Parallel Wires ForceMediumQuestion 20205
Question
Two parallel wires 20 cm apart carry 10 A each in opposite directions. Force per unit length between them is (attractive or repulsive?):
- A1×10⁻⁴ N/m, attractive
- B1×10⁻⁴ N/m, repulsiveCorrect
- C2×10⁻⁵ N/m, repulsive
- D2×10⁻⁵ N/m, attractive
Correct answer
1×10⁻⁴ N/m, repulsive
Explanation
F/L = μ₀I₁I₂/(2πd) = 4π×10⁻⁷ × 10 × 10/(2π × 0.2) = 1×10⁻⁴ N/m. Opposite currents → repulsion.