Experiments in Which Objects Are Attracted to a Magnet
The force of magnetism underlies many of the important devices we rely on in our daily lives, including machines like motors and generators. Magnets are popular both as toys and in classroom demos -- not only because they're fun, but also because simple experiments with magnets can help illustrate some of the basic principles of physics.
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Iron Filings
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Place a magnet beneath a sheet of paper and sprinkle iron filings on it; the filings will line up in a way that reflects the structure of the magnetic field. This common experiment helps students to understand magnetic field lines. Staples will work in place of iron filings if need be. Another way to visualize the field involves moving a small compass around in the vicinity of the magnet; the compass will always align itself with the magnetic field. Be careful when conducting this experiment, because the compass may be ruined if brought too close to the magnet for too long.
Rubbed and Unrubbed Nails
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Take a magnet and stroke an iron nail with the North pole end. Make sure that you stroke in one direction only. The iron nail will now act like a miniature magnet, so you can use it to attract other iron objects. The magnetic field of the nail will be fairly weak, but it should be sufficient to pick up small items like iron filings. Magnetizing a nail then striking it with a hammer, rubbing it in the other direction or placing it in a hot water bath are other experiments you can conduct to determine how permanent magnets become demagnetized.
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Magnets
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Another experiment involves placing a wire between the south pole of one magnet and the north pole of another, then running a current through the wire. The magnetic field will act on the wire once it is carrying current, causing it to deflect slightly. Also try hanging a magnet on a string from a nail, then place three other magnets below it on the table. Watch what happens as attraction and repulsion act on the magnet and cause it to swing.
Other Experiments
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Try suspending a bar magnet so that it hangs in the air and can rotate freely. Make sure it's suspended securely so it doesn't fall. At first the cord or string by which the magnet is suspended will twist and untwist, but eventually the magnet will orient itself so that it is aligned with Earth's magnetic field -- because Earth is essentially a magnet as well, and the two magnets interact with each other. You can also place two magnets at a distance from each other on a lab bench with the north pole of one oriented towards the south pole of the other. Try mounting the magnets on small carts or wheels so they can move more freely. They'll attract each other -- a demonstration that illustrates how potential energy is converted to kinetic energy. Also try placing an obstacle between the magnets, like a sheet of paper or a board of wood. Ask your students to predict whether the magnets will still attract each other.
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