In an electromagnet the magnetic field is created through electric current in a wire-wound coil and strengthened by a soft-iron core. As soon as you turn off the power, the soft-iron core loses its magnetisation. A permanent magnet is made of ferromagnetic material, which is magnetised by a strong external magnetic field. The magnetically hard material that is used keeps part of its magnetisation after the external magnetic field is turned off.
The attraction between magnets is a little stronger than the repulsion. That is due to the alignment of the molecular magnets in the magnet. The attraction as well as the repulsion of magnets decrease significantly with increasing distance.
A magnet having a preferred direction of magnetic orientation, so that the magnetic characteristics are optimum in one preferred direction.
A magnet material whose magnetic properties are the same in any direction, and which can therefore be magnetized in any direction without loss of magnetic characteristics.
Remanence Br is a measurement for the magnetic induction or magnetic flux density that, after successful magnetisation, remains in the magnet. Simply said: the higher this value is, the "stronger" the magnet. T (Tesla) is used as the unit of measurement for magnetic induction and, respectively, magnetic flux density. The unit of measurement previously used was G (Gauss). 1 Tesla = 10 000 Gauss.
The maximum energy product is a measurement for the maximum amount of magnetic energy stored in a magnet. It is the maximally attainable product of flux density B and field strength H for a material. The unit of measurement is kJ/m³ (Kilojoule per cubic meter) or MGOe (Mega-Gauss-Oersted). Simply put, the maximum energy product is an indicator of magnet strength. You can either use a small magnet with a higher energy product or a large magnet with a lower energy product for the same application.
The temperature at which the parallel alignment of elementary magnetic moments completely disappears, and the material is no longer able to hold magnetization.
The second quadrant of the hysteresis loop, generally describing the behavior of magnetic characteristics in actual use. Also known as the B-H Curve.
The point at which the B-H curve ceases to be linear. All magnet materials, even if their second quadrant curves are straight line at room temperature, develop a knee at some temperature. Alnico 5 exhibits a knee at room temperature. If the operating point of a magnet falls below the knee, small changes in H produce large changes in B, and the magnet will not be able to recover its original flux output without re-magnetization.
Lines of magnetic flux per square centimeter, cgs unit of flux density, equivalent to lines per square inch in the English system, and Webers per square meter or Tesla in the SI system. Gaussmeter: An instrument that measures the instantaneous value of magnetic induction, B. Its principle of operation is usually based on one of the following: the Hall effect, nuclear magnetic resonance (NMR), or the rotating coil principle.
A cgs unit of measure used to describe magnetizing force. The English system equivalent is Ampere Turns per Inch, and the SI system's is Ampere Turns per Meter.
The direction in which an anisotropic magnet should be magnetized in order to achieve optimum magnetic properties. Also known as the "axis", "easy axis", or "angle of inclination".
This exists when the flux path external to a permanent magnet is confined within high permeability materials that compose the magnet circuit.
Circulating electrical currents that are induced in electrically conductive elements when exposed to changing magnetic fields, creating an opposing force to the magnetic flux. Eddy currents can be harnessed to perform useful work (such as damping of movement), or may be unwanted consequences of certain designs, which should be accounted for or minimized.
A material whose permeability is very much larger than 1 (from 60 to several thousand times 1), and which exhibits hysteresis phenomena.