What is the electric potential at the center of the square shown in the figure below? Assume that q1 = 1 x 10-8 C, q2 = -2 x 10-8 C, q3 = 3 x 10-8 C, q4 = 2 x 10-8 C and d = 1 meter.

Answer 1

Potential is a scalar, so you can add the potential at the center from each of the corners.

Vcenter=Vc1+Vc2+...=kq1/d+kq2/d + ...