Electromagnets

Learning Objectives:

Describe how to make an electromagnet

-Describe how to change the strength of electromagnet

The magnetic field around a wire

A wire with an electric current flowing through it has a magnetic field around it,You can investigate the field and with a plotting compass.The field lines are circles.

Making an electromagnet

You can make a circular loop of wire and pass a current through it.The magnetic field lines at the center of the loop are straight.

The magnetic field around a single loop isn’t very strong.If you put lots of loops together to make a coil the field is much stronger.This is an electromagnet.The shape of the magnetic field is just like the shape of the magnetic field around a bar magnet.

You can turn an electromagnet on and off by turning the current on and off.The magnetic field is only produced when the current is flowing in the wire.

Using a core

Electromagnets usually have a magnetic material in the center of the coil,called a core.This makes the electromagnet much stronger.Most cores are made of iron.Iron is easy to magnetize but loses its magnetism easily.

Steel is hard to magnetize but keeps its magnetism.If you had a steel core in an electromagnet you could not turn the electromagnet off,because the steel would still be magnetic.

How do I make