I'm really lost on this topic, and my book stinks at conceptual explanations; my confusion is with the net charge of zero inside a conductor. Why is this so? Those lame explanations don't ring any bell; sounds more like biology to me ("this is so because we see it as so and because it is good as so"). Also, the book keeps reasserting its statements assuming that I already agree with it that E=0. That's like trying to prove a constant using the constant in the proof. Gee.
I get the mutual repulsion thing; if there's charge, it will spread out. But why not leave some charge inside too? After all, if you're gonna have all that charge on the outside, eventually it will make more sense for the charge to occupy a less pressurized space.
Also, imagine we have an electrostatic equilibrium. Now what if I put a strong charge opposite to that of what lies on the outside of that copper conductor. Now the net electric field will be all messed up, won't it? And what if I put the same charge? How are any of those going to 'calibrate' and form a net zero field?
And for the cavity one, this rings even less bells. Why not gather on the inside of the cavity?
Furthermore, on that last one, won't the charges just fly apart?? What will make them all just magically stand in place? Or is it assuming that 'plastic coating' shell?
Any clues? I'm tired thinking about this, I need to move on. Any help would be greatly appreciated. Thanks!