Force per unit length,
I1 = I2 = 3.0 A
r = 25 cm (1 m / 100 cm) = 0.25 m
μ0 = 4π × 10-7 T•m/A
Two current-carrying wires are exactly parallel to one another and both carry 3.0 A of current. The two wires are separated by a distance of 25 cm. The current in wire 1 moves down while the current in wire 2 moves up. What is the magnitude of the magnetic force per unit length caused by wire 1 on wire 2? What is the direction of the magnetic force caused by wire 1 on wire 2?