Inside a hollow charged conductor in electrostatic equilibrium, the electric field is

Explanation

Charges on a conductor arrange themselves on the outer surface until the field inside cancels completely; any residual field would move the free electrons until it did. This is the basis of the Faraday cage, which is why a car is a relatively safe place in a lightning storm and why sensitive equipment is shielded in metal boxes. The field just outside the surface, by contrast, is not zero.