When two parallel current carrying wires are kept near to each other, each exerts a force on other. We can think of either one of the wirs as being situated in the magnetic field caused by the other current carrying wire. Hence there results a force between these current carrying conductors. To calculate this force we consider two long straight conductors R and S, carrying currents IR and IS , respectively, and seperated by a distance d. The magnetic field BR , at the location of the conductor S, due to current IR , flowing in conductor R, is given by
Due to this field the force on a length L of the (other) conductor, carrying a current IS , is given by
The force, per unit length, therefore, equals
We represent below the field lines and direction of force, between two parallel current carrying conductors, carrying currents that are (i) LIKE and (ii) UNLIKE, currents.
