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Re: funny capacitor



"John S. Denker" wrote:

Again we see that thinking in terms of delta_V is not the
same as thinking in terms of V.

Most physics teachers assume that V in electrostatics does
refer to a potential difference. By definition V is equal to
the amount of work per unit charge necessary to bring a
small probe charge to a conductor from another location.

My personal preference, in the funny capacitor problem,
is to use the enclosure as a reference location and to
assign V4=0 to it. I am not trying to impose this convention
on anybody. I want to know if it is possible to solve our
problem by assuming that V1, V2 and V3 are differences
of potentials with respect to a large enclosure. I have no idea
what a potential is unless it is a word referring to a difference
of potentials. The concept of "V vector" is totally new to me.
That is probably why I am frustrated.

We think that no other combination of
Vs can produce the same set of Qs.

Actually we can, if we include V4 as part of the V vector.

Can our problem be solved in terms of differences of
potentials only? What is wrong with accepting a convention
that the enclosure is our "sea level" reference? Yes, it is not
the only possible choice. But a choice must be made in trying
to solve a problem. What is wrong with this choice?
Ludwik Kowalski