Question

A bar magnet of the moment $\overset{ \rightarrow }{M}=\hat{i}+\hat{j}$ is placed in a magnetic field induction $\overset{ \rightarrow }{B}=3\hat{i}+4\hat{j}+4\hat{k}$ . The torque acting on the magnet is

• A. $4\hat{i}-4\hat{j}+\hat{k}$
• B. $\hat{i}+\hat{k}$
• C. $\hat{i}-\hat{j}$
• D. $\hat{i}+\hat{j}+\hat{k}$

Answer 1

Answer: (A)

When bar magnet is palced in external magnetic field it experiences torque.
$\overset{ \rightarrow }{\tau}=\overset{ \rightarrow }{M}\times \overset{ \rightarrow }{B}$
$\overset{ \rightarrow }{\tau}=$ $4\hat{i}-4\hat{j}+\hat{k}$