Question

The magnetic moment of a magnet is $0.25A-m^2$. It is suspended in a magnetic field of intensity $2\times {10}^{-5}T$. The torque acting on it when deflected by ${30}^0$ from the magnetic field is :

• A. $2.5\times {10}^{-5}N-m$
• B. $2.5\times {10}^{-6}N-m$
• C. $1.25\times {10}^{-6}N-m$
• D. $1.25\times {10}^{-5}N-m$

Answer 1

Answer: (B)

$2.5\times {10}^{-6}N-m$

Magnetic moment, $M=0.25A-m^2.$

Magnetic field, $B=2\times {10}^{-5}T$

Torque, $\tau =MBsin\theta$

$\tau =0.25\times 2\times {10}^{-5}\times sin{30}^o$

=$2.5\times {10}^{-6}N-m$.