Worked example: A circular loop (radius 5 cm, 200 turns) carries 1.5 A in Earth's field (B = 30 μT). (a) Find m. (b) Maximum torque? (c) Energy difference between aligned and anti-aligned? Step 1: A = π(0.05)² = 7.854 × 10⁻³ m². m = NIA = 200 × 1.5 × 7.854 × 10⁻³ = 2.356 A·m². Step 2: τmax = mB = 2.356 × 30 × 10⁻⁶ = 7.07 × 10⁻⁵ N·m — small, but galvanometers detect far smaller. Step 3: U = −m·B: aligned U = −mB, anti-aligned U = +mB; difference ΔU = 2mB = 1.414 × 10⁻⁴ J. A freely pivoted loop would oscillate and settle aligned — a compass in principle, though friction dominates at this scale.