The torque on a bar magnet due to the earth's magnetic field is maximum when the axis of the magnet is

Options

A. perpendicular to the field of the earth
B. Parallel to the vertical component of the earth's field
C. At an angle of `33^(@)` with respect to the `N-S` direction
D. Along the North-South `(N-S)` direction

Answer

A

Explanation

Torque on a bar magnet in earth's magnetic field `(B_(H))` is `"tau"=MB_(H) sintheta`. `tau` will be maximum if `sintheta` = maximum i.e., `theta=90^(@)`. Hence, axis of the magnet is perpendicular to the field of earth.