99 Percentile Qs Bank for JEE MainPhysicsMagnetic Properties of Matter
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
Options
- Aθ = 30 °
- Bθ = 45 °
- Cθ = 60 °
- Dθ = 15 °
Correct answer
C. θ = 60 °
Step-by-step solution
Torque τ acting on magnet (1), τ 1 = M B sin θ Similarly, τ 2 = 3 M B sin θ But for equilibrium, τ 1 = τ 2 ∴ M B sin θ = 3 M B cos θ tan θ = 3 = tan 60 ° ∴ θ = 60 °