Magnets are materials that attract pieces of iron or steel. In ancient times, people first discovered magnetism when they found some naturally magnetic pieces of rock in the earth. They called these rocks lodestone. Loadstones have a lot of iron in them, but we now know that other materials can be magnetized as well. Nickel, cobalt, certain types of ceramics and certain blends of metals can also make good magnets.
If you could look at a magnet at the atomic level, you would notice that the magnet was divided into a number of smaller regions called domains. All of the atoms in a domain point in the same direction and, since each atom acts like a little magnet , all of their little magnetic fields add together to make a larger, stronger field. A magnet can be weakened if some of its atoms are thrown out of alignment. Hitting or heating a magnet is usually enough to scramble some of its atoms.
Magnets have north and south poles. The north pole of one magnet will repel, or push away, the north pole of another magnet, and the south pole of one magnet will repel the south pole of another magnet. But, if you put the north pole of one magnet near the south pole of another magnet, you'll feel an attractive force. You may have heard the saying "opposites attract ." This is just one of the rules of nature that scientists have discovered.
Everyone knows that magnets stick to refrigerators, but did you know that magnets are used in all sorts of things? Most of the magnets we are used to seeing are made from metals rich in iron . The kind we use to hold our school work to the refrigerator are called permanent magnets. They are magnets today and they'll be magnets tomorrow. They just hang there and continue to be magnets without us doing anything to them. Can you think of anywhere else you might find permanent magnets in your house? Did you know there's a magnet in the seal on the inside of your refrigerator door? You don't use that one to hold your school work, but it does hold the door closed when you're not looking for a snack or a cold drink. Some cabinet doors have magnetic latches too. Can you think of any other places where magnets have practical uses?
Permanent magnets are one kind of magnet, but there's another kind of magnet called an electromagnet. Electromagnets are made from metal and electricity! When the electricity is on, you have a magnet, but turn the power off, and you just have a hunk of metal and some wire. Unlike permanent magnets, the strength of an electromagnet is easy to change. One way to do this is to change the amount of current used. Another way is to change the amount of wire you have wrapped around the metal core. You see, when you wind wire in coils around a piece of metal that has a lot of iron in it, and then you run electricity through the wire, it creates a magnetic field. More coils of wire or more electric current creates a stronger magnetic field. This magnetic field causes the atoms in the core to align, giving the metal magnetic properties.
Electromagnets are used in many devices. Think of things that use power and have moving parts. Chances are, an electromagnet is causing the motion! Power windows in a car, automatic doors at the grocery store, and the little motor in a CD player that makes the CD spin so you can listen to your favorite music all contain electromagnets! Electromagnets really make our lives easier , and more fun, too!