A point charge is moving in clockwise direction in a circle with constant speed. Consider the magnetic field produced by the charge at a fiexed point P (not at the centre of circle ) on the axis of the circle. Then,

Options

A. it is constant in magnitude only
B. it is constant in direction only
C. it is constant both in direction and magnitude
D. It is constant neither in magnitude nor in direction

Answer

A

Explanation

(a) The point charge moves in circle as shown in Fig.
The magnetic field vectors at a point P on the axis of circle
are `vecB_A and vecB_C` at the instant the point charge is at A and C
respectively, as shown in Fig.

Hence, as the particle rotates in circle, only magnitude of mag-
netic field remains constant at P but its direction changes.