text: electrostatics? what is the reason that a charge added to a conductor always comes up to the surface? a conductor has constant electric potential(under electrostatic conditions). this means that the electric field inside the conductor is  always zero.( e=-gradv) now, draw a gaussian surface which lies entirely in the conductor. by gauss's law, the net charge inside this surface must be zero (since e is zero and hence flux crossing the surface is zero). this is true for any other gaussian surface *entirely inside* the conductor. hence charge must be on the surface of the conductor. this is one of the ways to *understand* the phenomena but i guess it does not give the *reason*!