Question

$M$ and $M \sqrt{3}$ are the magnetic dipole moments of the two magnets which are joined to form a cross figure. The inclination of the system with the field, if their combination is suspended freely in a uniform external magnetic field $B$ is

• A. $\theta=30^{\circ}$
• B. $\theta=45^{\circ}$
• C. $\theta=60^{\circ}$
• D. $\theta=15^{\circ}$

Answer 1

Answer: (C)

In equilibrium, $\tau_{1}=\tau_{2}$
$M B \sin \theta=\sqrt{3} M B \sin \left(90^{\circ}-\theta\right)$
$\therefore \tan \theta=\sqrt{3} $
$\Rightarrow \theta=60^{\circ}$