1. The problem statement, all variables and given/known data Two charges are placed at the corners of a square. One charge, +4.0uC, is fixed to one corner and another, -6.0uC is fixed to the opposite corner. WHat charge would need to be placed at hte intersection of the diagonals of the square in order ot make the potential difference zero at each of the two unoccupied corners? 2. Relevant equations V = kq/r 3. The attempt at a solution Given that potential difference (or voltage) is calculated based on the formula above, can I just assume that the radius of this square is infinitely large and therefore V becomes zero and that the charge is some number that is much smaller than infinite? I'm not sure if I'm allowed to do this. Please help.