Page 148 - Science Class 08

The paper cylinder is repelled when it is brought near the suspended glass rod at the other end.
It shows that the uncharged rod acquired a posi ve charge when it was near the ebonite rod
which is nega vely charged. The opposite charge, makes the rods a ract towards each other.
The other end of the rod becomes nega vely charged and repels the nega vely charged paper
cylinder. The same charges on cylinder and rod repel each other. The charging of glass rod in this
way without touching it with charged object is called charging by induc on.

ELECTROSCOPE i.e., it is discharged. It is because the leaves
Electroscope is an instrument which is used to lose charge to the earth through your body.
detect and test small electric charges developed This process is called earthing. Thus we find
on a body. A gold leaf electroscope is very that electrical charge can be transferred from

sensi ve and the presence of electric quan ty one charged body to another through a metal
and nature of charge on a body can be detected detector.
by using it. You can also charge the electroscope nega vely
Let us take a simple gold leaf electroscope by touching its disc with a nega vely charged
consis ng of two gold leaves, hanging from a ebonite rod.
brass rod which carries a disc at the upper end. Finding the Nature of Charge
The rod passes through an ebonite cork fi ed First, charge the electroscope with a posi vely

in the mouth of the glass bell-jar. or nega vely charged object. When it is
Rub a glass rod with a dry piece of silk cloth. It charged, the leaves of the electroscope will
will get posi vely charged. Touch the disc of the diverge or open up. Now, bring the object
electroscope with the posi vely charged glass which is to be tested to detect the nature of
rod. What do you no ce? You will observe that charge on it. If the charged object has the same

the leaves get diverged due to similar posi ve charge (say nega ve) as on the electroscope,
charges on them. The electroscope leaves the leaves will diverge or open up more. If the
remain diverged, even when you remove the charged object has opposite charge (say
glass rod. This shows that the electroscope is posi ve) to that of the electroscope, the leaves
charged by conduc on. will come closer or converge.

Glass Rod

How Much Charge Does an Object Have?

Charging an electroscope by conduc on. The divergence or opening and convergence or
Now, touch the disc of the electroscope with closing of the leaves of electroscope is the
your hand. You will find that its leaves collapse, measure of the charge on an object. If the

148 Science-8