Practice question

**Earth's magnetism** approximated as dipole inclined to rotation axis, magnetic declination is angle between geographic north and magnetic north, inclination or dip angle is angle between total field and horizontal. Horizontal component B_H = B cosδ, vertical B_V = B sinδ, δ dip angle, B_H ≈ 3-4×10⁻⁵ T in India. tau = m B sinθ . Given: m = 0.2 A m² , B = 0.8 T , θ = 45° , sin 45° = (1/√(2)) ≈ 0.707 . tau = 0.2 × 0.8 × 0.707 ≈ 0.11312 N m ≈ 0.11 N m . Substituting values gives 0.11 N m, which matches expected magnitude