Point me in the right direction, please.
Magnets and compasses.
Background
For centuries sailors used compasses, which are simply magnets, to show them where they were going. This experiment will show you how to make your own compass using a sewing needle.
Let's do science...
The Experiment
If you take
bar magnets
and hang each of them using a piece of string so that they are horizontal to the ground, they will always swing around so that they are lined up along the north-south line of the earth. You will have a bunch of basic compasses.
In this experiment, you don't need a whole bunch of compasses but you are going to use this bit of information to make a one brilliant compass...
The Aim
To make a compass by magnetizing a simple sewing needle.
Equipment Needed
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 (do not take it out of your dad's best bottle of vintage wine!)
Scissors, pencil, ruler, marker or pen, wood glue and a compass – not like the one we are making but the thing you use to draw circles with – or something round, about 10cm in diameter.
Something solid to balance the compass on, like a piece of off-cut wood.
A bar magnet.
Method
Using the necessary stationary, cut out a circle from the cardboard, about 10cm across.
Now cut a circle out the center of the circle 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 – why do you need to do this (Hint: it has something to do with attraction).
Rub the bar magnet down the other needle about 40-50 times. Always start at the same end and always rub down the needle in one direction only.
Push the 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.
Results
Once the compass has been set up, as long as the compass face is placed in the right direction, the compass will always swing so that the needle faces north.
The Conclusion
The needle, and therefore the compass face that you made, lines up with the north-south line of the earth's
magnetic field
and so will always point north.
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