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Re: Fluff for the day

At 04:37 PM 5/3/01 -0700, John Mallinckrodt wrote:
What charge, placed at the empty corner of the square, will cause
the total electric potential energy of the configuration to be
zero?

-Q............
. .
. .
. .
. .
. .
. .
Q...........Q


Can you guess what most students said?

I guess they said -Q, which has a tempting symmetry.

It is, interestingly enough, the only possible wrong answer.
Any other value can be made correct by an appropriate choice of gauge.

It's going to hurt the kids' feelings to hear that they've chosen the only
possible wrong answer.