PHYSICS · Single correct · A Level · Physics · Fields and their consequences · Fields and their consequences
Problem
A point charge +Q is fixed at the origin. Four points are chosen: A(0,5cm,0), B(5cm,0,0), C(0,−5cm,0) and D(0,0,5cm). A small test charge is moved along two different paths:
(i) from A to C along a semicircular arc of radius 5cm in the xy-plane,
(ii) from B to D along the straight line joining them.
Which one of the following statements about the work done by an external agent is correct?
(a) Work is non-zero and equal in magnitude for paths (i) and (ii).
(b) Work is zero in both paths (i) and (ii).
(c) Work is zero in path (i) but non-zero in path (ii).
(d) Work is non-zero in path (i) but zero in path (ii).