This Week's Experiment - #311 Rubber Magnets
This week's experiment is one that I stumbled upon while working on another
idea. That seems to happen to me frequently. I was planning to magnetize a
needle and as I was sorting through all the magnets on our refrigerator, I
got sidetracked into playing with the rubber magnets (which are really
plastic, not rubber). The more I played; the more interesting it got. To
explore, you will need:
two of the flexible magnets that are commonly used as souvenirs
First, stick one of the magnets to the refrigerator or some other magnetic
surface. If you use the side that normally sticks to the refrigerator, it sticks. We will call that the magnetic side. Now try sticking the other side
(we will call it the "other side") to the refrigerator. Did it stick? No.
Next, try sticking the two magnets to each other. The two magnetic sides
will stick to each other. The two other sides will not stick to each other.
If you try sticking the magnetic side of one magnet to the other side of
another, they will stick very weakly. What is going on?
Usually, one end of a magnet is the north pole and the other end is the
south. Bring two different ends together and they stick. Bring two ends
that are the same together and they push away from each other. Did it work
that way with the flexible magnets? No. Why not? How can you have a magnet
that only has one magnetic side?
If you have three flexible magnets, it can be even stranger. Stick the
magnetic side of two of the magnets to each other. No problem, right? Now,
since they stick to each other, they must be opposite poles, right? A north
pole sticks to a south pole and repels (pushes away) another north pole. If
one of your magnets is a north pole and the other is a south, then your third
magnet should stick to one and repel the other, right? Try it.
The third magnet stuck to BOTH of them. We have several one sided magnets
that stick to each other. How can that be?
Now for some answers. Stick the magnetic sides of two of the magnets
together. Now, slide one of the magnets sideways across the other. If it
slides smoothly, then try sliding it from top to bottom instead of side to
side. In one of the directions (either side to side or top to bottom), the
magnets will slide smoothly. In the other direction, it will feel as if it
is sliding across a series of bumps. It will slide and stick, slide and
stick. This is the clue that we needed.
Instead of thinking of the flexible magnet as a single magnet, think of it as
hundreds of tiny horseshoe magnets, all lined up in rows. Each tiny
horseshoe magnet has a north pole and a south pole. They are lined up to
form stripes of magnetism. The stripes alternate, north pole, south pole,
north pole, south pole, etc. That is why two magnetic sides stick to each
other. The north stripes stick to the south stripes on the other magnet.
The "other side" is like the back side of a horseshoe magnet. It does not
have much of a magnetic field, so it does not stick to the refrigerator. As
you slide one magnet across the other, the stripes alternately attract and
repel each other, so it jumps and sticks, jumps and sticks. Who would have
thought that there was so much fun science sticking to your refrigerator?
As always, have a fantastic week.
From Robert Krampf's Science Education Company
PO Box 60982
Jacksonville, FL 32236-0982
904-388-6381
krampf@aol.com
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