Force between Two Parallel Current Carrying Conductors #8211; When two long straight conductors carrying current I<sub>1</sub> and I<sub>2</sub> are placed parallel at a distance of a from each other, then a mutual force of attraction acts between them which is given alongside. Force per unit length, F/l = μ<sub>0</sub>/4πtimes;2I<sub>1</sub> I<sub>2</sub>/a N/m