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Re: IONS/dielectrics



Bob Sciamanda wrote:

A while back there was a Phys-L thread concerning residual charges that
spontaneously appear on capacitors after discharge. At that time I
posted a web reference that offered an analysis. I wasn't terribly
interested (and/or too busy) and didn't really persue the subject; and I
haven't kept the reference. Perhaps you recall the discussion and can
resurrect the reference. .....

I do recall this thread very well. And I may have your message,
somewhere. You are correct; see "ELECTRETS" by Jefimenko and
Walker, The Physics Teacher, December 1980, p 651-659. A very
good reference outlining the history of the space charge ideas. They
do refer to capacitors which recharge from inside. I just found the
article last night.

I have neither time no knowledge to undertake a serious solid
state physics research project. But simple experiments, like the
one described on Tuesday are worth performing to illustrate
limited validity of textbook models. A dielectric plate removed
from a capacitor, or any piece of it, is expected to be macroscopically
neutral but reality contradicts this. The model of “aligned dipoles”
is not even approximately correct in predicting what happens in
that respect. Experiments which expose limitations of textbook
models are hard to find and worth promoting.

Ludwik Kowalski