Question

The radius of a circular coil is 0.05 m and number of turns are 100. If 0.1 A current is flowing through it, then how much work will be done to rotate it 180° against the perpendicular external magnetic field of 1.5 T? Initially the plane of coil is perpendicular to magnetic field.

Answer 1

Given, r = 0.05 m; M = 100; I = 0.1 A;
B = 1.5T; θ1 = 0°; θ2 =180°
Work done W = – MB (cosθ2 – cosθ1)
= -NIAB(cosθ2 – cosθ1)
= -NIπr2B(cosθ2 – cosθ1)
= -100 × 0.1 × 3.14 × (0.05)2 × 1.5 × (cos180°- cos 0°)
= 2 × 100 × 0.1 × 3.14 × (0.05)2 × 1.5
= 0.236 J