Conducting Shell and a Metal Sphere

Question

I am have a doubt regarding the topic Conductor in Griffith's text book of Electrodynamics.

Griffiths states that, a perfect conductor contains infinite amount of charges, and a metal resembles that nature. So while solving problems, one in Griffith's too, Does it makes sense that a metal sphere has a charge q on it. As, metal already has infinite amount of charges, what does a charge q on a metal sphere would have a meaning. i.e. What is the difference between those charges that makes electric field inside a metal/conductor to be zero and all those charges exist on the surface and this charge "q", that a metal sphere has on it?

Answer 1

An uncharged metal has an equal amount of positive and negative charges. The number of protons equals the number of electrons. When the metal is charged, the number of electrons and protons are no longer equal. In an electrostatic situation, a charged sphere after all charges have relocated, the extra charge distributes uniformly on the surface of the sphere. This provides a net electric field of zero everywhere within that charged spherical shell. At this point, there is no more electric field within the sphere to move any more charges. For any conductor, excess charge will move around until the electric field due to this extra charge is zero within. As all of these extra charges pushes against each other, they end up on the outer surface.