The force between two parallel currents I1 and I2 separated by a distance r, has a magnitude per unit length given by Fl=μ0I1I22πr. The force is...The force between two parallel currents I1 and I2 separated by a distance r, has a magnitude per unit length given by Fl=μ0I1I22πr. The force is attractive if the currents are in the same direction, repulsive if they are in opposite directions.
This field is uniform along wire 2 and perpendicular to it, and so the force F2 it exerts on wire 2 is given by F=IlBsinθ with sinθ=1: \[F_{2} = I_{2}lB_{1}.\label{22.11...This field is uniform along wire 2 and perpendicular to it, and so the force F2 it exerts on wire 2 is given by F=IlBsinθ with sinθ=1: F2=I2lB1. By Newton’s third law, the forces on the wires are equal in magnitude, and so we just write F for the magnitude of F2. (Note that F1=−F2.) Since the wires are very long, it is convenient to think in terms of F/l, the force per unit length.
