Capacitance electroscope

A "capacitance electroscope", or "condenser electroscope" is a type of electroscope in which a capacitor is formed in the top plate connected to the sensing leaves, by adding another plate above it, with an insulating handle, insulated from the electroscope plate by an insulating layer, usually thick varnish. The electroscope is charged by connecting one of the plates of the capacitor to the charged object to be observed while the other plated is grounded, by touching it with a finger. The contacts are then undone and the top plate is moved away. The operation reduces the capacitance between the plates, but leaves all the charge that was stored in the lower plate at the electroscope, producing a great increase on its electric potential. Low voltages can then be amplified and observed in the electroscope. These electroscopes were commonly used to study and measure the Volta effect.