Basic Gaussian Surface Conceptual Problem

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In the scenario of a solid copper cube with a hollow sphere containing charge Q at its center, the total charge induced on the surface of the hollow sphere is -Q. This conclusion is based on the principle that the electric field inside a conductor must be zero, leading to the requirement that the enclosed charge must also be zero. Consequently, the induced charge on the inner surface of the hollow sphere balances the charge Q, resulting in -Q on that surface. The reasoning is confirmed by the application of Gauss's law, which supports the assertion that the electric field inside the conductor remains null. Thus, the understanding of charge distribution in conductors is validated.
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So I'm pretty sure I have the right answer I just want to 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?
 
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Yes, that's correct.
 
thanks
 
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