Two short bar magnets of dipole moments $M$ and $M \sqrt{3}$ 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

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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 °

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