A long neutral aluminum rod is fixed horizontally on an insulating stand
PHYSICS · Multi-part · CBSE · Physics · Electrostatic Potential and Capacitance · Electrostatic Potential and Capacitance
Problem
A long neutral aluminum rod is fixed horizontally on an insulating stand. A small negatively charged plastic rod is slowly brought near the left end of the aluminum rod but never touches it. After a few seconds the far (right) end of the aluminum rod is momentarily connected to ground by a wire that is then removed. Finally the plastic rod is taken far away.
Assume the aluminum rod and the ground are large enough for any induced charges to reside entirely on their outer surfaces.
(a) Describe qualitatively the distribution of charge along the aluminum rod at three distinct moments: (i) just before grounding, (ii) immediately after the grounding wire is removed while the plastic rod is still present, and (iii) after the plastic rod has been taken far away.
(b) Is the net charge of the aluminum rod the same or different in situations (i) and (iii)? Explain your reasoning with reference to the law of conservation of electric charge.
(c) Suppose an identical grounding procedure is performed but the plastic rod is positively rather than negatively charged. Predict and justify the sign of the final net charge left on the aluminum rod once the plastic rod is removed.