Electricity Online Test 8th Science Lesson 10 Questions in English

1. Who among the following scientist considered that atoms cannot be divided further?

2. Movement of which particle in a material constitutes electric current and generates an energy called electric energy or electricity?

3. Which among the following is not the sub atomic particle?

4. Which among the following are found inside the nucleus which is at the centre of an atom?

5. In an atom, the number of protons is equal to number of what?

6. Which among the following statement is correct

1) Charge or electric charge is the basic property of matter that causes objects to attract or
repel each other. It is carried by the subatomic particles like protons and electrons. Charges
can be created and destroyed as well.

2) There are two types of charges: positive charge and negative charge. Protons carry positive
charge and the electrons carry negative charge. There is a force of attraction or repulsion
between the charges. Unlike charges attract each other and like charges repel each other.

7. Electric charge is measured in what?

8. Small amount of charge that can exist freely is called _____

9. Which among the following is the value of elementary charge (e)?

10. Electrons in which orbit can be easily removed from the atom?

11. By which among the following way transfer of charge does not take place?

12. Which among the following statement is correct regarding transfer of charges by friction?

1) Comb rubbed with hair gains electrons from the hair and becomes negatively charged. These electrons are accumulated on the surface of the comb. When a piece of paper is teared into bits, positive and negative charges are present at the edges of the bits. Negative charges in the comb attract positive charges in the bits. So, the paper bits are moving towards the comb.

2) While combing hair charges are transferred from the hair to comb due to friction. If the hair is wet, the friction between the hair and the comb increases which will reduce the number of electrons transferring from hair to comb. Hence, rubbing certain materials with one another can cause the build-up of electrical charges on the surfaces. From this it is clear that charges are transferred by friction.

13. Which among the following statement is correct

1) When a glass rod is rubbed with a silk cloth the free electrons in the glass rod are transferred to silk cloth. It is because the free electrons in the glass rod are less tightly bound as compared to that in silk cloth. Since the glass rod loses electrons, it has a deficiency of electrons and hence acquires positive charge. But the silk cloth has excess of electrons. So, it becomes negatively charged.

2) When an ebonite rod (rod made by vulcanized rubber) is rubbed with fur, the fur transfers electrons to the ebonite rod because the electrons in the outermost orbit of the atoms in fur are loosely bound as compared to the ebonite rod. The ebonite rod which has excess electrons becomes negatively charged and the fur which has deficiency of electrons is positively charged.

14. When neutral object can become positively charged?

15. Which among the following statement is correct regarding transfer of charges by conduction

1) Take a sheet of paper. Turn it into a hollow cylinder. Tie one end of the cylinder with a silk thread and hang it from a stand. Now take an ebonite rod and charge it by rubbing it with a woollen cloth. Bring this charged ebonite rod near the paper cylinder. The cylinder will be attracted by the rod. If you touch the paper cylinder by the charged rod, you will see the paper cylinder repelling the rod.

2) When the ebonite rod is rubbed with woollen cloth, electrons from the woollen cloth are transferred to the ebonite rod. Now ebonite rod will be negatively charged. When it is brought near the paper cylinder, negative charges in the rod are attracted by the positive charges in the cylinder.

3) When the cylinder is touched by the rod, some negative charges are transferred to the rod. Hence, the negative charges in the rod are attracted by the positive charges in the cylinder. Thus, we can say that charges can be transferred to on object by bringing it in contact with a charged body. This method of transferring charges from one body to other body is called transfer by conduction

16. The materials which allow electric charges to pass through them easily are called ____

17. The process of charging an uncharged body by bringing a charged body near to it but without touching it is called ____

18. Which among the following statement is incorrect regarding the transfer of charges by
induction?

1) Bring a negatively charged plastic rod near a neutral rod. When the negatively charged plastic rod is brought close to the neutral rod, the free electrons move away due to repulsion and start piling up at the farther end. The near end becomes positively charged due to deficit of electrons.

2) When the neutral rod is grounded, the negative charges flow to the ground. The positive charges at the near end remain held due to attractive forces and the electrons inside the metal is zero. When the rod is removed from the ground, the positive charge continues to be held at the near end. This makes the neutral rod a positively charged rod.

3) Similarly, when a positively charged rod is brought near an uncharged rod, positively charged protons are attracted towards it. As a result, there is excess of proton at nearer end and deficiency of protons at the farther end. The nearer end of the uncharged rod becomes negatively charged and far end is positively charged.

19. Flow of positive charge is called _____

20. Which among the following statement is correct

1) Suppose you have two metallic spheres; one having more negative charge (excess of electrons) and the other having more positive charge (deficiency of electrons). When you connect them both with the help of a metallic wire, excess electrons from the negatively charged sphere will start flowing towards the positively charged sphere.

2) This flow continues till the number of electrons in both the sphere is equal. Here, the positively charged sphere is said to be at lower potential and the negatively charged sphere is said to be at higher potential. Hence, electrons flow from lower potential to higher potential. This is known electric current (flow of electrons).

21. The potential difference is commonly known as _____

22. Which is a scientific instrument used to detect the presence of electric charge on a body?

23. In the year 1600, which British physician invented the first electroscope?

24. There are how many types of electroscope?

25. Which among the following statement is correct

1) An electroscope is made out of conducting materials, generally metal. It works on the principle that like charges repel each other. In a simple electroscope two metal sheets are hung in contact with each other. They are connected to a metal rod that extends upwards, and ends in a knob at the end.

2) If you bring a charged object near the knob, electrons will either move out of it or into it. This will result in charges on the metal leaves inside the electroscope. If a negatively charged object is brought near the top knob of the electroscope, it causes free electrons in the electroscope to move down into the leaves, leaving the top positive. Since both the leaves have negative charge, they repel each other and move apart.

3) If a positive object is brought near the top knob of the electroscope, the free electrons in the electroscope start to move up towards the knob. This means that the bottom has a net positive charge. The leaves will spread apart again.

26. The first electroscope developed in 1600 by William Gilbert was called ____

27. The gold-leaf electroscope was developed in 1787 by a British scientist named _____

28. Which are used in Gold-leaf electroscope because they are the best conductors of electric current?

29. Which among the following statement is correct regarding Gold-leaf electroscope

1) Gold-leaf electroscope is made up of a glass jar. A vertical brass rod is inserted into the jar through a cork. The top of the brass rod has a horizontal brass rod or a brass disc. Two gold leaves are suspended from the brass rod inside the jar.

2) When the brass disc of the electroscope is touched by a charged object, electric charge gets transferred to the gold leaf through the rod. This results in the gold leaves moving closer to each other. This happens because both the leaves have similar charges.

3) The gold leaves resume their normal position after some time. This happens because they lose their charge. This process is called electrical discharge. The gold leaves would also be discharged when someone touches the brass rod with bare hands. In that case, the charge is transferred to the earth through the human body.

30. Transfer of charge from one object to another is called ____

31. Which is produced by discharge of electricity from cloud to cloud or from cloud to ground?

32. Which among the following statement is correct

1) Getting a shock from a doorknob after rubbing your foot on a carpet floor, results from discharge. Discharge occurs when protons on the hand are quickly pulled to the positively charged doorknob. This movement of proton, which is felt as a shock, causes the body to lose negative charge. Electric discharge takes place in a medium, mostly gases.

2) During thunderstorm air is moving upward rapidly. This air which moves rapidly carries small ice crystals upward. At the same time, small water drops move downward. When they collide, ice crystals become positively charged and move upward and the water drops become negatively charged and move downward.

3) So, the upper part of the cloud is positively charged and the lower part of the cloud is negatively charged. When they come into contact, electrons in the water drops are attracted by the positive charges in the ice crystals. Thus, electricity is generated and lightning is seen.

33. A safety measure devised to prevent people from getting shocked if the insulation inside electrical devices fails is called _____

34. Which among the following statement is correct

1) Sometimes the lower part of the cloud which is negatively charged comes into contact with the positive charges accumulated near the mountains, trees and even people on the earth. This discharge produces lot of heat and sparks that results in what we see as lightning.

2) Huge quantities of electricity are discharged in lightning flashes and temperatures of over 30,000°C or more can be reached. This extreme heating causes the air to expand explosively fast and then they contract. This expansion and contraction create a shock wave that turns into a booming sound wave, known as thunder.

3) Lightning’s extreme heat will vaporize the water inside a tree, creating steam that may burn out the tree. Sometimes thunder may be heard before the lightning is seen. This is because the distance between the clouds and the surface is very long and the speed of sound is much faster than the speed of light.

35. Which among the following statement is correct

1) We get electrical energy from different sources. Battery is one such source. We use it in wall clocks, cell phones etc. For the working of refrigerators, air conditioners, washing machines, televisions, laptops and water heaters we use domestic power supply. Usually, an electric appliance such as a heater, an iron box, etc. are fitted with three wires namely live, neutral and earth. The earth wire is connected to the metallic body of the appliance. This is done to avoid accidental shock.

2) Suppose due to some defect, the insulation of the live wire inside an electric iron is burnt then the live wire may touch the metallic body of the iron. If the earth wire is properly connected to the metallic body, current will pass into the Earth through earth wire and it will protect us from electric shock. The Earth, being a good conductor of electricity, acts as a convenient path for the flow of electric current that leaks out from the insulation.

36. Which is a device used to protect buildings from the effects of lightning?

37. If two terminals of a battery which are at different potential are connected by a metallic wire, electrons will flow from which terminal to which?

38. The path through which electrons flow from one terminal to another terminal of the source, is called _____

39. Which among the following element consist of simple circuit?

40. Which among the following statement is correct

1) The source can be a battery or the electric outlet in your room. The electrical resistor refers to the device that consumes the energy. Control (key) is the mechanism that is used to start, stop and regulate the electric current.

2) When the key is on, electrons from the battery flow through the circuit from the negative terminal through the wire conductor, then through the bulb and finally back to the positive terminal. The light glows when current is flowing through its filament.

41. Which is a species of fish which can give electric shocks of upto six hundred fifty watts of electricity?

42. Which circuit has more than one resistor (bulb) but only one path through which the electrons can travel?

43. In a series circuit which through the circuit remains same throughout the circuit?

44. How many ways we can connect the electric circuit?

45. Which among the following statement is incorrect regarding series circuit?

1) In this series circuit, charges (electrons) from the battery have only one path to travel. Here battery, key and two bulbs are connected in series. Charges flow from the battery to each bulb, one at a time, in the order they are wired to the circuit. If one bulb in the circuit is unscrewed, the current flow to another bulb would be interrupted.

2) We put serial lights during festivals. If the lights are in a series circuit, one burned out bulb will keep all the lights off. If the number of bulbs in a circuit with a battery increases, the light will be dimmer because many resistors are acting on the same power from the battery.

46. Let us consider three bulbs connected in series. Let I be the current through the circuit and V1, V2, V3 be the voltage across each bulb. The supply voltage V = ?

47. Which among the following statement is correct

1) In a parallel circuit, there is more than one resistor (bulb) and they are arranged on many paths. This means charges (electrons) can travel from one end of the cell through many branches to the other end of the cell. Here also current across the resistors (bulbs) remains the same but the voltage flowing through the circuit gets divided across each resistor.

2) In the above diagram current can flow in two paths: ABEFA and ABCDEFA. Here, it is clear that electricity from the cell can take either path ABEFA or path ABCDEFA to return to the cell. From the diagram you will notice that even when one resistor (bulb) burns out, the other bulbs will work because the electricity is not flowing through only one path.

3) All the light bulbs in our homes are connected in parallel circuit. If one bulb burns out, the other bulbs in the rooms will still work. The bulbs in a parallel circuit do not dim out as in series circuits. This is because the voltage across one branch is the same as the voltage across all other branches.

48. Which among the following equation is correct for parallel circuit?

49. Which among the following statement is correct

1) In a series circuit different amount of current flows through all the components. Voltage is different across different components. Components are arranged in a line. If one component breaks down, other components will function.

2) In a parallel circuit the current flowing through each component combines to form the current flow. Sum of the voltage through each component will be the voltage drawn from the source. Components are arranged parallel to each other. Other components will function even if one component breaks down.

50. Electric energy can be converted into which among the following energy?

51. The process of depositing a layer of one metal over the surface of another metal by passing electric current in called _____

52. Which among the following statement is correct

1) Take two pieces of wire, an LED light and a battery, and make a simple electric circuit. Take some water in a glass and put the wires in the water as shown in the figure. We saw that electricity is conducted by metals. This activity shows that liquids also conduct electricity. When electric current is passed through a conducing solution, some chemical reactions take place in the solution.

2) These chemical reactions produce electrons which conduct electricity. This is called chemical effect of electric current. The decomposition of molecules of a solution into positive and negative ions on passing an electric current through it, is called oxidation. Oxidation has a number of applications. It is used in extraction and purification of metals. The most general use of oxidation is electroplating.

53. Which among the following coat is deposited on iron to protect it from corrosion and formation of rust?

54. Which among the following statement is correct

1) Take a glass jar and fill it with copper sulphate solution. Take a copper metal plate and connect it to the positive terminal of battery. Connect an iron spoon to the negative terminal of the battery.

2) Now, dip them in the copper sulphate solution. When electric current is passed through the copper sulphate solution, you will find that a thin layer of copper metal is deposited on the iron spoon and an equivalent amount of copper is lost by the copper plate.

55. When electric current passes through a conductor, there is a considerable ‘friction’ between the moving electrons and the molecules of the conductor. During this process, electrical energy is transformed to what?

56. Which among the following wire offers very little resistance and does not get heated up quickly?

57. Which among the following statement is correct

1) Electric cookers turn red hot when electric current is passed through the coil. The heat energy produced is absorbed by the cooking pot through conduction.

2) The heating element is placed at the bottom of the kettle which contains water. The heat is then absorbed by the liquid and distributed throughout the liquid by convection.

3) When current flows through the heating element, the heat energy developed is conducted to the heavy metal base, raising its temperature. This energy is then used to press clothes.

58. What was the melting point of fuse wire?

59. Fuse is a strip of alloy wire which is made up of what?

60. Which among the following wire is used in the filaments of the bulbs?