1. The problem statement, all variables and given/known data A metallic sphere at ##\phi = 0 ## is surrounded by a spherical layer with charge density ##\rho ##. Find the potential at every point. https://photos-6.dropbox.com/t/2/AACuekw5jWy2n0tNfMqPRKoakoEdSj24JOvheq4J6XNWRQ/12/28182931/png/1024x768/3/1421928000/0/2/spheres.png/CJOTuA0gAyACIAEoAigB/g4S2DgYrMDWxMbOXqlP8kHX8klBkIjXPbCRua9GoiiQ [Broken] 2. Relevant equations 3. The attempt at a solution The central zone is just 0. The potential in the yellow zone could be calculated assuming there is no charge in the grey zone, since that distribution would give the same boundary condition in the interior surface of the yellow zone, that is, ##\phi = 0 ##. However I don't know the potential in the outer surface, so I'm not sure if I can do that. Is there anyway to find the potential at the outer surface?