We know that an electric current is formed when electrons flow through a conductor, such as a piece of metal wire. When a current flows through a wire a magnetic field is produced. The magnetic field that surrounds a current-carrying conductor can be demonstrated by placing magnetic compasses around a wire. The animation on the right shows how the needles are deflected in response to the strong magnetic field created by the current. The needles align themselves with the magnetic field produced by the current and show it to be a pattern of concentric circles about the wire.