Compass making with your child is a wonderful way for you to teach him or her about Earth and its magnetic pole and geographical poles. It's also a great introduction to one of these devices that shaped the exploration of the world as we know it today. What a simple, yet remarkable device.
Why not get started by visiting your local library with your children? Check out some books on the Earth and on magnets and magnetism. Even if the book is above the reading level of your child, you can sit and look through the books together and gather ideas and information from the pictures, photos, diagram and maps. You can scan through the written information and chose some excerpts to read and share with your child. What you want to do is simply to offer them a brief explanation of the magnetic poles and the Earth's north and south poles; this will provide a background to give your child a little insight into how and why a compass works.
When you make your own compass, collect these few items before you begin. You will need a bar magnet (it will have North and South poles labeled on it), a 6-inch piece of thread, a sewing needle, a pin, some cellophane tape, an empty glass jar with a cover (a pickle jar works well), and a compass (to verify your homemade compass).
Start by tying one end of the thread around the center of the magnet so that the magnet balances horizontally when you hold it up by the thread. When the magnet stops swaying see which way the north pole on your bar magnet is pointing. Now compare this with the compass and the needle that is pointing in that. Line them up, both the bar magnet and the compass.
Do not let the magnet get too close to the compass because the magnet can attract the compass needle and then weaken its effectiveness.
Next you are going to rub the needle lengthwise along one of the poles of the magnet. Each rubbing stroke must be in the same direction - back and forth will not work. When you notice that the needle is magnetized enough to attract the pin, tie the thread around the middle of the needle so that it balances. Get the jar cover and tape the other end of the thread to the center of the jar lid. Gently lower the needle into the middle of the jar so that it hangs freely when you tighten the cover. Compare the way the sewing needle and the needle of the compass are pointing. You should see that the sewing needle has now become a compass needle because it is facing north like your other compass.
All of this happens because the Earth itself is a tremendous magnet. Scientists feel that the magnetic poles of the Earth are huge deposits of magnetite. The northern magnetic pole is about 1400 miles away from the geographic North Pole and the same holds true for the South Pole. The magnetic poles of the Earth change their position slightly from time to time. Magnets are attracted to the magnetic poles of the Earth. This is why the poles of magnets are called north-seeking, and why magnets can serve us as compasses.
Geographic and magnetic poles are not the same. Mariners and other people who need accurate information from their compasses correct their compass reading and positions with a chart which compensates for the slight errors that a compass may have at various locations. Just think about the sailors who navigate around the world. The difference between the magnetic and the geographic poles is called the angle of declination. A magnet will only point to true north when you are in those places that are in a straight line with the magnetic and geographic poles. This is just a bit of back ground information that you may be able to share and use with your children as you make your own compass and learn more about magnets. I'm sure the books from the library that you shared with your children will explain even more about the poles and magnetic fields.
Just about everyone remembers the old "Mr. Potatohead" set where you used a real potato and then dressed it up like a person, with accessories included in the kit. Kids had so much fun with the set that millions were sold.