A thin diamagnetic rod is placed vertically between the poles of an electromagnet. When the current in the electromagnet is switched on, then the diamagnetic rod is pushed up, out of the horizontal magnetic field. Hence the rod gains gravitational potential energy. The work required to do this comes from

If $$\theta $$₁ and $$\theta $$₂ be the apparent angles of dip observed in two vertical planes at right angles to each other, then the true angle of dip $$\theta $$ is given by

A 250-turn rectangular coil of length 2.1 cm and width 1.25 cm carries a current of 85 $$\mu $$A and subjected to a magnetic field of strength 0.85 T. Work done for rotating the coil by 180^o against the torque is

A bar magnet is hung by a thin cotton thread in a uniform horizontal magnetic field and is in equilibrium state. The energy required to rotate it by 60^o is W. Now the torque required to keep the magnet in this new position is