Two short bar magnets of dipole moments M and M 3 are joined at right angles to form a cross as depicted in the figure. The value of θ for which the system remains in equilibrium in a uniform external magnetic field B , is

Step-by-step solution

Torque τ acting on magnet (1), τ 1 = MBsin ⁡ θ Similarly, τ 2 = 3   MBsin ⁡ θ But for equilibrium, τ 1 = τ 2 ∴      MBsin ⁡ θ =   3   MBcos ⁡ θ   tan ⁡ θ = 3   = tan ⁡ 60 ° ∴      θ = 60 °