Making a compass to find magnetic north or south (depending on where you live) can be fun and educational for your kids. It’s great for girl scouts, cub scouts, or y-princess or guides, and really gets them thinking about the different items that can be used to make a compass.
- Sewing needle ~1 inch long.
- Small bar magnet (a refrigerator magnet may work)
- A small piece of cork, or anything else that will float on water (almost)
- A small glass or cup of water to float the cork and needle.
1. Your home-made compass will work better if you first run a magnet over the needle 20-50, in the same direction. Whichever direction you go with the magnet is the end that will determine direction (point towards the north).
This action ‘magnetizes’ it the needle. If your lost in the forest, you can use silk clothing in the same manner as the magnet, but run it over the needle 50-100 times.
2. Now you need something that will float on water, and can be turned (while floating on water) by a magnetized needle. As part of a craft project, you ask your kids to think about things that can float on water (a leaf, a small sliver of ivory soap, a blade of grass, a cork, a piece of styrofoam…).
For this example, you can use the whole cork from a wine bottle or cut off a small cylinder from one end of the cork. Rest the needle on top of the cut-off disc of cork; or you can stick a needle into the full cork. You may need to adjust it some as you try to get it to float flat on water (be careful not to stick yourself). I ended up using a leaf, which worked amazingly well (and is more readily available if you need this in a forest). I read somewhere that the oil from your face rubbed on a needle will help it float; but I could never get this to work.
3. Float the cork (or leaf, soap, etc.) with the needle in a cup of water or a pie tin (about an inch deep) so the floating needle lies roughly parallel to the surface of the water. You’ll have to keep it from the side of the dish so it has freedom to rotate.
The needle should come to point towards the nearest magnetic pole – north or south as the case may be.
4. You can have the kids play with a magnet around your homemade compass to see what kind of effect it has.
No one knows for sure, but there is a theory that the Earth’s core consists largely of molten iron. And at the very core, the pressure is so great that this super hot iron crystallizes into a solid. Convection caused by heat radiating from the core, along with the rotation of the Earth, causes the liquid iron to move in a rotational pattern. It is believed that these rotational forces in the liquid iron layer lead to weak magnetic forces around the axis of spin.