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A "horseshoe magnet" made of Alnico 5, about 1 inch high.The metal bar (bottom) is a keeper. A magnet keeper, also known historically as an armature, is a bar made from magnetically soft iron or steel, which is placed across the poles of a permanent magnet to help preserve the strength of the magnet by completing the magnetic circuit; it is important for magnets that have low magnetic ...
Neodymium magnets are graded according to their maximum energy product, which relates to the magnetic flux output per unit volume. Higher values indicate stronger magnets. For sintered NdFeB magnets, there is a widely recognized international classification. Their values range from N28 up to N55 with a theoretical maximum at N64.
Alnico alloys can be magnetised to produce strong magnetic fields and have a high coercivity (resistance to demagnetization), thus making strong permanent magnets. Of the more commonly available magnets, only rare-earth magnets such as neodymium and samarium-cobalt are stronger.
The magnetic pole model assumes that the magnetic forces between magnets are due to magnetic charges near the poles. This model works even close to the magnet when the magnetic field becomes more complicated, and more dependent on the detailed shape and magnetization of the magnet than just the magnetic dipole contribution.
For a bar magnet, the direction of the magnetic moment points from the magnet's south pole to its north pole, [15] and the magnitude relates to how strong and how far apart these poles are. In SI units, the magnetic moment is specified in terms of A·m 2 (amperes times meters squared).
The magnet is inside the doughnut-shaped housing and can create a 3-tesla field inside the central hole. Superconducting magnets have a number of advantages over resistive electromagnets. They can generate much stronger magnetic fields than ferromagnetic-core electromagnets, which are limited to fields of around 2 T. The field is generally more ...
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Flux distribution for a flat refrigerator magnet Schematic diagram of a free-electron laser. Scaling up this design and adding a top sheet gives a wiggler magnet, used in synchrotrons and free-electron lasers. Wiggler magnets wiggle, or oscillate, an electron beam perpendicular to the magnetic field.