1. The problem statement, all variables and given/known data A metal sphere of radius R carries a total charge Q. What is the force of repulsion between the "northern" hemisphere and the "southern" hemisphere? 2. Relevant equations 3. The attempt at a solution Since the sphere is metallic, its conducting and so the electric field inside the sphere is 0, and outside the sphere it is perpendicular to the surface and is radially outwards, and so, the force exerted by the northern hemisphere on the southern hemisphere should be 0. However, the answer appears to be other than zero. why?