While I was studying about capacitors I realized that charge on the outer surface of the plates is zero when both the plates are given equal and opposite charges. Now mathematically, this realization came to using the fact that the net field inside any point inside the plate must be zero.
But practically, looking at the electrons' behavior, does this mean that all the charges come together because they are kept so close? Would the plate have equal charges have throughout their respective surfaces when kept far apart but not at infinity?
I tried to visualize this myself, but I am not confident with my thought process. First of all, I imagined that in the above situation, the positive charges, or the "voids" grouped together on one surface only because they were kept so close, and similar happened with the electron. Following this, I now pictured two plates, one with charge Q and other with none. They are brought near and according to my thought process, it must be Q and -Q, as due the small distance, the "gaps" and the electrons all should rush towards the gaps. So the Q on the originally charged plate attracts all the -Q equivalent electrons, leaving a "void" of +Q on the other surface. But when I tried using the fact that the net electric field inside either of the plates must be zero, I was instead left with charges +Q/2 and -Q/2 and +Q/2 on the outer surface of both the plates.
So where was the flaw in my thinking? I just assumed that the +Q would attract all the electrons worth -Q. But why does this not happen. This means that my thinking in the very first question, though gave me the right answer, but apparently was not correct.
I was looking for an explanation but was unsuccessful in it. Please note that I have already derived what charges should appear on the plates and I am aware of that. I am just looking for a more 'intuitive' or 'imaginable' reason as to why the electrons behave like this.
As a brief example, consider a point charge q, which is brought near a neutral, spherical conducting sphere. So the sphere must gain -q near the point charge and +q on the other side. Why doesn't the same happen with the metal plates?
Also, does the same happen with concentric conducting shells? Like, if the inner shell is charged to some charge, would the same charge appear on both sides of the outer shell?