Re: Influence machine

[Leigh Palmer <palmer@sfu.ca>]

> Sorry, but as far as I know, electrostatic induction is not
> the basic process for generating charges on the Wimshurst machine.
> The starting point seems to me to be the charging of any plate
> of one of the discs by means of friction: recall there are
> cupper filaments rubbering these metallic plates.
> (this may not be the only way for a plate to get charged)

The Wimshurst machine is a self-excited electrostatic generator
in the operation of which friction (triboelectricity) plays no
fundamental role. Like the Kelvin water dropper it is a
symmetric device. In principle it can be run with either
polarity, the "choice" being a random one determined by the
statistical fluctuation of charge on macroscopic objects. The
electrophorus (and some Van de Graaffs) is an induction machine
in which the polarity may be determined by triboelectricity, but
the sustained operation of which depends solely on induction.

For triboelectricity to be an important ongoing mechanism in the
operation of an electrostatic generator there must be some
intrinsic asymmetry present.

Leigh