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Re: Electric fields and points of stability



----- Original Message -----
From: "John Mallinckrodt" <ajm@CSUPOMONA.EDU>
To: <PHYS-L@lists.nau.edu>
Sent: Monday, October 14, 2002 1:12 PM
Subject: Re: Electric fields and points of stability


... what if you place charges on the vertices of a cube. Now does
an equilibrium point exist? It seems that it should - at the center
of the cube - but what happens to the field lines at that point?
(There is no additional dimension to remove them).

An equilibrium point exists at the center of the cube ONLY if all the
charges at the vertices have the same magnitude and the same sign.

Field lines from (or to) each charge lie symmetrically around each body
diagonal. As they approach the center, they veer away symmetrically on
either side so that the center is devoid of lines.

Does this violate the (textbook) rule that field lines start and end on
charges? If it does, are there any other comparable violations?

No. All the lines end on charges an infinite distance away whose sign is
opposite to the sign of the vertex charges.

This posting is the position of the writer, not that of SUNY-BSC, NAU or the AAPT.