The upper plate is connected to the prime conductor of an electrostatic machine, and the lower plate grounded. The demonstration starts with pith balls or paper figures lying on the lower plate. They become charged by induction, and are attracted to the upper plate. Once there, they pick up a charge and are repelled downward. The process then repeats itself.
The apparatus at the far right is in the Garland Collection of Classical Physics apparatus at Vanderbilt University.
The electric hail at the left below is at Transylvania University in Lexington, Kentucky, and the identical apparatus at the right is in the Garland Collection of Classical Physics Apparatus at Vanderbilt University.
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