The Standard Electrical Dictionary

1. Machine, Frictional Electric

   An apparatus for development of high tension electricity by contact action, brought about by friction. It consists of a plate or cylinder of glass mounted on insulating standards and provided with a handle for turning it. One or more cushions of leather are held on an insulated support, so as to rub against the plate or cylinder as it is turned. A metal comb or combs are held on another insulating support so as to be nearly in contact with the surface of the glass plate at a point as far removed as possible from the rubbers. The combs are attached to a brass ball or round-ended cylinder, which is termed the prime conductor. In use either the prime conductor or cushions are connected by a chain or otherwise with the earth. Assume it to be the cushions. As the machine is worked by turning the plate, the glass and cushion being in contact develop opposite electricities. The glass is charged with positive electricity, and as it turns carries it off and as it reaches the prime conductor by induction and conduction robs it of its negative electricity. Meanwhile the cushions negatively excited deliver their charge to the earth. The action thus goes on, the prime conductor being charged with positive electricity. If the prime conductor is connected to the earth and the cushions are left insulated, negative electricity can be collected from the cushions. In some machines both prime conductor and cushions are kept insulated and without ground contact. Electrodes connecting with each are brought with their ends close enough to maintain a sparking discharge.