Basic Gaussian Surface Conceptual Problem

fysicsandphol

So I'm pretty sure I have the right answer I just wanna make sure I am getting the idea.

There is a large solid copper cube. At the center of the cube there is a hollow sphere of radius a. At the center of the hollow sphere there is a charge Q.
What is the total charge induced on the surface of the void?

To solve it, I set up a gaussian surface enclosing the hollow sphere. Because copper is a conductor, (ignoring other forces), the E field must be zero everywhere within the solid copper, otherwise ions would move to balance the E field (right?). Therefore the closed integral of E dot dA will always be zero. This implies the charge encapsulated must be 0. This implies that there must be a total charge of -Q on the surface of the void. Is this right?

Doc Al

Yes, that's correct.

fysicsandphol

thanks