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Re: Ions

On Tue, 13 Apr 1999, Ludwik Kowalski wrote:

The question I have is how to distinguish a "pseudo neutral" sphere
of electrified plastic (negative cloud inside and a layer of equal positive
charge outside) from the really neutral one (where each dV is neutral)?
Perhaps "macroscopically neutral" and "microscopically neutral" terms
would be more appropriate.

But if your dV is small, you'll start seeing individual nuclei, and it
won't be neutral anymore. A really small dV would see virtual charges
even in a hard vacuum.

This is a problem throughout physics (and electronics), where the meaning
of "charg" varies nonsensically.
An uncharged
metal ring can support an immense flow of charge.
A charged capacitor is
neutral, even though the plates are charged. Everyday matter contains
huge amounts of "uncharged" charge.

In the early grades, an unsatisfactory solution is used: the stuff that
flows inside a wire is called "current" rather than charge, while the
stuff that appears on the surface of a high-voltage conductor is called
"static electricity" even if it is flowing. (So, your glass ball would be
filled with "current", although the "current" would be non-moving. Static
current?! ) Fairly advanced textbooks speak of "current flow" rather than
"charge flow", and they call electrons by the name "current carriers"
rather than "charge carriers."

Maxwell called it "free electricity" and "combined electricity", but
"free" incorrectly implies mobility and therefor conductivity.

I've been pushing "separated charge" or "charge imbalance" as a
replacement for the term "static charge", and I often state that electric
currents in a wire are a flow of "combined charge." However, I'm very
aware that this is not an ideal solution. A dipole has "separated charge"
and a strong e-field when viewed from nearby, but it turns into "combined
charge" with zero e-field if we view it from afar. Yet the dipole itself
didn't change.


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