The Suspended Needle

A suspended needle is one of the most commonly known ways to improvise a compass.

A magnetised needle (nail or wire, etc) can be suspended from a thread. Provided it is balanced and not influenced by the breeze, the needle will indicate magnetic North. Some further information (know the polarity of the needle, or see the general direction of the sun, for example) will be required to determine North from South.

To make a magnetised needle there are three basic options.

The first is that maybe you don't have to do anything at all. Most magnetic materials (iron or steel) will probably has some residual magnetism. It will probably be very weak, perhaps too weak, but it's still worth giving it a go if you don't have a way to magnetise it your self.

The second way to make a magnetised needle is to place one end of a magnet in contact with the end of the needle, and stroke it quickly to the other end of the needle. It may be worth repeating this a few times, but always stroke in the same direction with the same eng of the magnet in contact with the needle.

The third way to make a magnetised needle is to wrap the needle with turns of an insulated wire and pass a direct current through the wire. So to do this you will need not only a needle, but also some insulated electrical wire, and probably a battery. Be very careful if using a large lead acid battery like a car battery for this. Too much current through the wire could cause it to melt or even explode!

A similar arrangement can be effected by supporting the needle in a cork floating on water, or on a piece of paper supported by surface tension on water.

How accurate is this method? Well than depends on your local magnetic deviation (or declination) – that is, how close magnetic north is to true or grid north. The needle will indicate either magnetic north or south depending on which way it is magnetised.