ELECTROSCOPE
Electroscope is a
device used for detecting and testing the nature of charge on a body. It
works on the principle that similar charges repel each other. A simple form of
electroscope consists of a metal bar which has a metallic sphere (ball) at its
upper end. Thin flexible metal leaf (made of gold, silver, copper or any other
metal) is attached to the lower end of metal bar. The lower part is enclosed in
an insulated housing.
Working: In
order to detect charge on a body we touch the metal ball with it. For example,
if we touch it with negatively charged rubber rod some of its excess electrons
will be transferred to the ball and then they will spread throughout the metal
rod and the metal foil.
The flexible metal leaf will be repelled by the similar charge
on the metal rod and will move away from the rod by rising higher. As more electrons
are transferred to the electroscope, the metal leaf will rise higher. Alternatively
if the rod is positively charged it will attract electrons from the electroscope,
leaving a net positive charge on it. Once again the foil will rise.
However, to test the
nature of charge on the body we charge the electroscope with some known charge
first. Now if the same charge is added to the metal ball, it will increase
divergence of flexible metal leaf and opposite charge will decrease the
divergence allowing us to identify the unknown charge on the body.
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| Electroscope |
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