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.

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.

This week's experiment is an important part of my work. When demonstrating static electricity in my science shows, I always keep the hair drier nearby and I pay close attention to the weather forecast. To see how the weather and a hair drier fit in with static electricity, you will need:

- a hair drier
- several balloons
- small pieces of paper
- your hair (or a piece of cloth if you are "hair challenged" like me)
- a wet cloth or paper towel

First, blow up a balloon and tie it off. Small, cheap balloon work the best, but any sort should do the job. Then, tear some tiny bits of paper and place them on a flat surface. The pieces should be smaller than your fingernail. Rub the balloon briskly on your hair or a piece of cloth and then bring it near the pieces of paper. If you generated enough static electricity, then some of the pieces of paper should jump up to the balloon. If the paper did not jump to the balloon, then turn on the hair drier and use it to dry your hair and the balloon. Be careful not to get the balloon hot enough for it to pop. Once the balloon is dry, try it again. This time, the paper should jump very well for you.

Next, take the wet cloth and rub it gently over the surface of the entire surface of balloon. You want the balloon to be damp. Then rub the wet cloth lightly over your hair, to make it damp as well. Try rubbing the balloon on your hair again and bring it near the bits of paper. This time, you will get very little reaction, if any at all. Once again, dry the balloon and your hair with the hair drier and the paper will once again jump up to the balloon.

Why would water cause this? When you rub the balloon against your hair, you are transferring electrons (tiny, negatively charged pieces of atoms) from your hair to the balloon. Because electricity does not flow easily over rubber, the electrons are trapped there, building up a strong, negative static charge. It is this charge that attracts the bits of paper.

Rubbing the damp balloon against your wet hair still moved electrons from your hair to the balloon, but the water formed a conducting pathway. Instead of remaining trapped on the balloon, the electrons flowed across its surface to your skin and then to the ground. You never built up enough of a static charge to attract the paper bits. When you used the hair drier to dry the balloon and your hair, you removed this pathway, and once again the static charge could build up.

As the weather gets colder, the air is usually drier. That is why you get a lot more static shocks in the winter than in the summer. That is also why many science teachers save their unit on electricity until the coldest month. It makes the experiments much easier to do successfully.

This week's experiment comes from a question sent to me by 10 year old Will Boyd. His question was, "If I were standing directly on the South Pole and I was holding a compass, where would the needle be pointing?"

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This week's experiment is one that I played with while waiting for one of my programs to start. I started with one balloon, and then added another. As I tried different things, I began to have fun with the charged balloons. To try it yourself, you will need:

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Open any book or web page that talks about magnets, and you will probably see a drawing that shows magnetic lines of force that extend from one end of the magnet to the other.

Are there really lines of magnetic force as they show in the drawings? Well, lets find out. To try this, you will need:

- a file
- iron nails
- a small, plastic bottle cap
- clear, dish washing soap
- a strong magnet
- metal paper clips

If you tried the experiment from the Science of Credit Cards video, don't throw away the iron filings. If you did not, then you can use the file and iron nails to make about 1/4 teaspoon of iron filings.

Fill the plastic bottle cap about 3/4 with the dish washing soap.

Then stir the iron filings into the soap, until they are evenly distributed.

Place the bottle cap on top of a strong magnet. Watch the iron filings carefully as you put the magnet in place. You should notice that the filings are attracted to the magnet.

Looking closer, the magnetic filings stick together, forming lines that look very much like the drawing in the book. So there really are lines of magnetic force, right? No.

Wait a minute! What do you mean by "No"? I can see the lines, right there in front of me!

Well, there are lines of iron filings, but there are no lines of magnetic force. The magnetic field that extends around the magnet does connect one end to the other, but it is spread evenly, not in specific lines of force. Then why do the filings line up like that? To find out, lets look at some paper clips.

Pour a pile of paper clips on the table, and put the magnet into the pile. When you lift the magnet, the paper clips stick together, forming magnetic chains.

Each of the paper clips in the chain now has a north and south magnetic pole. In the photo, the paper clips are sticking to the north pole of the magnet, so on the first paper clip, the end that is touching the magnet will be a south magnetic pole. The other end will become a north magnetic pole, attracting the next paper clip in the chain. That paper clip will also develop north and south magnetic poles, and will attract the next paper clip in the chain.

The same thing happens to the iron filings. They attract each other, end to end, to form chains, just as the paper clips did. That is what forms the lines you see, not invisible lines of magnetic force. How do we know?

Remove the magnet, and stir the soap again. Put the magnet back, and you will see the lines form again, but if you look closely, you will notice that they are not in exactly the same place. If there really were actual lines of force, the filings would line up in the same place each time. Since the magnetic field surrounds the magnet evenly, instead of in lines, the locations of the chains of iron filings are random each time. You always get the chains, but they are always in different places.

The lines in the drawings work well for explaining magnetic fields, and the chains of iron filings reinforce that idea, but when you observe carefully, there are no magnetic lines of force.

Why does putting a plastic bag over a credit card make it scan better?

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Did you know that your television can show you how much smoke, dust and other pollution you have in the air of your home?

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This project has science fair potential.

Electrostatic fields can do some very interesting things. This is a simple trick that you can do almost anywhere, as long as you carry a balloon in your pocket.

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Make a stream of water move without touching it.

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Producing Static Charges

What is responsible for the sparks you get when you scuff your feet on the carpet?

An introduction to induction.

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Construct a simple device for detecting static charges.

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In the Sorting Salt and Pepper video ( http://thehappyscientist.com/science-video/sorting-salt-and-pepper ) we saw that we could mix salt and pepper into a pile and then separate them easily by using the static charge on a balloon. I challenged you to think of other ways to separate them, and you sent in lots of great ideas. Lets take a look at some of them.

We start with that same pile of mixed salt and pepper. How are we going to sort them out? Well, lets start by thinking about how salt and pepper are different.

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