Question

Two bar magnets with magnetic moments $2 M$ and $M$ are fastened together at right angles to each other at their centres to form a crossed system, which can rotate freely about a vertical axis through the centre. The crossed system sets in earth's magnetic field with magnet having magnetic moment $2 M$ making and angle $\theta$ with the magnetic meridian such that

• A. $\theta=\tan ^{-1}\left(\frac{1}{\sqrt{3}}\right)$
• B. $\theta=\tan ^{-1}(\sqrt{3})$
• C. $\theta=\tan ^{-1}\left(\frac{1}{2}\right)$
• D. $\theta=\tan ^{-1}\left(\frac{3}{4}\right)$

Answer 1

Answer: (C)

$\Rightarrow \tan \theta=\frac{M}{2 M}=\frac{1}{2}$
$\Rightarrow \theta=\tan ^{-1}=\frac{1}{2}$