A current carrying circular coil, suspended freely in a uniform external magnetic field orients to a position of stable equilibrium. In this state :      

Given Data:

A current carrying circular coil, suspended freely in a uniform external magnetic field orients to a position of stable equilibrium.   

Formula Used:

$\overrightarrow{\tau }=0=\overrightarrow{M}\times \overrightarrow{B}$

Detailed Solution:

In equilibrium torque is zero.

$$\begin{gathered} \overrightarrow{\tau }=0=\overrightarrow{M}\times \overrightarrow{B} \\ =ni\overrightarrow{A}\times \overrightarrow{B} \\ =niAB\sin \theta \end{gathered}$$

So,$\sin \theta =0\Rightarrow \theta =0^0$

So, the plane of the coil is normal to the field.

Hence, the correct option is A.