For centuries sailors knew how to use magnets in the form of compasses to show them where they were going. Compasses are fascinating instruments. In fact, when thinking about it, the concept of a magnetic field on the surface of the earth, which is what allows compasses to function, is in itself a fascinating phenomenon.
Although fascinating, a compass is very simple in the way that it works. A magnet, suspended and light enough to be influenced by the magnetic field in which it finds itself, will automatically line up with the north-south line of that magnetic field. If the only magnetic field in the magnet's sphere happens to be that of the earth's, you have a simple compass.
So if compasses are simple enough in design, how about making your own? Well, it just so happens that outlined below is a method to make a workable compass, using mostly materials found around the home. . .
What you going to need. . .
- 2 fairly large sewing needles (please be careful with them, these little things have been known to be quite sharp!).
- A piece of cardboard (at least 10cm x 10cm).
- A cork.
- Scissors, pencil, ruler, marker or pen, wood glue and a compass - not like the one you are making but the thing you use to draw circles - or something round, about 10cm in diameter.
- Something solid to balance the compass on, like a piece of off-cut wood.
- A bar magnet.
How to make the compass. . .
- Using the necessary stationary, cut out a circle from the cardboard, about 10cm across.
- Now cut a circle out the center of the circle of cardboard about 1 to 1,5cm across. The easiest way to do this is to fold the circle in half, find the midpoint using a ruler, draw a half circle around the midpoint, and then cut it out before unfolding it again.
- Use the pen and ruler to divide it into 4 quarters. At each end of the lines write the 4 main points of a compass, N, E, S, W (in a clockwise direction). This is your compass face.
- Cut a strip of cardboard about 7cm long and 1cm wide, and fold it in half.
- Stick a cork onto a solid foundation with wood glue.
- Push the one needle into the cork so that it is sticking up. Wrap some cellotape around it - this is to insulate it so that the magnetized needle doesn't stick to it.
- Magnetize the other needle by rubbing the bar magnet down the needle about 40-50 times. Always start at the same end and lift the magnet away from the needle to take it back and rub it again, always in the same direction.
- Push the magnetized needle through the folded, straight piece of cardboard at the “loose" ends so that you can open up the loose ends with the needle holding them open.
- Place the “compass face" onto the joined end of the straight cardboard, with the needle along the N-S line.
- Balance the compass on the needle sticking into the cork at the folded end of the straight piece of cardboard.
Once the compass has been set up, as long as the compass face is placed in the right direction and the needle remains magnetized, the compass will always swing to show the correct direction.
And, so, along with the sailors of old, you can, with your rustic compass, navigate your way home through the urban jungle safely to your home. With your newly acquired compass manufacturing skills, who needs a GPS?
By Neil Madgwick -
Passionate about science!