- Virginia Johnson
What do the Earth, electric motors, and your computer all have in common?
These things are all influenced by magnets.
The Earth has a liquid metal core that acts like a bar magnet. It gets its magnetism from being near electrical currents beneath the surface. Because the Earth is not perfectly shaped, every so often the direction of the field will change. Scientists have found evidence that this has occurred at least 171 times over the past 71 million years. How do they know that? Magnets!
When magnetic stones were laid down, they naturally aligned their magnetism with whatever was the magnetic field of the time. A lava flow would cement these rocks in place. The change in the magnetism was steady enough to prove a pattern and teach us the way the Earth has changed through time. According to studies done in the past 150 years, the magnetic field continues to change. This time it’s fading out as it gets ready to do another “flip. Not to worry; this probably won’t happen for generations, and the Earth has survived it before.
The Earth is believed to have a solid center about the size of the moon. Just outside of that is a churning molten metal liquid. The solid center, several thousand degrees Fahrenheit, heats this area. When the liquid is heated, it rises, cools, and then sinks down to be heated again. All of this churning causes an electric current and an electromagnetic field along with it. The magnetic shield around the Earth pushes cosmic radiation away from the planet’s middle and out towards the poles. Some birds, turtles, and bees use the same magnetic field to find their way when migrating.
An electric motor uses an electric current to create a magnetic field. The magnetic fields are lined up to push away or repel each other. The repelling causes a push against the rotor and makes it turn. If the rotor is broken and can not turn, heat will build up, and there may be a fire.
The information on your computer is saved on magnetic disks. Both the hard drive, made of steel, and the floppy disks, made with thin plastic covered with iron filings, can be easily magnetized. Computers then write a pattern of magnetized and non-magnetized areas onto the surface to hold your data. The problem with this storage is that another magnet can erase the information. CD-ROMS do not use electromagnetism for storage. They make microscopic indentations called pits and flat surfaces called lands to store information.
If you would like to learn more about magnets and perhaps try some experiments, read on for good source materials. Central Rappahannock Regional Library patrons may reserve our books by clicking on the title and going to our catalog to request the title.
In the Library:
Batteries, Bulbs, and Wires by David Glover.
Activities and projects introduce how electricity and magnets work at home and in the everyday world.
Electricity and Magnets by Barbara Taylor.
Tells how electrical energy is created with magnets to help power the things in your kitchen.
Experiments with Magnets by Helen J. Challand.
These experiments introduce magnets and magnetism and demonstrate the magnetic field and the properties, strength, and uses of magnets.
Janice VanCleave's Magnets: Mind-boggling Experiments You Can Turn into Science Fair Projects.
Learn how a compass works, what's a magnetic field, how to use a magnet to make electricity, and more! Twenty experiments to use as is and lots of suggestions for designing your own. For ages 8 to 12.
The Magnet Book by Shar Levine and Leslie Johnstone.
Thirty simple experiments explore magnetism and electricity.
Magnet Science by Glen Vecchione.
Explains magnetism and electromagnetism and has 26 experiments that range from the simple to the more complex. Also teaches how to do science "magic tricks" that are based on the principles of magnetism.
Magnetism by John Farndon.
Experiments relate to natural magnets, electricity and magnetism, magnetic fields, using a compass, and magnetic levitation.
Magnets: Pulling Together, Pushing Apart by Natalie M. Rosinsky.
A book for young children (grades 2 to 3) on the basic principles of magnetism. Includes simple experiments.
Play & Learn with Magnets by Gayle Bittinger.
Designed for preschoolers, this book finds ways to work basic magnet science into lots of activities: learning games, language, art, science, as well as music and movement.
Playing with Magnets by Gary Gibson.
A fun book of facts and experiments. Some can be done alone; some require an adult's supervision. For grades 1 to 3.
What Makes a Magnet? by Franklyn M. Branley.
For students in early grades who are just getting interested in science. The author explains how magnets work and gives directions for making a magnet and a compass.
On the Web
Magnet Man: Cool Experiments with Magnets
"This web site is devoted to magnetism and the cool experiments you can do with permanent magnets and electro-magnets. Some of the experiments are very basic - things you've done since second grade. Others are unique; perhaps you hadn't thought of doing some of these before, or had difficulty in trying to set them up. Lists of the materials needed for the demonstrations, directions on how to assemble them, instructions on how to show them, and notes on how they work are all here for you."
The Great Magnet: The Earth
An introduction to the history of magnetic science for older students. Includes a teachers' introduction. From the NASA site.
Magnets and Electricity
Uses simple words and pictures to show how magnets can be used to create electricity.
Making a Compass
This simple experiment requires a sewing needle (careful!), small bar magnet or refrigerator magnet, a small piece of cork, and a cup of water. Easy and interesting.
The New Book of Popular Science: Magnetism
You'll need your CRRL library card to access this article. The series is very popular, and most libraries also own the print version.
"Rover Reveals Magnetic Mars"
In August of 2004, NASA found highly magnetic rocks on the surface of Mars as well as magnetic dust everywhere which may answer questions about the planet's development and help with future long term missions. Lots of scientific detail in this short article.
World Almanac for Kids: Terrestrial Magnetism
A quick essay that touches on magnetic poles, dynamo theory, field intensity, paleomagnetism, and magnetic reversals.