MadSci Network: Edible/Inedible Experiments Archive

Making a compass

Area of Science: Earth Sciences
Meant for at least Grade 4-6 (age 8-10).
This experiment is inedible.
An adult need not be present.

Make a simple compass to find magnetic north, or south, depending on where you live.

1. Sewing needle ~1 inch (3cm?) long.
2. Small bar magnet. Refrigerator magnets may work if you don't have a bar magnet.
3. A small piece of cork.
4. A small glass or cup of water to float the cork and needle.

Needles are sharp.. treat appropriately.

How to do the experiment:
1. Your compass will work better if you first run a magnet over the needle a few times, always in the same direction. This action 'magnetizes' is to some extent. Drive the needle through a piece of cork. Cork from wine bottles works well. Cut off a small circle from one end of the cork, and drive the needle through it, from one end of the circle to the other, instead of through the exact middle - be careful not to stick yourself!

2. Float the cork + needle in your cup of water so the floating needle lies roughly parallel to the surface of the water.

3. Place your 'compass' on a still surface and watch what happens. The needle should come to point towards the nearest magnetic pole - north or south as the case may be.

4. If you want to experiment further, try placing a magnet near your compass and watch what happens. How close/far does can the magnet be to cause any effects?

The earth produces a magnetic field. This field, although weak, is sufficient to align iron and other paramagnetic compounds such as your needle within it. By floating the needle on the cork, you let it rotate freely so it can orient itself within the earth's magnetic field, to point toward the north or south poles of the planet.

Useful References:

Further comments:
Try some of the files on this site discuss the nature of the earth's magnetic field and how it is produced.

Experiment submitted on Fri Apr 4 23:41:48 1997 by:
Name: J. Manns
Institution: U. Iowa
Position: undergrad

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