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 Permanent magnets and dipoles
All magnets appear to have at least one north pole (reckoned positive) and at least one south pole (reckoned negative), and the net pole strength of every magnet is zero. Despite their apparent reality, as suggested by the image at the top of the page, where iron filings concentrate in regions of large magnetic field, poles are not physical objects on or in the magnet. They are, rather, a useful concept for describing magnets. Rather than poles being the fundamental unit, it is the magnetic dipole that is the fundamental unit. A magnetic dipole can be thought of as a combination of a positive and a negative pole that are microscopically close to one another and inseparable. This is not a bad description of the magnetic dipole of an electron in a magnetic material.
By aligning a large number of these dipoles (say a million), and placing them head-to-tail in a line, we find that there is a north pole at one end and a south pole at the other, but all the intermediate north and south poles cancel out one another. The net effect is a very long dipole that appears to have poles only at its ends. Theories have been developed involving the possibility of north and south magnetic monopoles, but no magnetic monopole has yet been found.
Resources- Magnets
- Rare-earth magnets
 Rare-Earth Magnets
- Neodymium, Iron, and Boron — Nd2Fe14B NdFeB Magnets
- Samarium-cobalt Magnets SmCo Magnets
- Aluminium, Nickel and Cobalt AlNiCo Magnets
- Permanent Magnets and Dipoles Permanent Magnets
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