PHYSICS · Multi-part · AP · Physics C: Electricity and Magnetism · Conductors and Capacitors · Conductors and Capacitors
Problem
Two identical isolated conducting spheres, A and B, are each mounted on insulating stands. Sphere A initially carries a charge of +10μC, whereas sphere B is neutral. The following operations are performed in order:
1. The spheres are connected by a long thin metal wire and left undisturbed until they reach electrostatic equilibrium.
2. The wire is disconnected, after which sphere A alone is momentarily connected to Earth and then isolated again.
Throughout the process the spheres remain well separated so that no direct charge flows between a sphere and any object except along the explicitly mentioned conducting paths.
(a) Immediately after step 1 but before the wire is removed, determine the charge on each sphere. Explain your reasoning.
(b) After the wire is disconnected but before grounding in step 2, state the charge on each sphere.
(c) During the grounding of sphere A in step 2, indicate the direction of electron flow between sphere A and Earth and compute the amount of charge that moves.
(d) After all connections have been removed, give the final charge (magnitude and sign) on each sphere. Provide a clear justification that traces conservation of charge through every stage.