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How to Demagnetize a Magnet (page 2)

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Author: Beth Touchette

Results

Your results will vary depending on the strength of the magnet you are creating magnets with, and how strong you make your nail magnets. Both of the hammered nails should have been noticeably less magnetic. The one you pointed east before hammering may have shown less magnetism than the one you pointed north. The nail you put in the oven should have lost some of its magnetism, while the one you put in the freezer will not have lost any strength at all.

Why?

Metals have lots of interesting properties! The reason the hammered nails showed less magnetism is because the hammering wrecked the orderly arrangement of atoms. The nail facing east may have been even more demagnetized than the one facing north because its atoms could not reorient themselves to the Earth’s magnetic poles. Remember—the earth itself is a giant magnet!

Molecular Alignment of Magnets

Heating the nail in the oven increased the kinetic energy of the nail’s iron atoms. That means the atoms were free to move around more, resulting in a messy arrangement after heating. Remember—iron atoms should all be facing the same direction to create a magnetic field. If a metal is heated to a high enough temperature, it reaches its Curie point, at which it loses all of its magnetism.  On the other hand, putting the nail in the freezer decreases the kinetic energy of its atoms, making sure the atoms stay put and the nail retains its magnetism.

Going Further

Think of some other ways to demagnetize a nail. Maybe you could drop a magnetized nail several times (as refrigerator magnets sometimes do).  Perhaps you could place a nail in boiling water or let it rust a bit. Have fun, but be careful!

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