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 and opposite to the force on wire b due to wire a. Using the right-hand rule one can show the following:
Parallel wires with current flowing in the same direction, attract each other.
Parallel wires with current flowing in the opposite direction, repel each other.