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How to Demagnetize a Magnet

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Author: Beth Touchette

The first thing many kids do when they get home from school is open the refrigerator.  Is your refrigerator door covered with cards, photos and papers?  You probably already figured out that refrigerator magnets are attracted to the steel in the refrigerator door. Magnets are materials that attract iron (which is what steel is mostly made of), nickel and a couple other metals. A material is said to be magnetic if it acts like a magnet. The atoms within a magnet line up in groups with their north and south ends lined up with Earth’s magnetic pole. When many, many atoms are lined up in the same direction the material creates a magnetic field, which is the space around a magnet where the pull or push forces operate.

Now that we have discussed how your refrigerator magnets work, let’s investigate how to demagnetize a magnet. When we say that magnets can become demagnetized, we mean that they lose their ability to attract metals like iron.

Problem: How Can You Demagnetize a Magnet?

Materials

  • Stapler filled with staples
  • Grown-up
  • Strong magnet
  • 4  long iron nails
  • Ruler
  • Work table or other surface that you can hammer on
  • Magnetic compass (the kind you find direction with)
  • Masking or duct tape
  • Hammer
  • Freezer
  • Cookie sheet
  • Oven (you can’t use a microwave for this activity)
  • Hot mitt
  • Tongs

Procedure

  1. First, you need to make some magnet testers.  Ask your grown-up to open and close the stapler several times, without any paper, so several closed staples slide out.
  2. Next, you want to make some weak magnets out of the iron nails. Hold the nail’s head in one hand, covering at most the first 1 cm of the nail.
  3. Using your other hand, run the magnet down the nail to the tip.  Lift up, and repeat.
  4. Continue magnetizing the nail for three minutes.
  5. Test the strength of your newly created magnet.  You should be able to pick up at least three closed staples at the tip of the nail.  If you can’t, continue magnetizing your nail until you can.
  6. Using the other nails, create three more weak magnets the same way.  Use the staples to confirm that all your nails are about the same strength.
  7. Put one of your magnetized nails in the freezer for at least an hour. 
  8. Put another one of your magnetized nails in on a cookie sheet in a 350 degree oven for a half hour.  Why can’t you use a microwave to heat your nail?
  9. As you’re waiting for your nails to be heated and cooled, you can test the effect of striking one of your magnetized nails.
  10. Set your compass on the hammer safe surface and turn it so that the needle points north.
  11. Lay a magnetized nail adjacent to the compass. The point of the nail should face east.
  12. Remove the compass, and tape the nail to your surface.
  13. Ask a grown-up to hammer the nail on the table twenty times.
  14. Now, see how many staples the nail can pick up.
  15. This time, lay another magnetized nail so that the needle points north.
  16. Remove the compass, and tape down the nail.
  17. Ask a grown-up to hammer the nail on the table twenty times.
  18. See how many staples this second nail can pick up.
  19. Record your results in a data table.

Demagnetizer

Number of staples picked up

Newly magnetized nail - control

 

Hammer East/ West

 

Hammer North/ South

 

Hot Oven Nail

 

Frozen Nail

 

Other idea 1

 

Other  idea 2

 

  1. Asking your grown-up to use the hot mitt and tongs see how many staples the hot magnetized nail can pick up. 
  2. Remove the nail from the freezer, and immediately test how many staples it can pick up.
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