Schematic Electroscope

An electroscope is used to detect the presence of electric charges, to determine whether these charges are positive or negative, and to measure and indicate their intensity. This schematic drawing shows the basic parts of the device: (a, a_) are thin leaves of metal foil, suspended from (b), a metal support; (c) is a glass container, while (d) is a knob that collects electric charges. Electric charges (either positive or negative) are conducted to the leaves at the bottom via the metal support. Because like charges repel one another, the leaves fly apart. The amount of the charge is calculated by measuring the distance the leaves are forced apart.