Static Electricity: Point Discharge

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Charge Distribution on a Conductor

All static charges reside on the outside of a conductor (because the charges will be of the same type, and will try to get as far as possible from each other)

Static charge tends to accumulate where the conductor is most pointed

Point Discharge

At a very sharp point there is a large accumulation of charge

This creates a very strong electric force field in the region around this point

Ions in the air are either strongly attracted or strongly repelled from the tip of a charged conductor

Can be demonstrated using a Van de Graaff generator

Lightning conductors are based on this phenomenon

Van de Graaff generator

Instrument used to demonstrate electrostatic effects

Smooth dome is insulated from earth by tall support pillars

Rubber belt moves on a motor-driven pulley

Two metal combs - one at the lower pulley connected to earth and one at the upper pulley connected to the dome

The voltage (amount of static charge) of the generator depends on the size of the dome and the quality of the insulating pillars

All of the charge resides on the outside of the dome

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