Question

Suppose that the sphere of a Van de Graaff generator gathers a charge. Then the motor is turned off and the sphere is allowed to reach electrostatic equilibrium. The charge

• A. resides both on its surface and throughout its volume
• B. resides mostly inside the sphere and only emerges outside when touched
• C. resides only on the surface of the sphere
• D. None of these

Answer 1

The correct option is C resides only on the surface of the sphere

This is because of the following reason:
Electrostatic equilibrium is the condition established by the charged conductors in which the excess charge has optimally distanced itself so as to reduce the total amount of impulsive forces. Given that the sphere of a Van De Graff generator gathers a charge. Then the motor is turned off and the sphere is allowed to reach equilibrium. When a "closed" conductor becomes charged, the excess of charge accumulates on the outer surface of the conductor. Since the generator has been turned off, there is no source of charge inside it. All the charge resides on the outside of dome i.e, on the surface of the sphere.