Practice question

**Magnetic properties** μ_r = 400 indicates 400 times vacuum permeability, so B enhanced 400 times for same nI. H = nI (A/m) for solenoid, M = χ H, B = μ₀(H+M) links microscopic magnetization to macroscopic field. Relative magnetic permeability μ_r = 1 + chi . Given: chi = 0.001 . Substitute: μ_r = 1 + 0.001 = 1.001 . Substituting values gives 1.001, which matches expected magnitude for this magnetic configuration, confirming dipole field dependence on m/r³ and torque relation τ = m B sinθ.