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Re: Capacitor charge, were is it?
<Snip>
THE CHARGE IS
ONLY FOUND IN THE DIELECTRIC AND ZERO CHARGE IS RETAINED BY THE PLATES.
<Snip>
Only a dielctric can store charge! In a capacitor the charge separation
occurs at the metal/dielectric interfacial points. It is still held
totally within the dielectric, however, until some closed metallic
circuit conditon occurs and the energy enters the metal plates and goes
off to do real work.
<Snip>
Dear Mr. Hull:
You are also right and wrong at the same time!
If one were to construct a capacitor of two or more large plates with air as
the dielectric - a large half circle fin variable tuning cap for example -
and one were to asume that a charge could "only be stored in the dielectric"
one could point a fan at the cap, turn it on and displace all of the original
air molecules from both *between* and *around* the plates, thereby totally
"removing" the original dielectric. One would expect, - based on your narrow
assertion - that all of the charge held by the capacitor would necessarily
dissipate with the "dielectric". This I assure you would most certainly
*not* happen. Ergo, your hypothesis that the "charge is ONLY found in the
dielectric" is necessarily bogus!
Here's what I propose:
One: Where there is no physical dielectric - a vacuum cap for instance - the
"charge" is stored in a field which surrounds the plates. This results in a
low capacity per size.
Two: Where there is a physically solid dielectric - polypropelene for example
- the "charge" is stored to a great extent in the dielectric as a physical
distortion. This leades to potentially greater permittivity (stroage
capability) than would be possible with a "field only" (vacuum) capacitor.
One should in this case be able to carefully remove the dielectric from
between the plates and still measure a small residual charge equal to the
charge of a like sized vacuum (or air) cap. This could be tested.
Three: In the strange case of a non soild but yet physical dielectric - air
for example - I would expect that some small portion of the charge *would* be
stored in the air dielectric although most would be stored in the field
around the plates. This might result in a *slight* lessening of the charge
of the cap - if one were to displace the original air molecules with a fan -
to what it would be as a field only (vacuum) cap. This could also be tested
and would be a fascinating experiment for someone with a lab.
Fascinatig discussion.
Sticks and Stones welcome! <;)
-DavidF-