Gauss's Law and Charges on Conductors

[emilyz228]

A hollow conducting sphere has no net charge. There is a positive point charge at the center of the spherical cavity within the sphere. You connect a conducting wire from the outside of the sphere to ground. Will you measure an electric field outside the sphere?

I know that since the electric field inside of the conductor must be zero, that means the charge within the conductor must be zero. This means that there is a evenly distributed negative charge on the inner surface of the conductor, yielding a net charge of zero. The outer surface of the sphere then must have a positive charge in order for the sphere to have no net charge.

My question is then once the ground wire is connected to the outside of the sphere, electrons will flow from ground to the sphere to neutralize the positive charge on the outside. But what happens to the inside of the sphere? Nothing? Does this mean that once the conducting wire is connected from ground to the outside of the sphere that the sphere will then have a net negative charge?

 

[jbsteele]

But I thought that the electric field outside the sphere has to be zero due to the no net charge?No, you will not measure an electric field outside the sphere. When the ground wire is connected to the outside of the sphere, electrons will flow from ground to the sphere to neutralize the positive charge on the outside. This creates a net negative charge on the inside of the sphere, which cancels out the positive charge at the center of the cavity. This means that the sphere will have no net charge, and thus there will be no electric field outside the sphere.