Practice question

**Core magnetization** M = (μ_r -1)nI, so B = μ₀(nI + M). High μ_r materials like soft iron increase B dramatically for same nI, used in electromagnets, with μ_r up to 5000, enabling strong fields with low current. tau = m B sinθ . Given: m = 0.7 A m² , B = 0.6 T , θ = 30° , sin 30° = 0.5 . tau = 0.7 × 0.6 × 0.5 = 0.21 N m . Substituting values gives 0.21 N m, which matches expected magnitude for this magnetic configuration, confirming dipole field dependence on m/r³ and torque relation τ = m B sinθ.