depending upon the place where the fertilization takes place, it is of two types: Internal fertilization and external fertilization.

35. Which of the following is not an example of external fertilization?

1. Sponges
2. Fishes
3. Reptiles
4. Amphibians

Explanation

Depending upon the place where the fertilization takes place, it is of two types. In external fertilization, the fusion of male and female gametes takes place outside the body of female organisms in the water medium. e.g. sponges, fishes and amphibians

36. Which of the following is not an example of Internal fertilization?

1. Reptiles
2. Fishes
3. Mammals
4. Aves

Explanation

In internal fertilization, the fusion of male and female gametes takes place within the body of female organisms. e.g. reptiles, Aves and mammals.

37. Which of the following statement is incorrect?

1. Sponge when macerated and squeezed through fine silk cloth, the cluster of cells pass through, and these can regenerate new sponges
2. This technique is used for cultivation of sponges.
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Sponge when macerated and squeezed through fine silk cloth, the cluster of cells pass through, and these can regenerate new sponges. This technique is used for cultivation of sponges.

38. Which of the following statement is correct?

1. The male and female gametes are produced by the same cell in Autogamy
2. Paramecium is an example of Autogamy
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

The male and female gametes are produced by the same cell or same organism and both the gametes fuse together to form a zygote. e.g. Actinosphaerium and Paramecium.

39. Which of the following statement is correct about Exogamy?

1. The male and female gametes are produced by different parents
2. It is uniparental
3. Male and female gametes fuse together to form zygote
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Exogamy- The male and female gametes are produced by different parents and they fuse to form a zygote. So, it is biparental. e.g. Human – dioecious or unisexual animal

40. Which of the following statement is correct?

1. In Hologamy, lower organisms, sometimes the entire mature organisms do not form gametes
2. They themselves behave as gametes
3. Trichonympha is an example of Hologamy
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Lower organisms, sometimes the entire mature organisms do not form gametes but they themselves behave as gametes and the fusion of such mature individuals is known as hologamy e.g. Trichonympha.

41. Paedogamy is the sexual union of young individuals produced immediately after the division of the adult parent cell by___

1. Meiosis
2. Mitosis
3. Amitosis
4. None

Explanation

Paedogamy- It is the sexual union of young individuals produced immediately after the division of the adult parent cell by mitosis.

42. Which of the following statement is incorrect?

1. Merogamy is the fusion of small sized and morphologically different gametes (merogametes) takes place
2. The fusion of morphological and physiological identical gametes (isogametes) is called isogamy
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Merogamy- The fusion of small sized and morphologically different gametes (merogametes) takes place

Isogamy- The fusion of morphological and physiological identical gametes (isogametes) is called isogamy. e.g. Monocystis.

43. Which of the following statement is correct?

1. The fusion of similar gametes is called anisogamy
2. Anisogamy occurs in higher animals but it is customary to use the term fertilization instead of anisogamy or syngamy
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

The fusion of dissimilar gametes is called anisogamy (Gr. An-without; iso-equal; gam-marriage). Anisogamy occurs in higher animals but it is customary to use the term fertilization instead of anisogamy or syngamy. e.g. higher invertebrates and all vertebrates.

44. Which of the following statement is correct?

1. Conjugation is the permanent union of the two individuals of the same species
2. During their union both individuals, called the conjugants exchange certain amount of nuclear material (DNA) and then get separated.
3. Paramecium is an example of conjugation
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Conjugation is the temporary union of the two individuals of the same species. During their union both individuals, called the conjugants exchange certain amount of nuclear material (DNA) and then get separated. Conjugation is common among ciliates, e.g. Paramecium, Vorticella and bacteria (Prokaryotes).

45. How phases of life cycle does organisms have?

1. 2
2. 4
3. 5
4. 3

Explanation

Phases of life cycle: Organisms have three phases – Juvenile phase, reproductive phase and senescent phase.

46. Which of the following statement is correct?

1. Juvenile phase/ vegetative phase is the period of growth between the birth of the individual up to reproductive maturity
2. During reproductive phase/ maturity phase the organisms reproduce and their off-springs reach maturity period
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Juvenile phase/ vegetative phase is the period of growth between the birth of the individual up-to reproductive maturity. During reproductive phase/ maturity phase the organisms reproduce and their off-springs reach maturity period.

47. Which of the following statement is correct?

1. On the basis of time, breeding animals are of two types
2. Seasonal breeders reproduce at particular period of the year such as frogs
3. Continuous breeders continue to breed throughout their sexual maturity
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

On the basis of time, breeding animals are of two types: seasonal breeders and continuous breeders. Seasonal breeders reproduce at particular period of the year such as frogs, lizards, most birds, deers etc., Continuous breeders continue to breed throughout their sexual maturity e.g. honey bees, poultry, rabbit etc

48. Senescent phase begins at the end of___

1. Juvenile phase
2. Reproductive phase
3. Both a and b
4. None

Explanation

Senescent phase begins at the end of reproductive phase when degeneration sets in the structure and functioning of the body.

49. Development of an egg into a complete individual without fertilization is known as___

1. Fertilization
2. Parthenogenesis
3. Oogensis
4. None

Explanation

Development of an egg into a complete individual without fertilization is known as parthenogenesis.

50. Which of the following statement is correct?

1. Parthenogenesis was first discovered by Charles Bonnet in 1745
2. Parthenogenesis is of two main types namely, Natural Parthenogenesis and Artificial Parthenogenesis.
3. In certain animals, parthenogenesis occurs regularly, constantly and naturally in their life cycle
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Parthenogenesis was first discovered by Charles Bonnet in 1745. Parthenogenesis is of two main types namely, Natural Parthenogenesis and Artificial Parthenogenesis. In certain animals, parthenogenesis occurs regularly, constantly and naturally in their life cycle and is known as natural parthenogenesis.

51. Which of the following is an example of Arrhenotoky?

1. Rat
2. Honey bee
3. Cow
4. Human

Explanation

Arrhenotoky: In this type only males are produced by parthenogenesis. e.g. honey bees

52. Which of the following is an example of Amphitoky?

1. Rat
2. Mice
3. Aphis
4. Spider

Explanation

Amphitoky: In this type parthenogenetic egg may develop into individuals of any sex. e.g. Aphis

53. Which of the following statement is correct?

1. Natural parthenogenesis may be of two types
2. Complete parthenogenesis is the only form of reproduction in certain animal
3. Incomplete parthenogenesis is found in some animals in which both sexual reproduction and parthenogenesis occurs
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Natural parthenogenesis may be of two types, viz., complete and incomplete. Complete parthenogenesis is the only form of reproduction in certain animals and there is no biparental sexual reproduction. There are no male organisms and so, such individuals are represented by females only. Incomplete parthenogenesis is found in some animals in which both sexual reproduction and parthenogenesis occurs.

54. In honeybees; fertilized eggs (zygotes) develop into____

1. Queen
2. Drones
3. Worker
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

In honeybees; fertilized eggs (zygotes) develop into queen and workers, whereas unfertilized eggs develop into drones (male). In paedogenetic parthenogenesis (paedogenesis) the larvae produce a new generation of larvae by parthenogenesis. It occurs in the sporocysts and Redia larvae of liver fluke. It is also seen in the larvae of some insects.

55. Which of the following are examples of Artificial parthenogenesis?

1. Mammals
2. Annelid
3. Seaurchin eggs
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

In artificial parthenogenesis, the unfertilized egg (ovum) is induced to develop into a complete individual by physical or chemical stimuli. e.g., Annelid and seaurchin eggs.

56. Which of these divide the somatic cells of single parent by amitotic or mitotic division?

a) Asexual reproduction

b) Blastogenic reproduction

c) Somatogenic reproduction

d) All the above

Explanation

Reproduction by a single parent without the involvement of gamete formation is asexual reproduction and the offspring produced are genetically identical. Asexual reproduction is usually by amitotic or mitotic division of the somatic (body) cells, hence is also known as somatogenic or blastogenic reproduction.

57. Which of the following fission is not seen in animals?

a) Binary fission

b) Plasmotomy

c) Alletropic

d) Sporulation

Explanation

Five types of fission are seen in animals. They are binary fission, multiple fission, plasmotomy, strobilation and sporulation.

58. Choose the Incorrect statements.

i) Depending upon the cells fertilization is of two types.

ii) Reptiles, Mammals and aves are related to the internal fetilzation.

iii) Fusion of male and female gametes takes place outside the body of female organisms in the water medium.

a) i only

b) ii only

c) iii only

d) All the above

Explanation

Depending upon the place where the fertilization takes place, it is of two types. In external fertilization, the fusion of male and female gametes takes place outside the body of female organisms in the water medium. e.g. sponges, fishes and amphibians. In internal fertilization, the fusion of male and female gametes takes place within the body of female organisms. e.g. reptiles, aves and mammals.

59. In which of these type only females are produced by parthenogenesis?

a) Arrhenotoky

b) Amphitoky

c) Thelytoky

d) None of the above

Explanation

Thelytoky: In this type only females are produced by parthenogenesis. e.g. Solenobia

60. Which of the following is not a main function of reproductive system?

a) To maintain the population of the species.

b) To produce hormones

c) Transport and sustain gametes

d) Nurture the developing offspring

Explanation

The reproductive system has four main functions namely, to produce the gametes namely sperms and ova, to transport and sustain these gametes, to nurture the developing offspring

and to produce hormones

61. Identify the Incorrect Match.

A. Insemination i) Transfer of sperms

B. Placentation ii) Expulsion of foetus

C. Gametogenesis iii) Formation of gametes

D. Implantation iv) Attachment of blastocyst

a) i only

b) ii only

c) iii only

d) iv only

Explanation

The major reproductive events in human beings are as follows:

Gametogenesis: Formation of gametes by spermatogenesis and oogenesis.

Insemination: Transfer of sperms by the male into the female genital tract.

Fertilization: Fusion of male and female gametes to form zygote, called Fertilization.

Cleavage: Rapid mitotic divisions of the zygote which convert the single celled zygote into a multicellular structure called blastocyst.

Implantation: Attachment of blastocyst to the uterine wall.

Placentation: Formation of placenta which is the intimate connection between foetus and uterine wall of the mother for exchange of nutrients.

62. Which of these process blastocyst is changed to gastrula?

a) Organogenesis

b) Implantation

c) Gastrulation

d) Placentation

Explanation

Gastrulation: Process by which blastocyst is changed into a gastrula with three primary germ layers.

63. Which of the following are formed by the Organogenesis process?

a) Specific tissues

b) Organ systems

c) Three germ layers

d) All the above

Explanation

Organogenesis: Formation of specific tissues, organs and organ systems from three germ layers.

64. Which of the following is not a function of hormones secreted by the pituitary gland?

a) Regulation of normal functioning of the reproductive system.

b) Development of the secondary sexual characteristics.

c) To maintain the functions of nervous systems.

d) Maturation of the reproductive system.

Explanation

Hormones secreted by the pituitary gland and the gonads help in the development of the secondary sexual characteristics, maturation of the reproductive system and regulation of normal functioning of the reproductive system.

65. Which of the following is the primary male sex organ?

a) Genitalia

b) Glands

c) Ducts

d) Testes

Explanation

The male reproductive system comprises of a pair of testes, accessory ducts, glands and

external genitalia. Testes are the primary male sex organs.

66. Choose the correct statements.

i) The female reproductive system is far more complex than the male.

ii) The female reproductive system consists of a pair of ovaries along with a pair of oviducts, uterus, cervix, vagina.

a) i only

b) ii only

c) Both i and ii

d) Neither i nor ii

Explanation

The female reproductive system is far more complex than the male because in addition to gamete formation, it has to nurture the developing foetus. The female reproductive system consists of a pair of ovaries along with a pair of oviducts, uterus, cervix, vagina and the external genitalia located in the pelvic region.

67. What are the process supported y the female reproduction system?

a) Fertilization

b) Process of ovulation

c) Child birth and child care.

d) All the above

Explanation

The female reproductive system parts along with the mammary glands are integrated structurally and functionally to support the process of ovulation, Fertilization, pregnancy, child birth and child care.

68. Which of the following plays a vital role in the process of gametogenesis?

a) Meiosis

b) Fusion

c) Mitosis

d) Fission

Explanation

Gametogenesis is the process of formation of gametes i.e., sperms and ovary from the primary sex organs in all sexually reproducing organisms. Meiosis plays the most significant role in the process of gametogenesis.

69. Which of the following is the smallest human cell?

a) Ovum

b) Sperm

c) Gametes

d) Zygote

Explanation

The sperm is the smallest human cell and the ovum or egg is the largest human cell.

70. Which of these are developed by the Oogenesis process in the ovaries?

a) Female gamete

b) Ovum

c) Egg

d) All the above

Explanation

Oogenesis is the process of development of the female gamete or ovum or egg in the ovaries. During foetal development, certain cells in the germinal epithelium of the foetal ovary divide by mitosis and produce millions of egg mother cells or oogonia.

71. Which is not a nature of the human ovum?

a) Non-cleidoic

b) Macroscopic

c) Alecithal

d) Microscopic

Explanation

Human ovum is non-cleidoic, alecithal and microscopic in nature. Its cytoplasm called ooplasm contains a large nucleus called the germinal vesicle

72. Choose the correct statements.

i) The menstrual or ovarian cycle occurs approximately once in every 28/29 days.

ii) The menstrual cycle of the female starts from menarche to menopause except during pregnancy.

a) i only

b) ii only

c) Both i and ii

d) Neither i nor ii

Explanation

The menstrual or ovarian cycle occurs approximately once in every 28/29 days during the reproductive life of the female from menarche (puberty) to menopause except during pregnancy.

73. Which of these phase is not related to menstrual cycle?

a) Follicular or proliferative

b) Oogenesis

c) Ovulatory phase

d) Luteal or secretory phase

Explanation

Menstrual cycle comprises of the following phases: Menstrual phase, Follicular or proliferative phase , Ovulatory phase and Luteal or secretory phase.

74. Choose the correct statements.

i) PCOS is a complex endocrine system disorder that affects women in their reproductive years.

ii) Polycystic means ‘many cysts’ refers to many partially formed follicles on the ovaries.

a) i only

b) ii only

c) Both i and ii

d) Neither i nor ii

Explanation

PCOS is a complex endocrine system disorder that affects women in their reproductive years. Polycystic means ‘many cysts’. It refers to many partially formed follicles on the ovaries, which contain an egg each. But they do not grow to maturity or produce eggs that can be fertilized.

75. What are the effects of PCOS in women?

a) Irregular menstrual cycles

b) Reduced fertility and increased risk of diabetes

c) Increased androgen levels

d) All the above

Explanation

Women with PCOS may experience irregular menstrual cycles, increased androgen levels, excessive facial or body hair growth (hirsutism), acne, obesity, reduced fertility and increased risk of diabetes. Treatment for PCOS includes a healthy lifestyle, weight loss and targeted hormone therapy.

76. Match.

A. Secondary amenorrhoea i) Menarche not appear till the age of 18

B. Primary amenorrhoea ii) Shorter menstrual cycle

C. Amenorrhoea iii) No menstruation for 3 consecutive months

D. Polymenorrhoea iv) Absence of menstruation

a) iii, i, iv, ii

b) i, ii, iv, iii

c) ii, iv, i, iii

d) iv, ii, iii, i

Explanation

Absence of menstruation is called amenorrhoea. If menarche does not appear till the age of 18, it is called primary amenorrhoea. Absence of menstruation for over three consecutive months is secondary amenorrhoea. Polymenorrhoea is a term used to describe a menstrual cycle that is shorter than 21 days.

12th Science Lesson 13 Questions in English

13] Reproductive Health

1. Assertion(A): Reproductive health is a community issue

Reason(R): Healthy people have healthier babies and are able to care for their family, and

contribute more to the society and community

1. Both (A) and (R) are correct, but (R) does not explain (A)
2. Both (A) and (R) are wrong

c)Both (A) and (R) are correct and (R) explains (A)

d) (A) is Correct and (R) is wrong

Explanation

Reproductive health represents a society with people having physically and functionally normal reproductive organs. Healthy people have healthier babies and are able to care for their family, and contribute more to the society and community. Hence, health is a community issue.

2. Reproductive system is a complex system controlled by the______ system

1. Exocrine
2. Endocrine
3. Neuronal
4. Neuro – Endocrine

Explanation

Reproductive system is a complex system controlled by the Neuro-endocrine system, hence, it is important to take necessary steps to protect it from infectious diseases and injury.

3. When did India introduced Family planning programme?

1. 1991
2. 1951
3. 1997
4. 1971

Explanation

India is amongst the first few countries in the world to initiate the ‘Family planning programme’ since 1951 and is periodically assessed every decade. These programmes are popularly named as ‘Reproductive and Child Health Care (RCH).

4. Which of the following are the tasks carried out under Family planning programme?

1. Creating awareness about care for pregnant women
2. Educating couples and those in the marriageable age groups about the available birth control methods and family planning norms
3. Introducing sex education in schools to provide information about adolescence
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Major tasks carried out under Family planning programmes are:

Creating awareness and providing medical assistance to build a healthy society.

Introducing sex education in schools to provide information about adolescence and adolescence related changes.

Educating couples and those in the marriageable age groups about the available birth control methods and family planning norms.

Creating awareness about care for pregnant women, post-natal care of mother and child and the importance of breast feeding.

Encouraging and supporting governmental and non-governmental agencies to identify new methods and/or to improve upon the existing methods of birth control.

5. Globally, about___ women die every day of preventable causes related to pregnancy and childbirth

1. 80
2. 800
3. 1000
4. 150

Explanation

Globally, about 800 women die every day of preventable causes related to pregnancy and childbirth; 20 per cent of these women are from India.

6. India’s infant mortality rate was____ per 1,000 live.

1. 70
2. 44
3. 100
4. 121

Explanation

India’s infant mortality rate was 44 per 1,000 live. Although, India has witnessed dramatic growth over the last two decades, maternal mortality still remains high as in comparison to many developing nations.

7. Which of the following are the maternity related health programme by government of India?

1. Janani Suraksha Yojana
2. Pradhan Mantri Jan dan Yojana
3. Pradhan Mantri Surakshit Matritva Abhiyan
4. RMNCH+A
5. 1, 2, 4
6. 2, 3, 4
7. 1, 3, 4
8. All the above

Explanation

Health care programmes such as massive child immunization, supply of nutritional food to the pregnant women, Janani Suraksha Yojana, Janani Shishu Suraksha Karyakaram, RMNCH+A approach (an integrated approach for reproductive, maternal, new born, child and adolescent health), Pradhan Mantri Surakshit Matritva Abhiyan, etc., are taken up at the national level by the Government of India.

8. What is the main reason for decreasing female ratio?

1. Skewed choice for male child
2. Hate towards female child
3. Love towards male child
4. All the above

Explanation

Due to small family norms and the skewed choice for a male child, female population is decreasing at an alarming rate.

9. Amniocentesis can be used for____

1. To detect chromosomal abnormality in foetus
2. Sex determination
3. Abortion of foetus
4. 1, 3
5. 2, 3
6. 1, 2
7. All the above

Explanation

Amniocentesis is a prenatal technique used to detect any chromosomal abnormalities in the foetus and it is being often misused to determine the sex of the foetus. Once the sex of the foetus is known, there may be a chance of female foeticide. Hence, a statutory ban on amniocentesis is imposed.

10. Which of the following statement is correct?

1. The sex ratio is the ratio of males to the females in a population
2. In India, the child sex ratio has decreased over the decade from 927 to 919 female for every 10000 males.
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

The sex ratio is the ratio of males to the females in a population. In India, the child sex ratio has decreased over the decade from 927 to 919 female for every 1000 males.

11. _____ is the manifestation of gender discrimination in our society

1. Female foeticide
2. Female infanticide
3. Both a and b
4. None

Explanation

To correct this ratio, steps are needed to change the mind set and attitudes of people, especially in the young adults. Female foeticide and infanticide is the manifestation of gender discrimination in our society.

12. Which of the following statement is incorrect?

1. Female foeticide refers to ‘aborting the female in the mother’s womb
2. Female infanticide is ‘killing the female child after her birth’
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Female foeticide refers to ‘aborting the female in the mother’s womb’; whereas female infanticide is ‘killing the female child after her birth’. These have resulted in imbalance in sex ratio.

13. What is the rank of India in UNDP’s GII 2018?

1. 100
2. 97
3. 135
4. 89

Explanation

In UNDP’s GII 2018 (United nations developmental programmes gender inequality index) reflected that India was ranked at 135 out of 187 countries due to availability of very few economic opportunities to women as compared to men.

14. When was PCPNDT Act enacted?

1. 1993
2. 1994
3. 1999
4. 2001

Explanation

In order to prevent female foeticide and infanticide, Government of India has taken various steps like PCPNDT Act (Preconception and Prenatal diagnostic technique act-1994) enacted to ban the identification of sex and to prevent the use of prenatal diagnostic techniques for selective abortion.

15. Which of the following are the measures taken by Government to ensure better life for girl child?

1. Entrepreneurship programmes
2. POCSO Act
3. Sexual harassment at workplace (Prevention, prohibition and redressal) Act
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Various measures are taken by the Government to ensure survival, provision of better nutrition, education, protection and empowerment of girls by eliminating the differences in the sex ratio, infant mortality rate and improving their nutritional and educational status. POCSO Act (Prevention of children from sexual offences), Sexual harassment at workplace (Prevention, prohibition and redressal) Act.

16. On which committees recommendation changes were made in criminal law for creating a safe and secure environment for both females and males?

1. Swaran Singh Committee
2. Justice Verma committee
3. Sarkaria commission
4. Rajmannar committee

Explanation

Changes in the Criminal law based on the recommendations of Justice Verma Committee, 2013 aims at creating a safe and secure environment for both females and males.

17. Which of the following statement is correct?

1. Increased health facilities and better living conditions have enhanced longevity
2. According to a recent report from the UN, India’s population has already reached 1.26 billion
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Increased health facilities and better living conditions have enhanced longevity. According to a recent report from the UN, India’s population has already reached 1.26 billion.

18. When is India expected to surpass China’s population?

1. 2025
2. 2022
3. 2021
4. 2030

Explanation

India is expected to become the largest country in population size, surpassing China around 2022. To overcome the problem of population explosion, birth control is the only available solution.

19. Which advertisement was made by TN government regarding population control measure?

1. Naam iruvar namakku iruvar
2. Naam iruvar namakku oruvar
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

People should be motivated to have smaller families by using various contraceptive devices. Advertisements by the Government in the media as well as posters/bills, etc., with a slogan Naam iruvar namakku iruvar (we two, ours two) and Naam iruvar namakku oruvar (we two, ours one) have also motivated to control population growth in Tamil Nadu.

20. Statutory rising of marriageable age of the female to___ years and that of males to__ years

1. 20, 21
2. 18, 21
3. 19, 22
4. 22, 24

Explanation

Statutory rising of marriageable age of the female to 18 years and that of males to 21 years and incentives given to couples with small families are the other measures taken to control population growth in our country.

21. Which of the following statement is correct?

1. The voluntary use of contraceptive procedures to prevent fertilization or prevent implantation of a fertilized egg in the uterus is termed as birth control
2. An ideal contraceptive should be user friendly, easily available, with least side effects and should not interfere with sexual drive
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

The voluntary use of contraceptive procedures to prevent fertilization or prevent implantation of a fertilized egg in the uterus is termed as birth control. An ideal contraceptive should be user friendly, easily available, with least side effects and should not interfere with sexual drive.

22. The contraceptive methods is/are of___ types

1. 2
2. 3
3. 4
4. 5

Explanation

The contraceptive methods are of two types – temporary and permanent. Natural, chemical, mechanical and hormonal barrier methods are the temporary birth control methods.

23. Which of the following statement is incorrect?

1. Natural method is used to prevent meeting of sperm with ovum
2. Rhythm method (safe period), coitus interruptus, continuous abstinence and lactational amenorrhoea are natural method
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Natural method is used to prevent meeting of sperm with ovum. i.e., Rhythm method (safe period), coitus interruptus, continuous abstinence and lactational amenorrhoea.

24. Ovulation occurs at about the___ day of the menstrual cycle

1. 12^th
2. 5^th
3. 14^th
4. 20^th

Explanation

Periodic abstinence/rhythm method is a natural method of birth control. Ovulation occurs at about the 14th day of the menstrual cycle.

25. Sperm remains alive for about___ hours in the female reproductive tract

1. 10
2. 48
3. 24
4. 72

Explanation

Ovum survives for about two days and sperm remains alive for about 72 hours in the female reproductive tract. Coitus is to be avoided during this time.

26. _____ is the simplest and most reliable way to avoid pregnancy

1. Periodic abstinence
2. Continuous abstinence
3. Lactational amenorrhoea
4. Coitus interruptus

Explanation

Continuous abstinence is the simplest and most reliable way to avoid pregnancy is not to have coitus for a defined period that facilitates conception.

27. ____ is the oldest family planning method

1. Periodic abstinence
2. Continuous abstinence
3. Lactational amenorrhoea
4. Coitus interruptus

Explanation

Coitus interruptus is the oldest family planning method. The male partner withdraws his penis before ejaculation, thereby preventing deposition of semen into the vagina.

28. Menstrual cycles resume as early as___ weeks from parturition

1. 10 to 12
2. 6 to 8
3. 4 to 5
4. 2 to 4

Explanation

Menstrual cycles resume as early as 6 to 8 weeks from parturition. However, the reappearance of normal ovarian cycles may be delayed for six months during breastfeeding. This delay in ovarian cycles is called lactational amenorrhoea.

29. Which of the following statement is correct?

1. Lactational amenorrhoea serves as a natural, but an unreliable form of birth control.
2. Suckling by the baby during breast-feeding stimulates the pituitary to secrete increased Vasopressin hormone in order to increase milk production
3. This high prolactin concentration in the mother’s blood may prevent menstrual cycle by suppressing the release of GnRH
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Lactational amenorrhoea serves as a natural, but an unreliable form of birth control. Suckling by the baby during breast-feeding stimulates the pituitary to secrete increased prolactin hormone in order to increase milk production. This high prolactin concentration in the mother’s blood may prevent menstrual cycle by suppressing the release of GnRH (Gonadotropin Releasing Hormone) from hypothalamus and gonadotropin secretion from the pituitary.

30. Which of the following statement is correct about barrier method is correct?

1. Ovum and Sperm are prevented from meeting
2. Fertilization occurs
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Barrier methods: In these methods, the ovum and sperm are prevented from meeting so that fertilization does not occur.

31. Which of the following are used as chemical barrier in birth control?

1. Foaming tablets
2. Jellies
3. Melting suppositories
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Chemical barrier: Foaming tablets, melting suppositories, jellies and creams are used as chemical agents that inactivate the sperms in the vagina.

32. Which of the following statement is correct?

1. Condoms are a thin sheath used to cover the penis in male
2. Condom also safeguards the user from AIDS and STDs
3. Condoms are made of polyurethane, latex and lambskin
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Mechanical barrier: Condoms are a thin sheath used to cover the penis in male whereas in female it is used to cover vagina and cervix just before coitus so as to prevent the entry of ejaculated semen into the female reproductive tract. This can prevent conception. Condoms should be discarded after a single use. Condom also safeguards the user from AIDS and STDs. Condoms are made of polyurethane, latex and lambskin

33. Diaphragms, cervical caps and vaults are used by___

1. Male
2. Female
3. Transgender
4. None

Explanation

Diaphragms, cervical caps and vaults are made of rubber and are inserted into the female reproductive tract to cover the cervix before coitus in order to prevent the sperms from entering the uterus.

34. Which of the following statement is correct?

1. Pills are used to prevent ovulation by inhibiting the secretion of FSH and LH hormones
2. It contains synthetic progesterone and Estrogen hormones
3. Saheli, contraceptive pill by Central Drug Research Institute (CDRI) in Lucknow, India contains a non-steroidal preparation called Centchroman.
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Pills are used to prevent ovulation by inhibiting the secretion of FSH and LH hormones. A combined pill is the most commonly used birth control pill. It contains synthetic progesterone and estrogen hormones. Saheli, contraceptive pill by Central Drug Research Institute (CDRI) in Lucknow, India contains a non-steroidal preparation called Centchroman.

35. Intrauterine Devices has a success rate of___ %

1. 90 to 99
2. 95 to 99
3. 80 to 85
4. 70 to 75

Explanation

Intrauterine Devices (IUDs) is one of the popular methods of contraception in India and has a success rate of 95 to 99%.

36. Which of the following statement is correct?

1. Intrauterine devices are inserted by medical experts in the uterus through the vagina
2. These devices are available as copper releasing IUDs, hormone releasing IUDs and non-medicated IUD
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Intrauterine devices are inserted by medical experts in the uterus through the vagina. These devices are available as copper releasing IUDs, hormone releasing IUDs and non-medicated IUDs. IUDs increase phagocytosis of sperm within the uterus. IUDs are the ideal contraceptives for females who want to delay pregnancy.

37. Which of the following statement is correct?

1. Copper releasing IUDs differ from each other by the amount of copper
2. IUDs such as Cu T-380 A, Nova T, Cu 7, Cu T 380 Ag, Multiload 375, etc. release free copper and copper salts into the uterus and suppress sperm motility
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Copper releasing IUDs differ from each other by the amount of copper. Copper IUDs such as Cu T-380 A, Nova T, Cu 7, Cu T 380 Ag, Multiload 375, etc. release free copper and copper salts into the uterus and suppress sperm motility. They can remain in the uterus for five to ten years.

38. Which of the following statement is incorrect?

1. Hormone-releasing IUDs such as Progestasert and LNG – 20 are often called as intrauterine systems
2. They increase the viscosity of the cervical mucus and thereby prevent sperms from entering the cervix
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Hormone-releasing IUDs such as Progestasert and LNG – 20 are often called as intrauterine systems (IUS). They increase the viscosity of the cervical mucus and thereby prevent sperms from entering the cervix. Non-medicated IUDs are made of plastic or stainless steel. Lippes loop is a double S-shaped plastic device.

39. Which of the following statement is correct?

1. Surgical sterilisation methods are the permanent contraception methods advised for male and female partners to prevent any more pregnancies
2. It blocks the transport of the gametes and prevents conception
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Permanent birth control methods are adopted by the individuals who do not want to have any more children. Surgical sterilisation methods are the permanent contraception methods advised for male and female partners to prevent any more pregnancies. It blocks the transport of the gametes and prevents conception.

40. Tubectomy is the surgical sterilisation in____

1. Male
2. Female
3. Transgender
4. None

Explanation

Tubectomy is the surgical sterilisation in women. In this procedure, a small portion of both fallopian tubes are cut and tied up through a small incision in the abdomen or through vagina. This prevents fertilization as well as the entry of the egg into the uterus.

41. Vasectomy is the surgical procedure for___ sterilisation

1. Male
2. Female
3. Transgender
4. None

Explanation

Vasectomy is the surgical procedure for male sterilisation. In this procedure, both vas deferens are cut and tied through a small incision on the scrotum to prevent the entry of sperm into the urethra. Vasectomy prevents sperm from heading off to penis as the discharge has no sperms in it.

42. Early medical termination of child is extremely safe up-to____

1. 2 weeks
2. 12 weeks
3. 36 weeks
4. 8 weeks

Explanation

Medical method of abortion is a voluntary or intentional termination of pregnancy in a non-surgical or non-invasive way. Early medical termination is extremely safe up to 12 weeks (the first trimester) of pregnancy and generally has no impact on a women’s fertility.

43. Government of India legalized MTP in____

1. 1991
2. 1971
3. 1981
4. 1999

Explanation

Government of India legalized MTP in 1971 for medical necessity and social consequences with certain restrictions like sex discrimination and illegal female foeticides to avoid its misuse. MTP performed illegally by unqualified quacks is unsafe and could be fatal. MTP of the first conception may have serious psychological consequences

44. Abortion during the _____ trimester is more risky

1. 2^nd
2. 3^rd
3. 1^st
4. 4^th

Explanation

Abortion during the second trimester is more- risky as the foetus becomes intimately associated with the maternal tissue.

45. Which of the following statement is incorrect?

1. Sexually transmitted diseases (STD) or Venereal diseases (VD) or Reproductive tract infections (RTI) are called as Sexually transmitted infections
2. Normally STI are transmitted from person to person during intimate sexual contact with an infected partner
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Sexually transmitted diseases (STD) or Venereal diseases (VD) or Reproductive tract infections (RTI) are called as Sexually transmitted infections (STI). Normally STI are transmitted from person to person during intimate sexual contact with an infected partner.

46. Which of the following are STI?

1. Thalasemia
2. HIV
3. Hepatitis- B
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Infections like Hepatitis-B and HIV are transmitted sexually as well as by sharing of infusion needles, surgical instruments, etc with infected people, blood transfusion or from infected mother to baby.

47. People in the age of__ to __ years are prone to these sexual infections

1. 10, 20
2. 20, 25
3. 15, 24
4. 30, 35

Explanation
People in the age of 15 to 24 years are prone to these infections. The bacterial STI are gonorrhoea, syphilis, chancroid, chlamydiasis and lymphogranuloma venereum. The viral STI are genital herpes, genital warts, Hepatitis-B and AIDS.

48. Ways to prevent STD?

1. Avoid sex with unknown partner/ multiple partners
2. Use condoms
3. In case of doubt, consult a doctor for diagnosis and get complete treatment
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Prevention of STDs:

a. Avoid sex with unknown partner/ multiple partners.

b. Use condoms.

c. In case of doubt, consult a doctor for diagnosis and get complete treatment.

49. India has the____ largest HIV epidemic in the world

1. 1^st
2. 2^nd
3. 4^th
4. 3^rd

Explanation

According to World Health Organization (WHO), 2017 more than one million people globally acquires a sexually transmitted infection every day. India has the third largest HIV epidemic in the world, with 2.1 million people living with HIV

50. _____ unit of Health and family welfare department of the Government of Tamil Nadu does free screening for cervical and breast cancer.

1. TNHSP
2. DPH
3. DMS
4. DME

Explanation

TNHSP (Tamil Nadu health systems project), a unit of the Health and family welfare department of the Government of Tamil Nadu does free screening for cervical and breast cancer.

51. Which of the following body parts are affected by Gonorrhoea?

1. Throat
2. Rectum
3. Cervix
4. All the above

Explanation

52. What is the incubation period of Syphilis?

1. 2 to 5 days
2. 30 to 40 days
3. 10 to 90 days
4. 80 to 90 days

Explanation

53. Which of the following are the symptoms of Genital herpes?

1. Dysentery
2. Pain during urination, bleeding between periods
3. Swelling in the groin nodes
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

54. Which of the following are symptoms of Hepatitis-B?

1. Fatigue
2. Fever
3. Liver cirrhosis
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

55. Which of the following are the symptoms of Candidiasis?

1. Attacks mouth
2. Attacks vagina
3. Abnormal vaginal discharge
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

56. What is the incubation period for Trichomoniasis?

1. 2 to 5 days
2. 2 to 5 weeks
3. 4 to 28 days
4. 4 to 5 days

Explanation

57. Cervical cancer is caused by a_____

1. Sexually transmitted virus
2. Sexually transmitted bacteria
3. Sexually transmitted fungi
4. Abnormal cell growth in cervix cells

Explanation

Cervical cancer is caused by a sexually transmitted virus called Human Papilloma virus (HPV). HPV may cause abnormal growth of cervical cells or cervical dysplasia.

58. Which of the following are the common symptoms of cervical cancer?

1. Pelvic pain
2. Abnormal vaginal bleeding
3. Increased vaginal discharge
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

The most common symptoms and signs of cervical cancer are pelvic pain, increased vaginal discharge and abnormal vaginal bleeding. The risk factors for cervical cancer include 1. Having multiple sexual partners 2. Prolonged use of contraceptive pills.

59. Which of the following statement is correct?

1. Cervical cancer can be diagnosed by a Papanicolaou smear (PAP smear) combined with an HPV test
2. X-Ray, CT scan, MRI and a PET scan may also be used to determine the stage of cancer
3. The treatment options for cervical cancer include radiation therapy, surgery and chemotherapy.
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Cervical cancer can be diagnosed by a Papanicolaou smear (PAP smear) combined with an HPV test. X-Ray, CT scan, MRI and a PET scan may also be used to determine the stage of cancer. The treatment options for cervical cancer include radiation therapy, surgery and chemotherapy.

60. Screening for cervical cancer is recommended for women above__ years once in a year

1. 18
2. 25
3. 30
4. 50

Explanation

Modern screening techniques can detect precancerous changes in the cervix. Therefore, screening is recommended for women above 30 years once in a year.

61. Which of the following statement is correct?

1. Cervical cancer can be prevented with vaccination
2. Primary prevention begins with HPV vaccination of girls aged 19 – 30 years
3. Modification in lifestyle can also help in preventing cervical cancer
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Primary prevention begins with HPV vaccination of girls aged 9 – 13 years, before they become sexually active. Modification in lifestyle can also help in preventing cervical cancer. Healthy diet, avoiding tobacco usage, preventing early marriages, practicing monogamy and regular exercise minimize the risk of cervical cancer.

62. Which of the following statement is incorrect?

1. Inability to conceive or produce children even after unprotected sexual cohabitation is called infertility
2. Inability of a man to produce sufficient numbers or quality of sperm to impregnate a woman or inability of a woman to become pregnant or maintain a pregnancy
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Inability to conceive or produce children even after unprotected sexual cohabitation is called infertility. That is, the inability of a man to produce sufficient numbers or quality of sperm to impregnate a woman or inability of a woman to become pregnant or maintain a pregnancy.

63. Which of the following statement is correct?

1. The causes for infertility are tumours formed in the pituitary or reproductive organs, inherited mutations of genes responsible for the biosynthesis of sex hormones, malformation of the cervix or fallopian tubes and inadequate nutrition before adulthood
2. Long-term stress damages many aspects of health especially the menstrual cycle
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

The causes for infertility are tumours formed in the pituitary or reproductive organs, inherited mutations of genes responsible for the biosynthesis of sex hormones, malformation of the cervix or fallopian tubes and inadequate nutrition before adulthood. Long-term stress damages many aspects of health especially the menstrual cycle. Ingestion of toxins (heavy metal cadmium), heavy use of alcohol, tobacco and marijuana, injuries to the gonads and aging also cause infertility.

64. Which of the following are the causes of infertility?

1. Pelvic inflammatory disease (PID), uterine fibroids and endometriosis are the most common causes of infertility in women
2. Tight clothing in men may raise the temperature in the scrotum and affect sperm production
3. Tight clothing in men may raise the temperature in the scrotum and affect sperm production
4. Males may develop an autoimmune response to their own sperm
5. 1, 2, 3
6. 1, 2, 4
7. 2, 3, 4
8. All the above

Explanation

Other causes of infertility

Pelvic inflammatory disease (PID), uterine fibroids and endometriosis are the most common causes of infertility in women.

Low body fat or anorexia in women. i.e. a psychiatric eating disorder characterised by the fear of gaining weight.

Undescended testes and swollen veins (varicocoele) in scrotum.

Tight clothing in men may raise the temperature in the scrotum and affect sperm production.

Under developed ovaries or testes.

Female may develop antibodies against her partner’s sperm.

Males may develop an autoimmune response to their own sperm.

65. Women born with ovaries with uterus which is not functional is called as____

1. HIV
2. Parkinson’s syndrome
3. Mayer-Rokitansky syndrome
4. None

Explanation

All women are born with ovaries, but some do not have functional uterus. This condition is called Mayer-Rokitansky syndrome.

66. Which of the following statement is correct?

1. A collection of procedures, which includes the handling of gametes and/or embryos outside the body to achieve pregnancy is known as Assisted Reproductive Technology
2. It increases the chance of pregnancy in infertile couples
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

A collection of procedures, which includes the handling of gametes and/or embryos outside the body to achieve pregnancy is known as Assisted Reproductive Technology. It increases the chance of pregnancy in infertile couples. ART includes intra-uterine insemination (IUI), in vitro fertilization, (IVF) Embryo transfer (ET), Zygote intra-fallopian transfer (ZIFT), Gamete intrafallopian transfer (GIFT), Intra-cytoplasmic sperm injection (ICSI), Preimplantation genetic diagnosis, oocyte and sperm donation and surrogacy.

67. Which of the following statement is correct?

1. In vitro fertilization, sperm and eggs are allowed to unite outside the body in a laboratory
2. Initially, IVF was used to treat women with blocked, damaged, or absent fallopian tubes
3. Today, IVF is used to treat many causes of infertility
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

In vitro fertilization (IVF) or Test tube baby is technique, sperm and eggs are allowed to unite outside the body in a laboratory. One or more fertilized eggs may be transferred into the woman’s uterus, where they may implant in the uterine lining and develop. Excess embryos may be cryopreserved (frozen) for future use. Initially, IVF was used to treat women with blocked, damaged, or absent fallopian tubes. Today, IVF is used to treat many causes of infertility. The basic steps in an IVF treatment cycle are ovarian stimulation, egg retrieval, fertilization, embryo culture, and embryo transfer.

68. Which of the following statement about Intra-uterine insemination is correct?

1. This is a procedure to treat infertile men with low sperm count
2. The semen is collected either from the husband or from a healthy donor and is introduced into the uterus through the vagina by a catheter after stimulating the ovaries to produce more ova
3. The sperms swim towards the fallopian tubes to fertilize the egg, resulting in normal pregnancy
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Intra-uterine insemination (IUI):

This is a procedure to treat infertile men with low sperm count. The semen is collected either from the husband or from a healthy donor and is introduced into the uterus through the vagina by a catheter after stimulating the ovaries to produce more ova. The sperms swim towards the fallopian tubes to fertilize the egg, resulting in normal pregnancy.

69. Which of the following statement is correct?

1. Cryopreservation (or freezing) of embryos is often used when there are more embryos than needed for a single IVF transfer.
2. Embryo cryopreservation can provide an additional opportunity for pregnancy, through a Frozen embryo transfer (FET), without undergoing another ovarian stimulation and retrieval
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

70. As in IVF, the zygote up to___ blastomere stage is transferred to the fallopian tube by laparoscopy

1. 3
2. 4
3. 8
4. 16

Explanation

As in IVF, the zygote up to 8 blastomere stage is transferred to the fallopian tube by laparoscopy. The zygote continues its natural divisions and migrates towards the uterus where it gets implanted.

71. Which of the following statement about Gamete intra-fallopian transfer is correct?

1. Transfer of an ovum collected from a donor into the fallopian tube
2. In this the eggs are collected from the ovaries and placed with the sperms in one of the fallopian tubes
3. The zygote travels toward the uterus and gets implanted in the inner lining of the uterus.
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Gamete intra-fallopian transfer (GIFT):

Transfer of an ovum collected from a donor into the fallopian tube. In this the eggs are collected from the ovaries and placed with the sperms in one of the fallopian tubes. The zygote travels toward the uterus and gets implanted in the inner lining of the uterus.

72. Which of the following statement is incorrect?

1. Surrogacy is a method of assisted reproduction or agreement whereby a woman agrees to carry a pregnancy for another person
2. Through in vitro fertilization (IVF), embryos are created in a lab and are transferred into the surrogate mother’s uterus.
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

Surrogacy is a method of assisted reproduction or agreement whereby a woman agrees to carry a pregnancy for another person, who will become the new born child’s parent after birth. Through in vitro fertilization (IVF), embryos are created in a lab and are transferred into the surrogate mother’s uterus.

73. Azoospermia is observed approximately in____ % of the population

1. 4
2. 2
3. 3
4. 1

Explanation

Azoospermia is defined as the absence of spermatozoa in the ejaculate semen on atleast two occasions and is observed approximately in 1% of the population.

74. Which of the following statement is correct?

1. Ultrasound has no known risks other than mild discomfort due to pressure from the transducer on the abdomen or vagina.
2. Mild radiation is used during this procedure
3. Ultrasonography is usually performed in the first trimester for dating, determination of the number of foetuses, and for assessment of early pregnancy complications
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Ultrasound has no known risks other than mild discomfort due to pressure from the transducer on the abdomen or vagina. No radiation is used during this procedure. Ultrasonography is usually performed in the first trimester for dating, determination of the number of foetuses, and for assessment of early pregnancy complications.

75. Which of the following statement is correct?

1. Most common type, the 2-D ultrasound provides a flat picture of one aspect of the baby
2. The latest technology is 4-D ultrasound, which allows the health care provider to visualize the unborn baby moving in real time with a three-dimensional image
3. 1 alone
4. 2 alone
5. 1, 2
6. None

Explanation

There are several types of ultrasound imaging techniques. As the most common type, the 2-D ultrasound provides a flat picture of one aspect of the baby. The 3-D image allows the health care provider to see the width, height and depth of the images, which can be helpful during the diagnosis. The latest technology is 4-D ultrasound, which allows the health care provider to visualize the unborn baby moving in real time with a three-dimensional image.

76. Which of the following statement is correct?

1. Amniocentesis involves taking a small sample of the amniotic fluid that surrounds the foetus to diagnose for chromosomal abnormalities
2. Amniocentesis is generally performed in a pregnant woman between the 15th and 20th weeks of pregnancy by inserting a long, thin needle through the abdomen into the amniotic sac to withdraw a small sample of amniotic fluid.
3. The amniotic fluid contains cells shed from the foetus.
4. 1, 2
5. 1, 3
6. 2, 3
7. All the above

Explanation

Amniocentesis involves taking a small sample of the amniotic fluid that surrounds the foetus to diagnose for chromosomal abnormalities. Amniocentesis is generally performed in a pregnant woman between the 15th and 20th weeks of pregnancy by inserting a long, thin needle through the abdomen into the amniotic sac to withdraw a small sample of amniotic fluid. The amniotic fluid contains cells shed from the foetus

77. The average foetal heart rate is between____ and___ beats per minute.

1. 80, 120
2. 100, 120
3. 60 to 80
4. 120, 160

Explanation

Foetoscope is used to monitor the foetal heart rate and other functions during late pregnancy and labour. The average foetal heart rate is between 120 and 160 beats per minute. An abnormal foetal heart rate or pattern may mean that the foetus is not getting enough oxygen and it indicates other problems.

78. ____ is known as anti-sterility vitamin

1. D
2. E
3. A
4. B12

Explanation

Vitamin E is known as anti-sterility vitamin as it helps in the normal functioning of reproductive structures. Vitamin E is known as anti-sterility vitamin as it helps in the normal functioning of reproductive structures.

79. ____ is observed as World Population Day.

1. June 13
2. July 13
3. Jun 11
4. July 11

Explanation

11th July is observed as the World Population Day. 1st December is observed as World AIDS Day.

80. NACO (National AIDS Control Organisation) was established in____

1. 1992
2. 1980
3. 2003
4. 2001

Explanation

NACO (National AIDS Control Organisation) was established in 1992. Syphilis and gonorrhoea are commonly called as international diseases.

81. According to the 2017 WHO reports India is the ___ largest HIV epidemic in the world.

a) 3^rd

b) 7^th

c) 4^th

d) 2^nd

Explanation

According to World Health Organization (WHO), 2017 more than one million people globally acquires a sexually transmitted infection every day. India has the third largest HIV epidemic in the world, with 2.1 million people living with HIV.

82. Which of these are used to diagnosed the cervical cancer?

a) Papanicolaou smear with an HPV

b) X-ray

c) Normal Blood tests

d) PET scan

Explanation

Cervical cancer can be diagnosed by a Papanicolaou smear (PAP smear) combined with an HPV test. X-Ray, CT scan, MRI and a PET scan may also be used to determine the stage of cancer.

The treatment options for cervical cancer include radiation therapy, surgery and chemotherapy.

83. Choose the correct statements.

i) Cervical cancer can be prevented with vaccination.

ii) Primary prevention begins with HPV vaccination of girls aged 9 – 13 years.

iii) Modification in lifestyle can also help in preventing cervical cancer.

a) i only

b) ii only

c) iii only

d) All the above

Explanation

Cervical cancer can be prevented with vaccination. Primary prevention begins with HPV vaccination of girls aged 9 – 13 years, before they become sexually active. Modification in lifestyle can also help in preventing cervical cancer. Healthy diet, avoiding tobacco usage, preventing early marriages, practicing monogamy and regular exercise minimize the risk of cervical cancer

84. What is the condition of the Mayer-Rokitansky syndrome?

a) Women born non functional uterus.

b) Menarche does not appear till the age of 18.

c) Excessive facial or body hair growth

d) Absence of menstruation

Explanation

All women are born with ovaries, but some do not have functional uterus. This condition is called Mayer-Rokitansky syndrome.

85. Identify the Incorrect Match.

A. 2-D ultrasound i) Flat picture of one aspect

B. 3-D ultrasound ii) See the width, height and depth of the images

C. 4-D ultrasound iii) Visualize the unborn baby movement

a) i only

b) ii only

c) iii only

d) None of the above

Explanation

There are several types of ultrasound imaging techniques. As the most common type, the 2-D ultrasound provides a flat picture of one aspect of the baby. The 3-D image allows the health care provider to see the width, height and depth of the images, which can be helpful during the diagnosis. The latest technology is 4-D ultrasound, which allows the health care provider to visualize the unborn baby moving in real time with a three-dimensional image.