Practice question

**Diamagnetism** exhibits small negative susceptibility χ ≈ -10⁻⁵ to -10⁻⁶, weakly repelled from stronger to weaker field regions, no permanent moment, induced moment opposite to B, present in all materials but dominated by other effects. Superconductor perfect diamagnet with χ = -1, complete field expulsion. B_m = μ₀ M . Given: M = 4 × 10⁵ A m⁻¹ , μ₀ = 4π × 10⁻⁷ . Substitute: B_m = 4π × 10⁻⁷ × 4 × 10⁵ = 1.6π × 10⁻¹ ≈ 0.5 T . Substituting values gives 0.5 T, which matches expected magnitude for this magnetic configuration, confirming dipole field dependence on m/r³ and torque relation τ = m B sinθ.