Re: Scotch tape, "Sticky Electrostatics"

[Leigh Palmer <palmer@sfu.ca>]

> Although this seems to make it clear that placing the top plate of the
> Electrophorus in contact with the dielectric/plate sandwich and discharging
> the top plate simply by touch is the means of continually providing a given
> charge to that plate, I recall that the method of initially charging the
> dielectric, traditionally pitch or resin, but which may be substituted with
> glass, is given as frictional rubbing.

The generation of charge with an electrophorous has nothing to do
with contact; the electrophorous works by induction. The surface
is typically charged initially triboelectrically (by rubbing it
with a suitable fabric or fur) and thereafter need not be touched.
The fact that in practice the surface is touched is incidental;
no charge need be transferred. Any charge that is transferred
leads to a decreased performance and requires replacement by more
rubbing.

> Come to think of it, what was perhaps the prototype of all electric
> generators - a ball of sulphur turned with a handle was charged by
> stroking the rotating surface with the hands.
> This was undoubtedly described as frictional charging.

Yes. That is the generator I was thinking of when I suggested to
Bill that a rotating jug would be an appropriate source for his
marvelous electrostatic bottle motor.

Leigh