Two parallel wires are separated by 6.65 cm, each carrying 3.25 a of current in the same direction. (a) what is the magnitude of the force per unit length between the wires?

The magnitude of the force per unit of lenght between the wires are of  F/L= 3.17 * 10⁻⁵ N/m.

Explanation:

d=0.0665m

I1=I2= 3.25A

μo= 4π * 10⁻⁷ N/A²

F/L= (μo * I1 * I2) / (2π * d)

F/L= 3.17 * 10⁻⁵ N/m

that would be because of both gravity and friction. so     c