Experiment of the Week - #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
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 if 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?