A direct current passes upwards through a rectangular plane containing a long, straight vertical wire as shown.

Draw on this

On the diagram, sketch the magnetic field caused by the current in the wire.

A second, parallel vertical wire is suspended nearby and is free to move.

• When direct currents pass in the same direction through both wires, they move towards each other.
• When the current in one of the wires is reversed, they move apart.

Explain why the wires move in this way.