Practice question

**Magnetic field of bar magnet** follows inverse cube law B ∝ m/r³, unlike inverse square for electric dipole. Given B at distance r, moment m = B r³/(μ₀/4π) for equatorial, m = B r³/(2·μ₀/4π) for axial, enabling moment extraction from measured field. Ferromagnetic materials have magnetic domains that spontaneously align, resulting in a large positive susceptibility ( chi gg 1 ). This strong magnetization occurs due to cooperative interactions among atomic magnetic moments, distinguishing them from other materials. Substituting values gives Large and positive, which matches expected magnitude for this magnetic configuration, confirming dipole field dependence on m/r³ and torque relation τ = m B sinθ.