I'm confused on what this even looks like let alone trying to solve it. A ball of charge -50e lies at the center of a hollow spherical metal shell that has a net charge of -100e. What is the charge on (a) the hsell's inner surface and (b) its outer surface? The answers are: (a) +50e; (b) -150e. I don't get it, i thought the electric feild inside a conductor is always 0. I know this is a shell and not a soild conductor but i thought it applys to this case also.