Kids Zone stuff:

Voltage Game
Static Electricity Experiments
Build Your Own Compass
Guar Gum Slime
Optical Illusions

What is a compass? What is it made of? I mean, could you just write "NORTH" on a piece of wood and call it a compass? No, a compass is made when you have a magnet that is free to spin around, and free to point towards the earth’s north pole. If you’ve ever gone camping or hiking, you probably know how important a compass is. When you don’t know where you are, and there’s nothing familiar around to tell you which way to go, it’s always useful to have a compass to point you in the right direction, because the earth’s north pole always stays put. Also, compasses are cool, so let’s build our own!

Materials you'll need:

• Styrofoam cup
• Small bar magnet, with north and south ends, Magnet should be smaller than the base of the Styrofoam cup, too.
• Small, see-through container with watertight lid (like a small jar), but it must be bigger than the base of the Styrofoam cup.
• White PVA glue
• Waterproof marker (careful, it doesn’t wash off clothes easily)
• Scissors
• Water
  

What to do:
1) Cut the bottom off the Styrofoam cup, and try to leave it as flat as possible (no lip left sticking up). This is because if there is a lip sticking up, it will hold water in, making the Styrofoam bottom sink easier if water gets in it. Also, try not to cut too much off the sides (leave it as wide as possible) because the wider it is the, better it will float.

2) Glue the small bar magnet down flat onto the very middle of the Styrofoam circle you cut out. Try not to glue the magnet off to the side, or the Styrofoam circle will flip over in the water. Also, don’t use too much glue, because more glue means that the whole thing is heavier, making it more likely to sink.

3) Leave the glue to dry overnight.

4) Fill the jar (or whatever see-through, watertight container your using) halfway with water.

5) Place your Styrofoam circle with the magnet glued to it in the water, and make sure it floats. If the magnet doesn’t float, cut another bottom of a Styrofoam cup out and glue it underneath the first one. Again, don’t use too much glue, or it might be too heavy to float.

6) Now you need to calibrate the compass, which means, you need to label the north end of the compass, and there’s a few ways to do this. One way is to find out which way is north, then leave the floating magnet in the water, without anything metal or electrical near it, and whichever end of the magnet points north is the north end of the magnet. Another way is if you have another magnet that has its north and south ends already labeled, so you know that the north end of the floating magnet is whichever end is attracted to the south end of the labeled magnet (because opposite poles attract). Either way, once you know which end of your floating magnet is north, write a large “N” on that end of the magnet with the waterproof marker.

7) Now, place your floating magnet in the half full, watertight container you’re using, and put the lid on and close it tight. Make sure that the container does not leak, or else your new compass could make a mess. If it does leak, find another container to use, or seal it with some waterproof tape.

8) Now you have a compass that you can take with you when you go hiking, or camping, or whenever you want to know which way is north. Remember to change the water and clean out the inside of the compass every couple of months, or if you see it getting dirty inside. Also, even though this compass is designed to still work if it’s turned upside down or moved around, that doesn’t mean you shouldn’t be careful with it. If you shake it up too much, or toss it around, the container could break, or the magnet could fall off the Styrofoam, so be careful.

What's going on here?
If you’ve ever played around with magnets, you might know that every magnet has two ends (called poles), a north pole and a south pole. Even more important to know is how the poles interact with each other, which is given by the simple rule “Like poles repel, and opposite poles attract”. This means that if you have the north end of one magnet close to the south end of another magnet, they’ll try to move towards each other, because north and south are opposite so they attract each other. However, if you have two north poles near each other, or two south poles near each other, they will try to move as far apart as possible, because they are alike so they repel each other.

But how does this explain why a single magnet, all on it's own, will spin in a compass? Well, the earth has its own giant magnet deep in the center of the planet, and this magnet never changes. It might not be a very strong magnet, but as long as there aren’t any other magnets or metal objects near you, it can affect any magnet you have anywhere on the planet. As long as the magnet is free to move around, the north end of your magnet will point to the earth’s north pole. The magnet isn’t free to move around if you’re holding it in your hand, though, but if you can make it float on water then it’s free to spin. And when it's free to spin, it aligns with the earth's magnet, and then you know which way is north!

NOTE: Wait a minute, why does the north end of our compass point north? Don't north and north repel each other? Well, they do, but it turns out that what we call "North" is actually the south pole of earth's magnet! What happened was somebody messed up a long, long time ago and named the south end of earth's magnet "North", and the north end of earth's magnet "South", and then everyone just went along with it. Wow, talk about your big mistakes!