Electromagnets - How can electricity make a magnet?
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An electromagnet from inside a stereo speaker

About 200 years ago, people figured out another way to make magnets, so that you didn't need a lodestone. This way you could also make much stronger magnets, and you could turn the magnets on and off.

The new way is an electromagnet, or a magnet that works by using electricity to create a magnetic field in a piece of iron.

When you hook up a copper wire to a battery, electrons begin to flow through the wire, moving from atom to atom, from one end of the battery to the other, trying to even out the negative and positive charges at each end of the battery. This makes a circle of electrons just like the circle of electrons inside an iron atom, and, just like the iron atom, that's a magnet.

To make the iron atoms strong enough to be a useful magnet, you have to line up a lot of them all going the same way, and it's the same with an electromagnet - you have to make lots of copper wire circles all going the same way. If you wrap these coils around something made of iron, the coils will act like a lodestone and make that iron into a magnet. If you use thousands of coils of wire and a big piece of iron, you can make a very strong magnet that can pick up cars and huge machines.

But tiny electromagnets are also very useful, because you can turn them on and off by connecting or disconnecting the batteries. Alternating magnets power stereo speakers, hold fire doors open, and are inside all electric motors, like in a hair dryer or a washing machine.

More about magnets
Learn by Doing - Electromagnets
Learn by Doing - Magnets
The invention of the compass
More about Electricity

Another project - Build an Electric Motor
Or Another Project - Build a Circuit Board

Bibliography and further reading about magnets and electricity:

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Professor Carr

Karen Eva Carr, PhD.
Assoc. Professor Emerita, History
Portland State University

Professor Carr holds a B.A. with high honors from Cornell University in classics and archaeology, and her M.A. and PhD. from the University of Michigan in Classical Art and Archaeology. She has excavated in Scotland, Cyprus, Greece, Israel, and Tunisia, and she has been teaching history to university students for a very long time.

Professor Carr's PSU page

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Now that the weather's nice, try some of these outdoor activities! How about bicycle polo, or archery for a Medieval Islam day? Or kite flying or making a compass for a day in Medieval China? How about making a shaduf for a day in Ancient Egypt? Holding an Ancient Greek Olympic Games or a medieval European tournament? Building a Native American wickiup?