Two parallel wires 1 m apart carry currents of 1 A and 3 A respectively in opposite directions. The force per unit length acting between two wires is
6 × 10–5 Nm–1 repulsive
6 × 10–7 Nm–1 repulsive
6 × 10–5 Nm–1 attractive
6 × 10–7 Nm–1 attractive