A coil of wire, or solenoid, consists of a wire coiled up into a spiral shape. When an electric current flows, the shape of the magnetic field is very similar to the field of a bar magnet.

A coil of wire, or solenoid, consists of a wire coiled up into a spiral shape. When an electric current flows, the shape of the magnetic field is very similar to the field of a bar magnet.

When an electric current passes through a metal wire, a magnetic field forms around that wire (see diagram at right). Likewise, a wire passing through a magnetic field creates an electric current ...