Uses of electromagnetism
Lifting scrap metal
Electromagnets can be usefully employed to move scrap metal from one place to another.
When the current is switched off the magnet losses its magnetism and the car falls back to the ground.
See below for a typical cross section through an industrial electromagnetic lifting device:
Electromagnets can be turned off. Used for moving scrap metal from one place to another. The crane operator can lower a large disc onto a pile of scrap and then switch on the electromagnet. The large disc and the scrap can be lifted. The scrap metal can be dropped anywhere once the electrical supply to the electromagnet has been switched off.
Electromagnetic electric bells have been used for many years.
When the switch is on, current proceeds to flow through the electromagnet. A magnetic field is generated around the coil which, in turn, attracts the soft iron. Attached to the soft iron is a hammer which strikes the bell. As soon as the bell is struck the electrical circuit is broken and the soft iron returns to rest on the threaded contact. The current proceeds to flow through the electromagnet. This process keeps repeating until the circuit is switched off.
Electromagnets are used extensively in loudspeakers.
The frequency of the vibrations of sound can be transported electrically as changes in electrical flow.
A loudspeaker can take these changing electrical flows through an electromagnet attached to a cone. Changes in the current flow alters the strength of attraction to the permanent magnet, moving the electromagnetic coil in and out. Soft quiet sounds move slowly, loud harsh sounds move violently and strongly. This results in a vibration of the speaker cone which will create sound waves out to our ear.