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Unformatted text preview: q as it is from +q
43 d $
r q X=0 (
-2q X=d 3
x Setting U = 0 1 r 2 d r 2r d r r d 3 46 Makes Sense! Q is twice as far from -2q as it is from +q For a pair of charges:
Just evaluate U q1q2 k r r
q1 q2 (We usually choose U = 0 to be where the charges are far apart) For a collection of charges:
Sum up U q1q2 k r for all pairs...
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