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Magnets & Magnetism
What is a Magnet?
That's a great question and one that you just might have to see for you to really understand. Be sure to do the science projects in this issue to learn how and why magnets work!
Project 1: What's the Attraction?
All magnets have the ability to attract other magnets or magnetic objects (such as iron and some other metal objects). But a magnet doesn't necessarily have to touch a magnetic object for the object to be attracted to it. Try this experiment to learn why.
What You Will Need:
What To Do:
All magnets have a magnetic field - an area around a magnet where its magnetism affects other objects. By measuring how far the magnet was from the paperclip when they become attached, you were finding the length of the magnetic field. Stronger magnets can generally attract magnetic materials from a farther distance than weaker magnets can. Based on that fact and the results you wrote in your notebook, which of your magnets was the strongest? Which one was weakest?
Project 2: Which Magnet Is the Strongest?
A good way to test how strong different magnets are is to see how many magnetic objects it can attract. Try this experiment with your magnets!
What You Will Need:
What To Do:
When a magnet touches another magnetic object (such as a paperclip), the object becomes a temporary magnet for as long as it is touching the real magnet! It can now be used to pick up more paperclips. Each additional paperclip also becomes a temporary magnet with a weaker magnetic force than the one before it. Some magnets may be able to hold a chain of five paperclips while another magnet may only be able to hold one or two paperclips. How many paperclips a magnet can hold is a good indication of its strength. If you have a strong enough magnet and lift up the paperclips long enough, you may find that some of the paperclips will keep the ability to act like magnets for a little while even when they are not touching the magnet. If this happens, you have just made a very strong temporary magnet.
Important Science Terms
Magnetic object - any object that can be attracted to a magnet. Paperclips, iron filings, keys, and bobby pins are all examples of magnetic objects.
Magnetic field - an invisible area around a magnet where its magnetic force affects other objects. The magnetic field is what actually pulls other magnetic objects towards a magnet.
Temporary magnet - a magnetic object that can become a magnet when it is touching a permanent magnet but loses its magnetic properties when it is no longer touching the permanent magnet.
Science Question of the Month
Question: "What causes the poles of a magnet to be opposites?"
Answer: All objects are made of tiny particles called atoms which have negatively charged electrons spinning around inside them. This spinning creates a small magnetic field. In most objects, these electrons are spinning in opposite directions, cancelling out any charge (or pull) that could be made by them. In magnets, however, these electrons spin together in the same direction, increasing their charge and their pull (magnetic field). This causes little regions, known as magnetic domains, where all the atoms in each region line up together so that they are all pointing in the same direction.A way to explain why the poles of a magnet are opposite is to think of these atoms as little arrows. In each magnetic domain, the atoms are lined up so that their "arrows" are all pointing in the same direction. In non-magnetic items, these arrows point in random directions, which cancels out their magnetic fields. In a magnet, the arrows can only point in one direction. When two magnets are placed close together with their arrows pointing towards each other (same poles facing each other), the arrows are not lining up together, so they try to get away or repel each other. But when the arrow tips of one magnet gets close to the opposite ends of the arrows of another magnet (opposite poles facing each other), the arrows are already pointing in the same direction so the magnets are attracted and automatically pull towards each other.
To see an illustration of this, go to http://science.howstuffworks.com/magnet1.htm.
The size of a magnet doesn't necessarily match its strength. The Earth has a magnetic field and acts like a big magnet, but it isn't very strong. In fact, a refrigerator magnet has a magnetic field that is about 20 times stronger than the magnetic field of the Earth.
A neutron star (what is left over after a star has collapsed) has the strongest magnetic field of any object in the Universe!
Special trains, called Maglev trains, use magnets to help them travel at very high speeds (up to 310 miles per hour!). The trains have huge magnets attached to their undersides that allow them to float along special tracks of metal coils.
What did one magnet say to the other magnet?
What object can pull something towards it, without even touching it?
Way Cool Websites
Rubbing a nail over a magnet several times in the same direction can make the nail magnetic. Make a virtual magnet to see how this happens.
Do an activity to learn more about magnets, then test your knowledge about magnets with a quiz!
What Is a Magnet?
A magnet is a solid object, usually a rock or piece of metal, that has the ability to attract certain materials. To help discover what is and what is not attracted to magnets, go on a magnet hunt. Look around the room and help your child make a list of objects he or she thinks will be attracted to the magnet as well as a list of objects that will not be attracted. After making your lists, test each of the objects. (Don't use magnets on computers, cassette tapes, discs, and other electronic devices - it could damage the magnets inside of them!) Compare your results with what you predicted would be attracted. Were you correct on all your predictions? Were you wrong on any?
Discuss why items did or did not stick when you originally thought the opposite would be true. For instance, the object is made out of plastic but coated with shiny paint to make it look metallic; not all metals are attracted to magnets; or maybe just parts of an object were attracted to the magnet. What does this tell us about magnetic attraction? (That an object must be made out of metal to be attracted, but not all metals are attracted.) Metals such as iron, nickel, and cobalt are attracted to magnets. Steel has iron in it, so it is also attracted to magnets.
Alternatively, you can use this coloring page as part of a magnet hunt. Go around the house and find things that are magnetic. Circle the items on the coloring sheet that are attracted to the magnet and draw in any other items you found that are also magnetic.
As mentioned before, many common household items have magnets in them and are part of what makes these items work. Electronic devices such as refrigerators, washing machines, lamps, telephones, TVs, and stereos all have magnets in them.
Attraction and Repulsion
All magnets have two ends where the pull is strongest - a north pole and a south pole. The poles are named this way because if a magnet is floating in water or is suspended by a string tied around its middle, it will align itself in a north-south direction, consistent with the magnetic field of the Earth.
To best show how the poles of magnets react with each other, get two bar magnets with the north poles and south poles labeled. Holding firmly onto the magnets, have your child try to push their hands and the ends of the magnets together so that the north poles of both magnets meet. What happens? Now flip one of the magnets around and try pushing the ends together so that a north pole of one magnet meets with the south pole of the other magnet. What happened this time? Finally, flip the other magnet so that the south poles are facing each other and try to push them together. What happened?
Children should find that when a north pole was facing a south pole, they felt a force pulling the magnets together. But when the north poles were facing each other or the south poles were facing each other, they should have felt a force pushing them apart. Help children understand that opposite poles attract (pull together) while similar poles repel (push apart).
The invisible area around a magnet which attracts another object is called a magnetic field. Magnetic objects (such as paperclips) will get pulled towards the magnet if they are placed in this field. You can see the magnetic field of a magnet using iron metal filings in a Ziploc bag or iron filings in a sealed case. (We highly recommend putting loose filings in a sealed bag to avoid a mess.) Lay a bar magnet on a table. Gently shake the bag or case to evenly distribute the iron filings and lay it on top of the magnet. (You may also want to try placing the magnet on top of the Ziploc bag.) Observe the pattern of the iron filings. The magnetic field is strongest at the poles. You can see this because the iron filings cluster at these points.
Now place two bar magnets on the table with similar poles facing each other. Place them as close together as possible without them moving away from each other. Place the iron filings on top of the magnets. Observe the pattern of the iron filings. Now flip one magnet around so that opposite poles are facing each other and get them as close as possible without them moving together. Place the iron filings on top and again observe the pattern made.
In each of these experiments, the iron filings allow us to visibly see how the magnetic field is shaped and how multiple magnetic fields can interact with each other. Extend this by trying different magnet shapes (ring magnet, horseshoe magnet, etc.) to see what their magnetic fields look like. Also try it with multiple magnets close together to see how their magnetic fields interact with each other.
Adult supervision should always be provided when children are playing with magnets.