Question

A flat coil carrying a current has a magnetic moment $\overrightarrow{\mu }$. It is placed in a magnetic field $\overrightarrow{B}$. The torque on the coil is $\overrightarrow{\tau }$

• A. $\overrightarrow{\tau }=\overrightarrow{\mu }\times \overrightarrow{B}$
• B. $\overrightarrow{\tau }=\overrightarrow{B}\times \overrightarrow{\mu }$
• C. $|\overrightarrow{\tau }|=\overrightarrow{\mu }\cdot \times \overrightarrow{B}$
• D. $\overrightarrow{\tau }$ is perpendicular to both $\overrightarrow{\mu }$ and $\overrightarrow{B}$.

Answer 1

Answer: (A), (D)

$\overrightarrow{\tau }=\overrightarrow{\mu }\times \overrightarrow{B}$
$\overrightarrow{\tau }$ is perpendicular to both $\overrightarrow{\mu }$ and $\overrightarrow{B}$.

The magnetic moment is defined as a vector relating the aligning torque on the object from an externally applied magnetic field to the field vector itself. The relationship is given by:

$\tau =\overrightarrow{\mu }\times \overrightarrow{B}$

where $\tau$ is the torque acting on the dipole and $B$ is the external magnetic field, and $\mu$ is the magnetic moment. Direction of torque is given by the right hand rule.