I don't have have a special name for Ludwik's double-positive
concentric-sphere capacitor. But I want to say this is the first I have
thought of this specific thing, and I thank Tina for bringing it up and I
thank Ludwik for his analysis and thoughts about it.
However, after thinking about it some more, I realize the same thing can
happen with regular capacitors. Although our convention in physics class is
that capacitor plates are charged equal-opposite, there is no reason they
can't be charged unequal-same. In fact, this is actually common in
electronics. We have many circuits in which the capacitor is storing energy
(has an electric field in its gap) yet both plates have positive voltage
with respect to earth ground, which would typically be taken to mean both
plates have net positive charge.
This is especially interesting in light of our other discussion about charge
density on the plates of capacitors. Wouldn't the "double-positive
unequal-charge parallel-plate capacitor" need to have negative surface
density on the inside surface of the less-positive plate? And wouldn't both
plates have some positive surface density on the outside surfaces? Am I
thinking about this correctly?
Michael D. Edmiston, Ph.D. Phone/voice-mail: 419-358-3270
Professor of Chemistry & Physics FAX: 419-358-3323
Chairman, Science Department E-Mail edmiston@bluffton.edu
Bluffton College
280 West College Avenue
Bluffton, OH 45817