Question

What is an electroscope? Explain the structure of gold leaf electroscope.

Answer 1

Electroscope

1. An electroscope is a device used for the detection of a small amount of charge on a body.
2. It also gives information about the nature of the charge. i.e., negative or positive.
3. The most widely used electroscope are
   1. Pith Ball electroscope
   2. gold-leaf electroscope

Structure of gold-leaf electroscope:

1. Gold-leaf electroscope was developed by British physicist Abraham Bennet in 1787.
2. It consists of a glass bell jar fitted with an insulated plug made of cork at its mouth.
3. A thin metallic rod usually of brass passes through the cork into the glass jar.
4. The upper end of the brass rod which lies outside the jar carries a small brass cap or a disc, where the charge to be tested is applied.
5. The lower end of the rod which is inside the jar carries two thin metallic leaves hanging parallel to each other.
6. In earlier electroscopes, these leaves were made of gold that is how the electroscope got its name, gold leaf electroscope.
7. These leaves are very sensitive even to the small distribution of charge, for example, the charge induced on a comb that has been passed through dry hair can be easily detected by them.
8. The leaves in the jar are often surrounded by grounded metal plates or foil strips attached to the inner surface of the jar.
9. These are used to protect the leaves from any damage.
10. When the electroscope is in use, these plates are connected to the ground.
11. In case of an excessive flow of charge through the leaves diverge and touch the metal plates and the excess of charge flows to the ground.
12. The leaves are enclosed in a glass jar so as to protect them against air drag.
13. The whole arrangement rests on an insulated base usually made of wood