Question

Magnetic fields at two points on the axis of a circular coil at a distance of 0.05 m and 0.2 m from the centre are in the ratio 8 : 1. The radius of coil is ____.

(1) 0.2 m

(2) 0.1 m

(3) 0.15 m

(4) 1.0 m

Answer 1

Correct option is (2) 0.1 m

We know, the magnetic field on the axis of a current carrying circular ring is given by