Answer: r = 1.33 × 10^-5 mm
Explanation: The force per unit length of 2 current carrying conductor is given by the formulae below.
F/L = (u×I1×I2) /(2πr)
Where F/L = force per unit length = 7.73×10^-5mm = 0.0775 mm.
I1 = current on the first conductor = 4.27A
I2 = current on the second conductor = 1.19A
r = distance between both conductors.
u = permeability of free space = 1.25×10^-6
By substituting parameters, we have that
0.0775 = 1.25×10^-6 × 4.27 × 1.19/ 2πr
By cross multiplication
0.0775 ×2πr = 1.25×10^-6 × 4.27 × 1.19
r = 1.25×10^-6 × 4.27 × 1.19/ 0.0775 ×2π
r = 0.00000635162 / 0.0775 ×2π
r = 1.33 × 10^-5 mm