Question

A bar magnet of magnetic moment $200A-m^2$ is suspended in a magnetic field of intensity 0.25 NA - m . The couple required to deflect it through 30${}^0$ is

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

Answer 1

Answer: (B)

25 N-m

$m=200A{m}^2$
$B=0.25T$
$\theta ={30}^0$
$z=mBsin30$
$200\times 0.25\times \frac{1}{2}$
$z=25N.m$