NCERT Class XII Chapter
Magnetism and Matter
Questions With Solutions

Soln. (a) Work required to turn the dipole, W = MB [cos θi – cos θf]
(i) θi = 0° and θf = 90°
W = 1.5 × 0.22 [cos 0° – cos 90°] = 0.33 J
(ii) θi = 0° and θ = 180°, W = 1.5 × 0.22 [cos 0° – cos 180°] = 0.66 J
(b) Torque when θ = 90°, τ1 = MB sin 90° = 0.33 N m
Torque when θ = 180°, τ2 = MB sin 180° = 0