Gauss's law?

Question

a solid conductor has a cavity in its interior. would the presence of a point charge inside the cavity affect the electric field outside the conductor? why or why not?would the presence of a point charge outside the conductor affect the electric field inside the cavity? again, why or why not?

Answer 1

Gauss Law states that the flux across a surface is proportional to the charge enclosed. For a point charge inside of a conductor, there will be a charge enclosed and so there will be an electric field. If the charge is outside the conductor, there will be no charge enclosed and the electric field will be zero inside.

Note that this is in conflict with the previous answer by nyphdinmd above. This shielding effect of a conductor is referred to by the name "Faraday cage."

Answer 2

The conductor "shorts out" the electric field. The conductor acts as a surface of constant potential so there is an induced charge on the surface of the sphere due to the presence of the point charge in the cavity hence there is a field outside the conductor Same argument in reverse for a field outside the conductor - it creates a field in the cavity/