Magnetic field is produced by wire 1 and current carrying wire 2 lies in magnetic field B1.

The unit length of wire 2 will experience a force, given by

F2 = B1 I2 x 1 =


According to Fleming's left-hand rule, the force on wire 2 acts in the plane of paper perpendicular to wire 2, directed towards wire 1. Similarly, wire 1 also experiences the same force towards wire 2. Thus, both the conducting wires attract each other with the same force F.

One ampere can be defined as the amount of current flowing through two parallel conductors, which are in the same direction or opposite directions, placed at a distance of one metre in free space, and both the wires attract or repel each other with a force of 2 x 10-7 per metre of their lengths.