Question

A current carrying coil is subjected to a uniform magnetic field. The coil will orient so that its plane becomes

• A. inclined at 45${}^o$ to the magnetic field
• B. inclined at any arbitrary angle to the magnetic field
• C. parallel to the magnetic field
• D. perpendicular to magnetic field

Answer 1

The correct option is D perpendicular to magnetic field

$\tau =(\overrightarrow{M}\times \overrightarrow{B})$, where $|\overrightarrow{M}|=i.A$

$=MBsin\theta$
where
$\theta$ is angle between Magnetic moment & $\overrightarrow{B}$.
For $\theta =0\overrightarrow{\tau }=0$ & coil is in stable equilibrium.
Hence plane of coil must be perpendicular to magnetic field.