Re: How many volts ?

["Richard W. Tarara" <rtarara@saintmarys.edu>]

This sounds better than my quick try.  In terms of really 'reasoning' this
behavior, you have to consider the 'tug of war' between the negative
charges (Q1) pulling the positive charges (Q2) to the inside surface and
the excess positive charges of Q2 trying to repel each other--and thus
causing the charges to spread out and get as far away from each other as
possible--I forgot to think about this on my earlier reply.   After John's
reply I asked myself, why all 100nC of the positive charge doesn't get
pulled to the inside of the plate since there is SOME negative charge on
the second?   I like the question, even it it made me look dumb. ;-)

Rick

> From: John Mallinckrodt <ajmallinckro@CSUPomona.Edu>
> To: phys-l@atlantis.cc.uwf.edu
>
> Assuming that you can make the standard infinite sheets approximation,
> there would be +45 nC on the outer surfaces of both sheets, +55 nC on the
> inner surface of one and -55 nC on the inner surface of the other.  The
> field inside would not depend on the charges on the outer surfaces, so
the
> result is that of a capacitor charged with 55 nC and the potential
> difference would be 62 V.
>
> This is a result of applying Gauss' law and using the condition that E =
0
> inside the plates.  In essence you have a 110 nC *difference* which leads
> to the "55 nC total charge" result and a 90 nC *excess* which must be
> shared equally between the outer plates of both capacitors.
>
> John
> ----------------------------------------------------------------
>   A. John Mallinckrodt      email:  mallinckrodt@csupomona.edu
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