1. The problem statement, all variables and given/known data A positive point charge (q = +8.9 10-8 C) is surrounded by an equipotential surface A, which has a radius of rA = 1.3 m. A positive test charge (q0 = +2.7 10-11 C) moves from surface A to another equipotential surface B, which has a radius rB. The work done by the electric force as the test charge moves from surface A to surface B is WAB = -8.3 10-9 J. Find rB. 2. Relevant equations VB=VA-(WAB/q0) V=kq/r 3. The attempt at a solution kq/rB=kq/rA-(WAB/q0) I don't seem to understand the concepts behind this question and cannot come up with the correct answer. I'm really lost. Any help explaining this would be appreciated.