Question

A magnetised needle of magnetic moment 4.8 × 10^-2 Am² is placed at 30° with the direction of uniform magnetic field of magnitude 3 × 10^-2 T. What is the torque acting on the needle?

Options

• 7.2 × 10^-1 N-m

• 7.2 × 10^-2 N-m

• 7.2 × 10^-4 N-m

• 7.2 × 10^-3 N-m

Answer 1

7.2 × 10^-4 N-m

Explanation:

Here, M = 44.8 × 10^-2 Am² 

θ = 30°, B = 3 × 10^-2 T

As τ = MB sin θ

τ = 4.8 × 10^-2 × 3 × 10^-2 sin 30°

τ = 7.2 × 10^-4 N-m