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How to determine the polarity of
an unmarked magnet

Shop for Magnets
Unmarked cylinder bar magnet Many magnets available for purchase do not have their north and south poles labelled, which can be a problem, particularly when teaching children the positions of the north and south magnetic poles.

There are a number of methods you can use to identify the polarity of unmarked magnets:

A piece of string

An unmarked bar magnet in a paper sling with a piece of string holding it up The traditional method of discovering the polarity of an unmarked magnet involves attaching the magnet to a piece of string with the help of a paper sling. You will also need a compass for this task.
Magnet on a string turning towards the magnetic north and south poles If you hold the end of the string and allow the magnet to move freely, it will align itself with the north and south magnetic poles, which can be identified by a compass.

Using another magnet

Marked and unmarked bar magnets Another way of testing the polarity of an unmarked magnet is to use an already marked magnet to highlight the north and south poles.
South pole of marked magnet being attracted to the north pole of an unmarked magnet The marked magnet attracts itself to the opposite pole of the unmarked magnet. For example, the marked magnet’s south pole will attach itself to the north pole of the unmarked magnet.

Compass

Cylinder bar magnet next to a compass pointing north with a labelled north and south pole The use of a compass can also aid in the identification of the north and south pole of a magnet. When you place a compass next to a magnet, the north pole of the magnet will follow the line of the north pole of the compass.