Electromagnets

Electromagnets

A long conductor can be wrapped to form a coil. If a voltage is placed across the coil then the magnetic field from the current is concentrated in one direction This field lines up with the axis of the coil. The coil can be wrapped around a metal core. The core helps the magnetic field line up.

Fig. 4 An electromagnet

This setup is called an electromagnet. By convention, the direction of the magnetic field is from North to South. The coil is said to be energized when a voltage is placed across it. When the coil is energized the core is magnetized and acts just like a permanent magnet. When the coil is de-energized the core loses its magnetism.