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Re: E field and capacitance question



Hi Ludwik,

Hmm... I seem to remember somthing in the Feynman Lectures
about holes in dielectrics but I can't recall details .. but anyway it
seems to me that if you were to create a small hole in the dielectric
that the polarization charge on the surface surrounding the hole would
make the field in the cavity larger than inside the dielectric..
right? I would think this would complicate any direct measurement of
the E-Field... on the other hand if you could use a liquid dielectric
and somehow insert charges that can be observed.....

take care,
-steve

"Ludwik" == kowalskil <kowalskil@alpha.montclair.edu> writes:

Ludwik> Yesterday Tim Wilson asked a good question about
Ludwik> capacitors. We know the answer by now; the fields should
Ludwik> be identical in two capacitors. But was this actually
Ludwik> verified? I know that in a gedanken experiment this can be
Ludwik> done by "measuring" the force per unit charge in a small
Ludwik> cavity. For example, by "drilling" a very narrow channal
Ludwik> in the dielectric and using it as a tiny accelerator of
Ludwik> ions or electrons. If E are identical in the dielectric
Ludwik> and in the vacuum then the final energy in the channel
Ludwik> accelerator, and in the corresponding vacuum accelerator,
Ludwik> should be identical.

Ludwik> a) But was this, or something similar, actually done? b)
Ludwik> Do we need real experiments to verify statements which are
Ludwik> logically obvious? Ludwik Kowalski