Capacitor doorbell driven by Van de Graaff generator.

Capacitor doorbell driven by Van de Graaff generator. Negative charge from the Van de Graaff generator builds up on one plate. The metal ball, initially uncharged, becomes polarized. It becomes increasingly attracted to one of the plates (whichever is nearer typically). Eventually it hits the plate, gains a charge and becomes repelled and attracted to the opposite plate. The cycle then repeats. The clanging of ball against plate is quite audible. NOTE: Shut off Van de Graaff when ringing begins. CAPACITANCE.