Question

What is the work done by a magnetic field on moving a charge? Give reason.

Answer 1

When a charge (q) moves in a magnetic field (B) with velocity (v) the Lorentz force on the charge is given by,

F = q(v × B) [bold letters denote vector quantity]

That is, the direction of F is perpendicular to the motion of the charge.

Since, F and displacement are perpendicular the work done by the force is zero.