The force between two infinitely long parallel wires is typically measured as the force per unit length (F/L). The equation for this is:
F/L =2πdμ0I1I2
Where:
F/L is the force per unit length, measured in Newtons per meter (N/m).
μ0 (mu-naught) is the permeability of free space, a fundamental physical constant with a value of 4π×10−7 T·m/A.
I1 and I2 are the currents in the two wires, measured in Amperes (A).
d is the perpendicular distance between the two wires, measured in meters (m).
The direction of the force depends on the direction of the currents:
Attraction: If the currents in the two wires flow in the same direction, the wires will attract each other.
Repulsion: If the currents in the two wires flow in opposite directions, the wires will repel each other.