Electromagnet

A solenoid with an iron core is called an electromagnet.

Soft iron is used as the core of an electromagnet. A current through a surrounding coil creates a magnetic field. This aligns domains in the iron, magnetising the core and making the electromagnet stronger.

The solenoid's field magnetises the iron, whose magnetic field adds to that of the coil. This produces a strong electromagnet. Soft iron is useful because it becomes magnetised when the current is on but readily loses its magnetism when the current is switched off.

A solenoid containing an iron core is an electromagnet. Its great advantage over a permanent magnet is control: switching the current on produces the magnetic effect, while switching it off removes or greatly reduces it. Changing the current can also change the field strength, and reversing the current reverses the poles.