Write the formula for the force per unit length between two parallel,current-carrying conducting wires.

(N/A) The force per unit length $f$ between two long,straight,parallel wires carrying currents $I_1$ and $I_2$ separated by a distance $d$ is given by the formula:
$f = \frac{\mu_0 I_1 I_2}{2 \pi d}$
Where:
- $\mu_0$ is the permeability of free space $(4 \pi \times 10^{-7} \ T \cdot m/A)$,
- $I_1$ and $I_2$ are the currents in the two wires,
- $d$ is the perpendicular distance between the wires,
- The force is attractive if the currents are in the same direction and repulsive if they are in opposite directions.