1. The problem statement, all variables and given/known data My questions are just related to part a of this problem. 2. Relevant equations 3. The attempt at a solution I know that potential inside a conductor is equivalent to potential on the surface of the conductor and potential at any point is an algebraic sum of potential contributions from surrounding sources. But this is as far as I got.. I gathered that potential on surface of b is 0, as net charge of the sphere is 0 (after treating both spheres as point charges of +q and -q). By my previous statement, shouldn't potential inside sphere b (for example r_a < r < r_b) 0 as well? Could anyone point out the gaps in my understanding? Any help is very much appreciated.