Some Natural Phenomena - Exemplar Solutions 4

CBSE Class 8 Science
NCERT Exemplar Solutions

24. Explain how lightning takes place ?
Ans: A cloud consists of millions and millions of small water droplets. These droplets collide with other droplets. Due to these collisions, electrons are knocked out of water droplets, but water droplets keep rising up. Thus a charge separation occurs. The knocked out electrons form the lower layer of the cloud. The positively charged water droplets rise to a certain height and form the upper layer of cloud. Hence, there is accumulation of positive charges on the ground. When the magnitude of the accumulated charges become large, the air cannot resist their flow. As a result negative and positive charges meet producing a streak of bright light and sound, called lightning.

25. Mention three precautions that you will take to protect yourself if earthquake strikes when you are inside the house.
Ans: Three precautions that we will take to protect ourself if earthquake strikes when we are inside the house are as follows :
(i) Take shelter under a table and stay there till the shaking stops.
(ii) Stay away from tall and heavy objects that may fall on you.
(iii) If you are in bed, do not get up. Protect your head with a pillow.

26. Explain why it is safer to use a wireless telephone instead of a landline telephone during lightning.
Ans: Lightning is an electrical discharge. During lightning atmospheric electric charge may discharge through landline telephone wires and may become dangerous. Therefore, it is safer to use a wireless telephone instead of a landline telephone during lightning.

27. What precautions would you take if lightning occurs while you are outside the house ?
Ans: Precautions we will take if lightning occurs while we are outside the house are as follows 
(i) Stay away from poles or other metallic objects.
(ii) Stay away from tall trees.
(iii) Stay away from open vehicles like motorbikes, tractors, construction machinery, etc.

28. If the metal clip used in the electroscope is replaced by an ebonite rod and a charged body is brought in contact with it, will there be any effect on the aluminium strips ? Explain.
Ans: The aluminium strips will not show any repulsion. The charged body will not transfer any charge to the ebonite rod as ebonite rod is an insulator. As a result there will be no charge on the aluminium strips and no repulsion will occur.