Van de Graaff generator

Van de Graaff generator is a simple mechanical device that enables to make static charges and potentials with up to millions of volts. The charge is transported by a rubber or silk belt from the base to the hollow sphere at the top. It is ingenious that the charge is transported to the inside of the sphere. Even if the sphere has a huge potential, there are no charges inside it, just as inside of any conductor. The charge from the belt is therefore readily transferred to the sphere, and the voltage is thus limited just by the spark discharges from the sphere and leakage currents along the column. One can make a number of beautiful experiments with the generator. For example, the third picture shows a piece of paper that will soon get charged from the sphere and will fly away. The separated hairs of a girl in the second row are a sign of the high voltage. The last row shows a charged ball that is expelled from the sphere and visualization of electric field lines by soap bubbles.