Practice question

**Geomagnetic field** arises from outer core dynamo, field lines emerge near geographic south pole. Understanding D and I allows conversion between geographic and magnetic coordinates, with B_H = B cos(inclination) used in experiments with tangent galvanometer. M = chi H . Given: chi = 4 × 10⁻⁴ , H = 2000 A m⁻¹ . M = 4 × 10⁻⁴ × 2000 = 0.8 A m⁻¹ . Substituting values gives 0.8 A m⁻¹, which matches expected magnitude for this magnetic configuration, confirming dipole field dependence on m/r³ and torque relation τ = m B sinθ.