Question Detail

The magnetic field (B) outside a long straight current-carrying wire at a distance 'r' is given by the formula: B = (μ₀I) / (2πr).We need to find the current (I). Rearranging the formula: I = (B * 2πr) / μ₀.Given:B = 20 μT = 20 × 10-6 Tr = 120 mm = 0.120 mμ₀ = 4π × 10-7 Tm/AI = (20 × 10-6 T * 2π * 0.120 m) / (4π × 10-7 Tm/A)I = (20 × 10-6 * 0.24π) / (4π × 10-7)I = (20 * 0.24 * 10-6) / (4 * 10-7)I = (4.8 × 10-6) / (4 × 10-7)I = (4.8 / 4) × 10(-6 - (-7)) = 1.2 × 101 = 12 A.