Question

A dipole of magnetic moment $\overrightarrow{m}=30\hat{j}$A $m^2$ is placed along the y-axis in a uniform magnetic field $\overline{B}=(2\hat{i}+5\hat{j})$T. The torque acting on it is?

• A. $-40\hat{k}$N m
• B. $-50\hat{k}$N m
• C. $-60\hat{k}$N m
• D. $-70\hat{k}$N m

Answer 1

The correct option is C $-60\hat{k}$N m

Given that,

Magnetic moment of a dipole, $\overrightarrow{m}=30\hat{j}A{m}^2$

Magnetic field, $\overrightarrow{B}=(2\hat{i}+5\hat{j})T$

Torque acting on the dipole , $\overrightarrow{\tau }=\overrightarrow{m}\times \overrightarrow{B}$

$⟹\overrightarrow{\tau }=30\hat{j}\times (2\hat{i}+5\hat{j})=-60\hat{k}Nm$