Attraction of two wires

A current-carrying wire acts as a source of magnetic field. A second wire will feel a force from the magnetic field of the first one. The force on wire a due to wire b will always be equal in magnitude and opposite in direction to the force on wire b due to wire a (Newton's third law). Using the right-hand rule you can show the following:

  1. Parallel wires with currents flowing in the same direction, attract each other.

  2. Parallel wires with currents flowing in the opposite direction, repel each other.

You can calculate the force, since you know how to find the B-field produced by a current-carrying wire, and you know how to find the force on a current-carrying wire in a B-field.

Examples       Magnetic field sources index        Lecture index