question_answer

At some location on earth the horizontal component of earth's magnetic field is \[18\times {{10}^{-6}}T.\] At this location, magnetic needle of length 0.12 m and pole strength 1.8 A m is suspended from its mid-point using a thread, it makes \[45{}^\circ \] angle with horizontal in equilibrium. To keep this needle horizontal, the vertical force that should be applied at one of its ends is:

A) \[3.6\times {{10}^{-5}}N\]

B) \[1.8\times {{10}^{-5}}N\]

C) \[1.3\times {{10}^{-5}}N\]

D) \[6.5\times {{10}^{-5}}N\]