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A current carrying coil is placed with its axis perpendicular to N-S direction. Let horizontal component of earth's magnetic field be Ho and magnetic field inside the loop is H. If a magnet is suspended inside the loop, it makes angle \[\theta \] with H. Then \[\theta \]=                                                                       [Orissa PMT 2004]

A)            \[{{\tan }^{-1}}\left( \frac{{{H}_{0}}}{H} \right)\]             

B)            \[{{\tan }^{-1}}\left( \frac{H}{{{H}_{0}}} \right)\]

C)            \[\cos e{{c}^{-1}}\left( \frac{H}{{{H}_{0}}} \right)\]         

D)            \[{{\cot }^{-1}}\left( \frac{{{H}_{0}}}{H} \right)\]

Correct Answer: A

Solution :

           In given case H and H0 are perpendicular to each other. From figure \[\tan \theta =\frac{{{H}_{0}}}{H}\]     Þ \[\theta ={{\tan }^{-1}}\left( \frac{{{H}_{0}}}{H} \right)\]