Question

A magnet of magnetic moment $50\, \hat{i} \,A\, m ^{2}$ is placed along the $x$ -axis in a magnetic field $\vec{B}=(0.5 \hat{i}+3.0 \hat{j}) T$. The torque acting on the magnet is

• A. $175 \,\hat{k} \,N \,m$
• B. $150 \,\hat{k}\, N\, m$
• C. $75\,\hat{k}\, N\, m$
• D. $25 \sqrt{37} \,\hat{k}\, N\, m$

Answer 1

Answer: (B)

$\vec{\tau}=\vec{M} \times \vec{B} \Rightarrow \vec{\tau}$
$=50 \hat{i} \times(0.5 \hat{i}+3 \hat{j})$
$=150(\hat{i} \times \hat{j})=150\, \hat{k}\, N\, m$