A magnet is suspended by a vertical string attached to its middle point. Find the position in which the magnet can stay in equilibrium. The horizontal component of the earth's magnetic field ` = 25 mu T` and its vertical component `40 mu T`. Assume that the string makes contact with the magnet only at a single point.

Explanation

The magnetic field of earth is in the north-south plane (magnetic meridian) making an angle `theta` with the horizontal such that` `tantheta = B_V/B_H = 40/25`
or, `theta = 58^@`.
As the tension and the force of gravity act through the centre, their torque about the centre is zero. To make the net torque acting on the magnet zero, it must stay in the direction of the resultant magnetic field. Hence, it stays in the magnetic meridian making an angle of `58^@` with the horizontal.