Function of the collecting electrode in a Van de Graaf generator

Abstract

In the Van de Graaff electrostatic generator the electric charge at a high voltage is stored on a metallic collecting electrode. In 1933 Van de Graaff et al. stated that the spherical collecting electrode is similar to a Faraday's icepail. A new explanation of the generation of the high voltage in the above generator was presented in 1954 by Simon. It is based on a different fundamental principle, namely, the Volta's condensing electroscope principle. Simon concluded that if the spraying system is maintained at a constant potential, the collecting electrode will also attain a constant potential, the magnitude of which will be proportional to that of the spraying system. The factor of proportionality does not depend on the capacity of the collecting electrode but depends on the height of the machine. The results of the experiments performed on a self-exciting generator of Becker type indicate that the voltage of the generator does not depend on the metallic sphere and the voltage is increased as the height is increased even though the same collecting system is used. This is qualitatively in accordance with the Simon's theory.