The electrostatic generator is a machine for producing very large electric potential differences, of the order of millions of volts. Since the chief application of these electrostatic generators is to accelerate charged particles to very high kinetic energies, they are often referred to as accelerators. The operation of a Van de Graaff generator can be explained in terms of basic principles. These same principles apply to research accelerators as well as to the classroom demonstration static generators.
Charge is separated by the rubbing of the belt against the driver roller while the belt is moving.
Positive charge collects on the roller, and an equal amount of negative charge collects on the inner side of the belt. This negative charge is less dense because it is spread over the entire length of the belt. Thus in the region of the lower roller the net charge is positive. The charged belt moves upward into a large, hollow, conducting dome. Here a conducting wire, connected to a comb of sharp points near the top of the belt, allows the negative electrons from the charged belt to flow to the dome, making the charge on the dome negative.