Question Detail
Question
An equipotential surface is defined as a surface where the force must be perpendicular to the displacement. This implies that if a charge q is moved along an arc of a circle centered on a charge Q, the work done is zero because:
Correct Answer
Option B is the correct answer.
Detailed Explanation
Page 15-16 states: 'Another conclusion we can draw is that if we move a charge q long an arc of a circle centred on the charge Q, or indeed along a sphere centred on Q, then the work done is zero, since the radius of the sphere is constant. This means that the force must be perpendicular to the displacement.' This condition (force perpendicular to displacement) is what defines zero work.
Hint
Work done is zero when the force is perpendicular to the displacement. Consider the definition of an equipotential surface and the force direction.