This week's experiment is a fun science puzzle involving magnets. To try
it, you will need:

- a strong magnet (available at most hardware stores)
- three paper clips

Straighten two of the paper clips, so that you have two long, fairly straight
pieces of wire. Get both as straight as you can. Place one aside. Hold
the other, and rub one end of the magnet along the paper clip, starting at
your finger, and moving to the other end. Move the magnet away from the metal
and repeat the process. Keep stroking the magnet along the paper clip, always
in the same direction, for about 40 strokes. By doing this, we are
magnetizing the paper clip.

Test the magnetized paper clip by bringing one end of it near the extra paper
clip, the one that you did not straighten. If your paper clip is magnetized
enough, it should attract the other clip. If not, try again with the
procedure above.

Once you have the paper clip magnetized, you are ready for the challenge.
Put both of the straightened paper clips together. Mix them until you are not
sure which is which. The challenge is to figure out which one is the magnet
and which is not, but you cannot use ANYTHING else to test with. No fair
using the third paper clip, iron filings, a compass, or anything else. You are
also not allowed to break the paper clips. The two straightened clips are
all you need to figure it out.

So, how do you find out which is which? If I told you, you would just say,
"Oh that makes sense." instead of really trying it. If you are really
patient, you could wait until next week for the answer, but I bet you have
enough scientific curiosity to actually get the materials and try it yourself.

Well, last time I left you with a challenge. If you have two metal rods (straightened paper clips) and one of them is magnetized, how to you find out which is which, without using anything else? To find out, you will need:

- steel wool
- a sheet of paper
- the two paper clips we used last time (or you can make two new ones)

I know that I said you could not use anything else. The steel wool is for later, to help explain what is happening. Pick up the two paper clips and bring the ends together. They should stick if they are still magnetized. OK, so which one is the magnet? To find out, we need to do something different. Bring the end of one paper clip near the middle of the other paper clip. Does it stick? If it does, then it is the magnetized clip. If it does not, then bring one end of the other paper clip to the middle of that one. The magnetized clip will stick to the middle of the nonmagnetized clip. The nonmagnetized clip will NOT stick to the middle of the magnetized one. Why?

Place the magnetized clip on a sheet of paper. Hold the steel wool over the clip, grab the two ends of the wad of steel wool and rub them against each other. Tiny bits of steel wool should fall onto the paper, and you should notice that they are sticking to the paper clip. Pay close attention to where on the paper clip they stick. The ends, right? That is where the magnetic pole is, and it is where the magnetic field is strongest. The middle of the paper clip has almost no magnetic field at all, so the steel wool does not stick there.

Now you know why the nonmagnetized clip would not stick to the middle of the magnetized clip. The magnetic field in the middle was not strong enough to attract it. On the other hand, the end of the magnetized clip will stick to any part of the nonmagnetized clip.

Not at all hard to figure out, once you know the science.