calculate force per unit length on a long straight wire carrying vurrent of 4A due to a parallel wire carrying 6A distance between the wire is 3cm

The force per unit length between two current carrying wires separated by a distance ‘r’ is given by,

F/L = µ_oI₁I₂/(2πr)

So, F/L = (4π × 10^-7)(4)(6)/(2 × π × 0.03)

=> F/L = 1.6 × 10^-4 N/m