What This Calculator Does
Two parallel wires carrying electric current exert a magnetic force on each other — attractive if the currents flow in the same direction, repulsive if they flow in opposite directions. This calculator finds that force from the two currents, their separation distance, and the length of wire involved.
The Formula
Ampere’s force law gives the force per unit length between two long parallel wires as F/L = μ0 × I1 × I2 ÷ (2πd), where μ0 = 4π × 10-7 T·m/A is the permeability of free space, I1 and I2 are the currents in amps, and d is the separation in meters. Multiplying by the wire length L gives the total force.
- Same direction currents attract the wires toward each other.
- Opposite direction currents push the wires apart.
This is the standard physics formula for idealized straight, thin, parallel wires, used for general physics education and planning purposes; real conductors with finite thickness or non-parallel geometry will show small deviations from this ideal result.