Think for a moment about a small magnet holding pictures on a refrigerator door and an electronic appliance, such as a blender. Even though they seem very different from each other, magnets and electricity actually have a lot in common and sometimes even work together!
Have you ever noticed how a magnet can pull other magnetic objects, such as paperclips, toward itself? Can you feel a magnet pulling back when you pull it off of the fridge? Using iron filings, a strong magnet and a plastic bag, you can make that pulling force, called a magnetic field, visible.
To make it easier, you can use this magnetic field demonstrator instead of the plastic bag and loose iron filings.
Ask an adult to help you cut a sheet of paper so it will fit inside of the plastic bag.
Safety note: Because iron filings are very tiny pieces of metal, it is important to keep them away from contact with skin, eyes, mouth, and nose. They are dangerous if inhaled or swallowed. Please closely supervise children while experimenting with iron filings. After the experiment, we recommend deposing of the bag and filings inside of it.
The invisible area around a magnet that attracts other objects is called a magnetic field. Magnetic objects (such as paperclips) will get pulled toward the magnet if they are placed in this field. Because iron filings are tiny and each one is highly attracted to magnets (in other words, they are magnetic), they quickly "jump" into position in the pattern of the magnet's magnetic field. Anything that is outside of the magnetic field isn't affected by the magnet. Anything that is not magnetic, such as the paper and the plastic bag, is not affected either. Did you notice how the filings clustered together more at the magnet's ends? A magnetic field is strongest at the magnet's poles (the ends of a bar magnet). Each pole of a bar magnet has a different charge. You can see this by the different colors and the markings on the end: "S" for south and "N" for north. In magnets, opposite charges are attracted to each other while charges that are the same repel or push away from each other. You can test this by holding the ends of two bar magnets together - when you hold the ends marked "N" (the magnets' north poles) toward each other, you should be able to feel the magnets pushing away from each other. Flip one magnet over so that its south pole (marked "S") is toward the other magnet's north pole and notice how the magnets pull toward each other.
Did you know that the earth also has a magnetic field? In fact, Earth's magnetic field is quite large. Scientists think it is caused by Earth's core, which is made of molten (very hot, melted) iron, the same element you used to see the field lines of the magnet in the project above. Earth's magnetic field is important because it blocks wind caused by the sun and harmful radiation from space from reaching us on Earth.
What Is a Magnet?
A magnet is a solid object, usually a rock or piece of metal, that can push or pull objects made of iron. Go on a magnet hunt around your house to find out what types of objects are magnetic. Look around and make of a list of objects you see that you think will be attracted to a magnet and another list of objects you think won't be attracted. Test each object you wrote down by holding them close to a magnet, such as a horseshoe or bar magnet. (Note: Never use magnets on or near computers, cassette tapes, discs, or other electronic devices because it could damage the magnets inside of them!) Mark the items on your lists that stick to the magnet. Compare your results (the items that were and weren't magnetic) with your predictions (the lists you made at the beginning).
Did you learn anything from the results of your experimenting that proved some of your predictions to be false? Can you make a conclusion about magnets from your results? What were the objects that are attracted to your magnet made of? Most magnetic objects contain metal, but not all metal objects are attracted to magnets! Why? Metals such as iron, nickel, and cobalt are magnetic. Steel is also magnetic, because it contains iron. Metals including aluminum, silver, and brass are not magnetic. Plastic, cloth, and other materials are not magnetic. Where some of your predictions correct? You just used the Scientific Method to learn about magnets!
Magnets have two ends where the magnetic pull is strongest, a north pole and a south pole. The poles are named that way because if a magnet is floating in water, it will automatically align so that the magnet's north pole will point toward the earth's north and the south pole will point to the earth's south! A compass works to effectively tell you which direction you are going because it uses a magnetic needle which will always align its north pole with the direction north.
Magnets are fun to play with and they work great for sticking pictures on your fridge, but did you know that without magnets, you wouldn't have a working blender, fan, or vacuum cleaner? Many common household items contain electromagnets. An electromagnet is only magnetic when it has electricity flowing through it. Electromagnets are different from regular permanent magnets and since they aren't magnetic all of the time, they are called temporary magnets.
Electronic devices such as refrigerators, washing machines, lamps, telephones, TV's, stereos, and many other electronic appliances use electromagnets to help them work a certain way. For example, a blender has an electromagnet inside it with a permanent magnet surrounding the electromagnet. When you plug the blender into an electrical outlet and turn it on, the electricity flows through the cord, inside the blender base, and to the electromagnet. When the electromagnet comes in contact with electricity, it becomes magnetic, which makes it react with the permanent magnet that surrounds it. The electromagnet ends up spinning and turning the blender's blades along with it!