(a) Deduce the expression for the potential energy of a system of two charges
q1 and
q2 located
→r1 and
→r2, respectively, in an external electric field.
(b) Three point charges, + Q + 2Q and - 3Q are placed at the vertices of an equilateral triangle ABC of side l. If these charges are displaced to the mid-point
A1,B1 and
C1, respectively, find the amount of the work done in shifting the charges to the new locations.
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