Question

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

The correct option is B $150\hat{k}N-m$

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