Question

obtain an expression for the torque developed when magnetic dipole is placed in a uniform magnetic field

Answer 1

The force is given as

F = (u.∇).B

where u is the dipole moment and B is the magnetic field strength

In uniform field

F = 0

and u = IA

the torque is given as

τ = u x B = |u||B|sinθ

or

τ = IA.B.sinθ

here θ is the angle between u and B.