Worked example: A galvanometer has N = 200 turns, A = 5 cm², B = 0.3 T, spring constant k = 2 × 10⁻⁶ N·m/rad, coil resistance G = 120 Ω. (a) Find current sensitivity. (b) Full-scale current for 90° (π/2 rad)? (c) Voltage sensitivity? Step 1: Si = NBA/k = (200 × 5 × 10⁻⁴ × 0.3)/(2 × 10⁻⁶) = (0.03)/(2 × 10⁻⁶) = 15,000 rad/A = 15 rad/mA — enormous, as expected of a sensitive meter. Step 2: Ig = φ/Si = (π/2)/15000 = 1.047 × 10⁻⁴ A ≈ 0.105 mA full scale. Step 3: Sv = Si/G = 15000/120 = 125 rad/V. Check: at full scale V = Ig·G = 0.105 mA × 120 Ω = 12.6 mV, and φ = Sv·V = 125 × 0.0126 = 1.575 rad = π/2 ✓. Design moral: sensitivity is geometry (NBA) fighting the spring (k).