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Re: how many volts ?



Martha wrote:
* * *
I think there are two separate discussions going on here. When you use
values for C (or for coefficients of capacitance), you don't have to
think about how the charges arrange themselves on the individual
conductors--isn't that the whole point of using C or Cij?
But in order to calculate C in the first place, you do need to know
details of how the charges distribute themselves, using the fact that
E=0 inside each conductor, V is constant over each, etc.
--
Martha Takats
* * *

Hi Martha,
Yes, the usual attack is to specify the voltage on each conductor
and solve LaPlace's equation. The problem then is, in principle,
done since you can now evaluate E(r) = -grad V(r) everywhere, from
which you can get sigma = epsilon*E on the conducting surfaces.
Integrating this over each conductor surface gets the Q's.
Manipulation then yields the Cij's. (Note that since the Cij's
depend only on the geometry, one can choose any convenient set
of V's for the calculation - in fact the problem can be done in
pieces eg. setting some of the V's equal to zero in each piece.)

Bob Sciamanda sciamanda@edinboro.edu
Dept of Physics
Edinboro Univ of PA http://www.edinboro.edu/~sciamanda/home.html