An electroscope consists of a metal rod – electrodes and two sheets of foil or paper suspended from it. The principle of operation of the electroscope is based on the fact that forces of mutual repulsion act on bodies of the same name. When a charged object touches the electrode, the charges flow through the electrode onto the foil sheets, the leaves turn out to be similarly charged and therefore deviate from each other. So that the foil leaves do not vibrate from the movement of air, they are usually placed in a glass vessel. Air can then be evacuated from the vessel to prevent rapid charge leakage from the foil. If a body charged oppositely is brought to a charged electroscope, then the angle between its leaves will begin to decrease. Consequently, the electroscope makes it possible to determine the sign of the charge of an electrified body.
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