| magnet | 1. The loadstone; a species of iron ore (the ferrosoferric or magnetic ore, Fe3O4) which has the property of attracting iron and some of its ores, and, when freely suspended, of pointing to the poles; called also natural magnet. "Dinocrates began to make the arched roof of the temple of Arsinoe all of magnet, or this loadstone." (Holland) "Two magnets, heaven and earth, allure to bliss, The larger loadstone that, the nearer this." (Dryden) 2. <physics> A bar or mass of steel or iron to which the peculiar properties of the loadstone have been imparted; called, in distinction from the loadstone, an artificial magnet. An artificial magnet, produced by the action of a voltaic or electrical battery, is called an electromagnet. <physics> Field magnet, a magnet used for producing and maintaining a magnetic field; used especially of the stationary or exciting magnet of a dynamo or electromotor in distinction from that of the moving portion or armature. Origin: OE. Magnete, OF. Magnete, L. Magnes, -etis, Gr. A magnet, metal that looked like silver, prop, Magnesian stone, fr. Gr, a country in Thessaly. Cf. Magnesia, Manganese. Source: Websters Dictionary (01 Mar 1998) |
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| magnet reaction | A reaction seen in an animal deprived of its cerebellum; when the animal is placed upon its back and the head strongly flexed, the four limbs become flexed in all their joints. Due to stimulation of receptors in the deep layers of the skin, light pressure made upon a toe-pad with the finger causes reflex contraction of the limb extensors; the limb is thus pressed gently against the finger, and when the finger is withdrawn slightly, the experimenter has the sensation that his finger is raising the limb or drawing it out as by a magnet. (05 Mar 2000) |
| magnet reflex | A reaction seen in an animal deprived of its cerebellum; when the animal is placed upon its back and the head strongly flexed, the four limbs become flexed in all their joints. Due to stimulation of receptors in the deep layers of the skin, light pressure made upon a toe-pad with the finger causes reflex contraction of the limb extensors; the limb is thus pressed gently against the finger, and when the finger is withdrawn slightly, the experimenter has the sensation that his finger is raising the limb or drawing it out as by a magnet. (05 Mar 2000) |
| magnetic | 1. A magnet. "As the magnetic hardest iron draws." (Milton) 2. Any metal, as iron, nickel, cobalt, etc, which may receive, by any means, the properties of the loadstone, and which then, when suspended, fixes itself in the direction of a magnetic meridian. Source: Websters Dictionary (01 Mar 1998) |
| magnetic attraction | The force that draws iron or steel toward a magnet. (05 Mar 2000) |
| magnetic axis | <physics> This typically refers to the location of the innermost flux surface in a toroidal device, the one which encloses no volume and has therefore degenerated from a flux surface into a single field line. Roughly, the circle through the middle of the dough of the donut. Additionally, in systems with magnetic islands (see entry below), each island has a local magnetic axis, distinct from the overall magnetic axis of the torus. (09 Oct 1997) |
| magnetic confinement | <physics> Use of magnetic fields to confine a plasma. (Confinement involves restricting the volume of the plasma and/or restricting particle or energy transport from the centre of the plasma to the edge.) (09 Oct 1997) |
| magnetic confinement fusion | <physics> Method of fusion which uses magnetic fields / magnetic bottles to confine a hot plasma until fusion occurs. (09 Oct 1997) |
| magnetic field | The sphere of influence of a magnet. (05 Mar 2000) |
| magnetic field gradient | In magnetic resonance imaging, a magnetic field that varies with location, superimposed on the uniform field of the magnet, to alter the resonant frequency of nuclei and allow recovery of their spatial position. Synonym: field gradient. (05 Mar 2000) |
| magnetic implant | A tissue-tolerated, magnetised metal placed within the bone to aid in denture retention; a similar magnet is placed in the overlying denture to complete the field. (05 Mar 2000) |
| magnetic inertia | <physics> A lagging or retardation of the effect, when the forces acting upon a body are changed, as if from velocity or internal friction; a temporary resistance to change from a condition previously invuced, observed in magnetism, thermoelectricity, etc, on reversal of polarity. Origin: NL, fr. Gr. To be behind, to lag. Source: Websters Dictionary (01 Mar 1998) |
| magnetic island | <physics> A magnetic topology near a rational surface where the flux surface is broken up into tubes which are not connected with each other poloidally. Islands may develop in non-ideal magnetohydrodynamic fluids, where electrical resistance becomes important and magnetic field lines are no longer frozen-in to the fluid. Then magnetic tearing and reconnection may allow field lines to link up and form islands with a local magnetic axis in a narrow region near a rational surface. (See also magnetohydrodynamic, frozen-in law). The development of islands may be caused by a small perturbation, whether internal or external, whether deliberate or accidental, and is usually associated with enhanced transport (i.e., reduced confinement). The centres of the islands are magnetic O-points, while the boundaries between islands are marked by X-points. (09 Oct 1997) |
| magnetic mach number | <physics> A dimensionless number equal to the ratio of the velocity of a fluid to the velocity of Alfven waves in that fluid. (13 Nov 1997) |
| magnetic moment | <physics> (a) A vector associated with a magnet, current loop, or particle, the cross product of this vector with the magnetic field is equal to the torque which the field exerts on the system. (b) The adiabatic invariant associated with the rapid gyromotion of a charged particle in a slowly varying magnetic field. (The value of the magnetic moment in sense (b) is the magnitude of the vector in sense (a).) (13 Nov 1997) |
| superconducting magnet | A magnet whose coils are cooled, usually with liquid helium, to a temperature at which the metal becomes superconducting, effectively removing all electrical resistance. (05 Mar 2000) |
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