# Why the poles parts of the magnet are stronger then the other parts of the magnet?

1. Sep 4, 2007

### stmartin

Are the force around the poles compressed, so it makes the poles of the magnet stronger than the other parts? Thanks.

2. Sep 4, 2007

### genneth

There is no "force" around a magnet. There is a field. The field affects things with magnetic charge -- in the case of magnetisms, magnetic dipoles. The field looks roughly like that pattern you get when you sprinkle iron filings about the magnet. The force exerted on a dipole due to a field is proportional to the strength of the dipole (obviously -- we actually define strength of dipoles this way) and the rate at which the field falls off. Note that all dipoles will experience a torque that tries to align them to the field (which is why the field is shown by iron filings -- they're miniature dipoles), but only a non-uniform field causes a linear force, displacing the dipoles. If you study the field lines about a bar magnet, you will notice that the field lines "come together" to end at the pole -- this signals the fact that the field is strongly varying there, because you go from very few lines crossing per area to many lines crossing per area. Thus a dipole placed there feels a much greater force.

3. Sep 4, 2007

### stmartin

Ok, thank you very much.