Four separate pairs of point charges are arranged in otherwise empty space
PHYSICS · Multi-part · A Level · Physics · Fields and their consequences · Fields and their consequences
Problem
Four separate pairs of point charges are arranged in otherwise empty space. Each pair contains only the two charges listed, separated by the same fixed distance d. The magnitudes of all charges are equal to q. The four pairs are:
Pair I +q and +q
Pair II −q and −q
Pair III +q and −q
Pair IV +2q and −q (charges still separated by d)
Ignore all interactions between different pairs.
(1) Rank the electric potential energy of the four listed pairs from the greatest positive value to the most negative value. Express your answer in the format I > II > III > IV, using “=” if any pairs have equal potential energy.
(2) Describe the reasoning that supports your ranking, specifically addressing the roles played by (i) the product of the charges and (ii) any difference in magnitude of the individual charges.