NCERT Book Class 8 Science Chapter 12 Some Natural Phenomena

SOME NATURAL PHENOMENA

In this chapter we shall discuss two kind of resin) was rubbed with fur, it
destructive natural phenomena. These attracted light objects such as hair. You
are lightning and earthquakes. We shall might have seen that when you take
also discuss what steps we can take to off woollen or polyester clothes, your
hair stands on end. If you take off these
minimise destruction caused by
clothes in the dark, you even see a
these phenomena.
spark and hear a crackling sound. In
1752 Benjamin Franklin, an American
12.1 Lightning
scientist, showed that lightning and the
You might have seen sparks on a spark from your clothes are essentially
electric pole when wires become loose. the same phenomena. However, it took
This phenomenon is quite common 2000 years for this realisation to occur.
when wind is blowing and shaking the
wires. You might also have seen sparks
when a plug is loose in its socket. I wonder why they took so
Lightning is also an electric spark, but many years to realise the
on a huge scale. similarity.
In ancient times, people did not
understand the cause of these sparks.
They were, therefore, afraid of lightning
and thought that the wrath of gods was Scientific discoveries are a
visiting them. Now, of course, we result of hardwork by many
understand that lightning is caused by people. It can sometimes take
the accumulation of charges in the a long time.
clouds. We need not be afraid of
lightning, but we have to take We shall now study some properties
precautions to protect ourselves from of electric charges. We shall also see how
the deadly sparks. they are related to the lightning in the
sky.
The Sparks that the Greeks Knew Let us perform some activities to
About understand the nature of electric
The ancient Greeks knew as early as charges. But recall first what you might
600 B.C. that when amber (amber is a have played as a game. When you rub