Discussion Forum

A rectangular loop of sides 10 cm and 5 cm carrying a current I of 12A is placed in different orientations as shown in the figures below.

   If there is a uniform magnetic field of 0.3 T in the positive z-direction in which orientations the loop would be in (i) stable equilibrium and (ii)  unstable equilibrium?

Answer:

Explanation:

Since B is uniform only torque acts on a current-carrying loop.

  As,    $\tau=M\times B$ 

  $\Rightarrow$          $|\tau|=|M||B|\sin\theta$

 For orientation shown in (b)  $\theta=0^{0},\tau=0$

             (stable equilibirum)

  and for (d)  $\theta=\pi,\tau=0$  (unstable equilibium)