Poles in a Circular Magnet

Curiously, always two!

If you just want to get a close approximation you can use an ordinary compass. If you need something more than that, you'll need a calibrated instrument to measure the magnetic field.

NOT True! Although many circular magnets do indeed have two poles, one on each end, it is quite possible to magnetize them with more, commonly around the periphery. Many stepper motors have a single magnet and use pole pieces to produce the multiple poles required, but some low-resolution stepper motors have a single magnet magnetized with 4, 6, 8, etc poles. The number of poles is determined by the structure of the magnetizing field(s). As posted in another response, cover the magnet with paper or put it in a plastic bag and sprinkle iron filings on it to see the fields and locate the poles.

You can test the magnet by using a sheet of paper and some steel filings. Cover the magnet with the paper and sprinkle on the filings. The filings will aline with the lines of magnetic flux, showing the flux path to the other pole.

The compass needle "South" end will point to the North pole of the magnet, when the two are placed close together.

Circular magnets have two poles, one on each end.

I just took a picture of a circular magnet with iron filings showing the 8 poles (This one is from the drive motor of a 5.25" floppy disk drive). Unfortunately, this forum does not seem to support pasting graphics, so I can't post it. I'll be glad to send a jpeg to anyone interested. Dick (dkwarner@mindspring.com)

Actually, magnets can be magnetized in a wide variety of configurations. A magnet such as the originator mentioned can be magnatized radially, axially or a combination of these depending on what is needed by the application. Are you trying to reverse engineer an existing product or what is it that you are attempting to do? There are several ways of measuring the field. A simple gauss meter will measure field strength, A polengiser will tell you which pole is in what orientation and a Helmholtz coil will give more advanced info.