Topic outline

    • Some Natural Phenomena

      Q33. Which of the following cannot be charged easily by friction?
      (a) A plastic scale
      (b) A copper rod
      (c) An inflated balloon
      (d) A woollen cloth.

      Ans. (b) A copper rod


      Q34. What damage is caused by lightning?

      Ans. When lightning strikes a tree, it can burn up the tree. And when a person is hit by lightning during a thunderstorm, then electric energy passes through the body of the person due to which the person get severe burns and get killed. Thus, it can cause a lot of destruction by damaging property, trees and killing people.

      Q35. When a glass rod is rubbed with a piece of silk cloth the rod
      (a) and the cloth both acquire positive charge.
      (b) becomes positively charged while the cloth has a negative charge.
      (c) and the cloth both acquire negative charge.
      (d) becomes negatively charged while the cloth has a positive charge.

      Ans. (b) becomes positively charged while the cloth has a negative charge.


      Q36. What will happen when the metal top of an electroscope is touched with a glass rod which has been rubbed with silk cloth? Give reason for your answer.

      Ans. The aluminium foil strips receive the same charge from the charged glass rod through the paper clip. The strips carrying similar charges repel each other and they become wide open.


      Q37. What happens when you touch the paper clip of a self-made Electroscope? Why does it happen? What is this process called?

      Ans. Every time the foil strips collapse as soon as we touch the paperclip with hand. The reason is that the foil strips lose charge to the earth through our body. The process of transferring of charge from a charged object to the earth is called earthing.


      Q38. How can we determine if an object is charged or not?

      Ans. An electroscope may be used to detect whether a body is charged or not. When the object is touched with the metal cap of an electroscope, both the metal cap and the leaves acquire the same charge from the charged object through the paper clip. It will cause the leaves to diverge showing that the object was charged.

      Q39. What is lightning conductor? How does it work?
      How does a lightning conductor protect a tall building?

      Ans. Lightning Conductor is a device used to protect buildings from the effect of lightning. A metallic rod, taller than the building, is installed in the walls of the building during its construction. One end of the rod is kept out in the air and the other is buried deep in the ground. The rod provides easy route for the transfer of electric charge to the ground.


      Q40. What are the various effects of an earthquake?

      Ans. The various effects of an earthquake are:

                              i.        They can cause immense damage to buildings, bridges, dams and people. There can be a great loss to life and property.

                            ii.        The earthquakes can cause floods, landslides and tsunamis.

                           iii.        A major tsunami occurred in the Indian Ocean on 26th December 2004. All the coastal areas around the ocean suffered huge losses.


      Q41. What will you do to protect yourself from lightning if you are in an open field?

      Ans. If no shelter is available and we are in an open field, we should stay far away from all trees. We should stay away from poles or other metal objects. We should not lie on the ground instead we should squat low on the ground. We should place our hands on our knees with our head between the hands. This position will make us the smallest target to be struck.

      Q42. Explain why a charged balloon is repelled by another charged balloon whereas an uncharged balloon is attracted by another charged balloon?

      Ans. A charged balloon is repelled by another charged balloon because both the balloons have same type of charges and like charges repel each other. Whereas an uncharged balloon is attracted by another charged balloon because charged balloon induces opposite charges in the nearer end of the uncharged balloon by electric induction and unlike charges attract each other.


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