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Re: Flat conductors (was I need help).



On Tue, 26 Feb 2002, Ludwik Kowalski wrote:

To see the equipotential lines A, B, C and D plotted, and
compared with simple theoretical lines, click below.

http://blake.montclair.edu/~kowalskil/elec/eqp2.html

Your experimental data generally reflect the type of distortion
that would necessarily be caused by the existence of the
boundaries, but they also appear to be in pretty significant
disagreement with the theoretical requirement that the
equipotentials be perpendicular to the edges of the paper. Did
you measure carefully right out to the edge to see if the lines
become perpendicular?

The image charge calculations I did assumed a potential difference
of 10 units between the midplane and what is essentially a circle
of diameter 1 unit centered 5 units above the midplane. I chose
dimensions of 20 x 14 for the half sheet to match your drawings.
Translating my results to a 300 V potential difference between the
poles (and assuming that you used circles of 1 cm diameter for
your poles), my results would suggest that the potential at the
intersection of the dipole axis and the paper edge should be about
222 V, that the potential of either corner should be about 213 V,
and that the potential half way between a corner and the 150 V
midplane should be about 200 V.

On the basis of these results, I'm going to guess that your
circles are actually smaller than 1 cm in diameter, but that
wouldn't be quite enough to explain what appears to be some pretty
significant equipotential shape discrepancies especially in the
case of your 187 V line.

John Mallinckrodt mailto:ajm@csupomona.edu
Cal Poly Pomona http://www.csupomona.edu/~ajm