Suppose a lightning bolt strikes a car. The car's body is induced with electric charges on its surface. Will there be any charges on the car's inner surface? Here, the car's metallic body can be approximated as a conductor with a cavity. Since the conductor itself is in electrostatic equilibrium, there should not be any electric field inside the conductor. Hence, from Gauss' law, the car's inner surface will not have any charge. Consider another case where a deep, hollow, metal container is connected to an electroscope. If a positively charged object is lowered into this container, the electroscope deflects, suggesting the presence of electric charges on the container's surface. This condition can be approximated as a charge enclosed inside a hollow conductor. Due to electrostatic equilibrium and Gauss' Law, the conductor's inner surface acquires negative charges. As the net charge inside the conductor is zero, the conductor's surface also acquires a net charge opposite to that of the cavity. Thus, the charges always reside on the surface of a conductor.