1. The problem statement, all variables and given/known data A rectangle has sides of length 5cm (right and left) and 15cm (top and bottom). Top left corner has charge (q1) = -5uC Top right corner has charge A = ? Bottom left corner has charge B = ? Bottom right corner has charge (q2) = 2uC a) What are the electric potentials of A and B b)How much external work is required to move a third charge (q3 = 3uC) from B to A along the diagonal of the rectangle 2. Relevant equations Not too sure. For part b I'm thinking I would use a line intergral and say that the diagonal path from A to B is equivilent to going from B to q1, then q1 to A. V = U/Qo But where will I get U (potential energy) from? 3. The attempt at a solution What I really want is part a, once part a is done I can just do some line intergrals to find the work done for part b. Do I use equipotentials? So potential of A is the same as potential of q1? B is the same as q2? Any pointers and I'm very grateful.