Question

A bar magnet of magnetic moment $200A-m^2$ is suspended in a magnetic field of intensity $0.25N/A-m$. The couple required to deflect it through ${30}^{\circ }$ is

• A. 50 N - m
• B. 25 N - m
• C. 20 N - m
• D. 15 N - m

Answer 1

The correct option is B 25 N - m

$\tau =MBsin\theta$
$\tau =200\times 0.25\times sin{30}^{\circ }=25N\times M$