PURPOSE: To demonstrate operation of a Van de Graaff generator and to illustrate electrostatic concepts.

DESCRIPTION: The ground sphere is positioned a few inches away from the Van de Graaff dome and grounded to the base of the Van de Graaff. When the machine is turned on, the dome becomes charged negative and the ground sphere becomes charged positive by induction. The ground sphere is attracted to the dome, as can be easily seen. After the spark, the two spheres lose their charges, and the ground sphere relaxes to its original position, whereupon the cycle repeats.

SUGGESTIONS:

REFERENCES: (PIRA 5A50.30) See Demonstration Reference File for articles dealing with how a frictional Van de Graaff generator works. There has been some controversy regarding some of the details. Click for a copy of an article from The Physics Teacher, May 1990: Richard E. Berg, Van de Graaff Generators: Theory, Maintenance, and Belt Fabrication

EQUIPMENT: Van de Graaff generator with ground sphere.

SETUP TIME: None.