Re: contact electrification

[David Bowman <David_Bowman@GEORGETOWNCOLLEGE.EDU>]

Regarding John Denker's comment #2):

> 2) It has been known for about 200 years that, strictly speaking, there is
> no such thing as a triboelectric series.  Depending on the chemical and
> physical state of the surfaces, I can create objects A, B, and C that obey
> the nontransitive relationships
>        x(A,B) > 0
>        x(B,C) > 0
>        x(C,A) > 0
> where x(,) designates the charge of the first object when
> contact-electrified against the second.  It is even possible to have two
> objects D and E such that
>        x(D,E) > 0 if you rub gently, while
>        x(D,E) < 0 if you rub harder.
>
> A related but easier-to-visualize piece of physics is this:  given fixed
> terminals (A1 and A2) made of absolutely identical material (A) plus a
> moving part of type B, I can create a generator which uses contact
> electrification to move charge from A1 to A2 at a steady rate.  Does that
> imply A > B > A????

Along these lines it is even possible to have x(A,A) > 0 where the
substance A of the first argument is chemically the same with the same
crystal structure as the A of the second one with the only difference
between them being their temperature.  Not only this, but which direction
the charge is transferred relative to which way the temperature imbalance
goes *itself* can be temperature dependent.

A nearly ubiquitous example (and maybe "dramatic" enough to suit Leigh,
but going strictly by memory/memorism) is that of the electrification
that takes place in thunderstorm cells.  Ice contacting ice at a
different temperature will transfer charge.  Which way the charge is
transferred relative to the temperature difference is itself (as I think
I recall) a temperature dependent property.

David Bowman
David_Bowman@georgetowncollege.edu