Activity: Make your own Compass

Talia about to float her magnetic needle

On SCOPE's Magnets episode, you saw Talia make a compass using a magnet and a needle. Here's how she did it. Watch the clip.

What you need

• A sewing needle
• A cork
• A magnet (with north and south marked)
• A bowl of water

What to do

1. First up you need turn the needle into a magnet. To do this, rub the needle on the south end of the magnet. You rub the needle in only one direction - from the head towards the point of the needle.
2. Repeat this 20 or 30 times.
3. This will make the point of your needle magnet North and the eye of the needle South.
4. Cut a thin round disk from a cork, and sit the needle on top.
5. Fill a bowl with water and float the cork and needle combo.
6. The needle should quickly line up with North and South (you can even mark them on the bowl)

What's happening?

The Earth is basically a giant magnet, and like all magnets it has a North and a South Pole. In this experiment you make a small free moving magnet that is attracted to and will line up with the Earths magnetic field. Most compasses you buy are floating needle magnets as well.

The needle is mostly composed of iron, and by stroking it in one direction with a magnet, you induce a magnetic field in the iron. It will remain a magnet for some time, although heat and shock (dropping it) will re-randomise the magnetic parts of the iron you lined up with the magnet.

It is slightly strange that the north end of a magnet or compass is attracted to the North pole of the Earth (because it two regular magnets, north and north repel, not attract). The main reason is that magnet poles were named after the Earths poles to which they were attracted. The Earth's Magnetic North pole is actually equivalent to a south pole on a regular magnet.

Weird huh?