Magnetic force between two parallel conductors?

Question

The hot and neutral wires supplying DC power to a light rail commuter train carry 800 A and are seperated by 75.0 cm. What is the magnitude and direction of the force between 50.0 m of these wires?

Answer 1

From the ref. F/L = µ0*I1*I2/(2πD) = 0.1706667 N/m, where free-space permeability µ0 = 1.256637E-06 N/A^2.

F = 50*F/L = 8.53333 N. When the wires carry current in opposite directions, the wires repel each other.