The force of interaction between two co-axial current loops having radii R & r (r<<R), separated by a distance x carrying currents I₁ & I₂
respectively is given by the expression $\mathrm{F}=\frac{{\left.{\mathrm{N\mu }}_0{\mathrm{\pi R}}^2{\mathrm{r}}^2\right|}_1{\mathrm{l}}_2\mathrm{x}}{2{\left({\mathrm{R}}^2+{\mathrm{x}}^2\right)}^{\frac{5}{2}}}.\mathrm{Find}\text{'} \mathrm{N} \text{'}$