Two identical point charges are fixed 0.60 m apart
PHYSICS · Single correct · A Level · Physics · Fields and their consequences · Fields and their consequences
Problem
Two identical point charges +Q are fixed 0.60 m apart. A small positive charge +q is slowly brought from infinity to a point exactly halfway between them. Which statement best describes the change in the total electric potential energy of the three-charge system?
(a) It decreases because the repulsive force between like charges does positive work on +q, lowering the system's potential energy.
(b) It remains zero because the electric field is zero at the midpoint, so no electric potential exists there.
(c) It increases because the charge is brought into a region of positive electric potential created by the two fixed charges.
(d) It stays the same as at infinity because only the separation of the two fixed charges affects the system’s potential energy.