Encyclopædia Britannica Australia -

Encyclopedias since 1768

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Magnel, Gustave ... magnetic monopole

Magnel, Gustave: (from the article "bridge") The first major bridge made of prestressed concrete in the United States, the Walnut Lane Bridge (1950) in Philadelphia, was designed by Gustave Magnel and features three simply supported girder spans with a centre span of 48 metres (160 feet) ...
Magnentius: usurping Roman emperor from Jan. 18, 350, to Aug. 11, 353. His career forms one episode in the struggles for imperial power that occurred after the death of Constantine the Great (ruled 306-337). [2 Related Articles]
Magnes, Judah Leon: rabbi, religious leader, prime founder and first president of the Hebrew University of Jerusalem, and a Zionist who came to favour a binational Arab-Jewish state.
Magnesia ad Maeandrum: ancient inland city of Ionia, situated on a small tributary of the Maeander (Buyukmenderes) River about 12 miles southeast of Ephesus. According to Strabo, it was founded by some Thessalian Magnetes, who had collected fellow settlers from Crete en route. ...
Magnesia ad Sipylum: city in ancient Lydia, just south of the Hermus (Gediz) River. Though lying in a rich district near prehistoric regions associated with Niobe and Tantalus, and itself going back to the 5th century BC, it is of little importance except ...
Magnesia, Battle of: (from the article "Antiochus III") ...negotiate on the basis of Rome's previous demands, but the Romans insisted that he first evacuate the region west of the Taurus Mountains. When Antiochus refused, he was decisively defeated in the Battle of Magnesia near Mt. Sipylus, where he ...
magnesioferrite: (from the article "magnesioferrite") the mineral magnesium iron oxide, a member of the magnetite (q.v.) series of spinels.magnetitemagnetite...metallic, moderately hard octahedrons and masses in igneous and
magnesioriebeckite: (from the article "magnesioriebeckite") magnesium-rich variety of the silicate mineral riebeckite (q.v.).riebeckiteriebeckite...in the amphibole family. It forms part of a solid-solution series tha
magnesite: the mineral magnesium carbonate (MgCO₃), a member of the calcite group of carbonate minerals that is a principal source of magnesium. The mineral has formed as an alteration product from magnesium-rich rocks or through the action of magnesium-containing solutions upon ... [4 Related Articles]
magnesium: chemical element, one of the alkaline-earth metals of main Group IIa of the periodic table, the lightest structural metal. Known originally through compounds such as Epsom salts (the sulfate), magnesia (the oxide), and magnesia alba (the carbonate), the silvery white ... [19 Related Articles]
magnesium carbonate: (from the article "playa") ...the centre. The crystallization of these salts can be compared with the evaporation of brine in a dish. The first precipitates from the evaporating brine are calcium carbonate (CaCO₃) and magnesium carbonate (MgCO₃). These form the outer "bathtub ring." The ...
magnesium chloride: (from the article "magnesium processing") ...moist magnesium sulfate, using mercury as a cathode. The first metallic magnesium, however, was produced in 1828 by the French scientist A.-A.-B. Bussy. His work involved the reduction of molten magnesium chloride by metallic potassium. In 1833 the English scientist ...
magnesium cordierite: (from the article "cordierite") The natural mineral has little commercial use. When clear, cordierite is sometimes cut as a gem; the stones from the gem gravels of Sri Lanka have been called water sapphires. Synthetic magnesium cordierite has a low thermal expansion and is ...
magnesium deficiency: condition in which magnesium is insufficient or is not utilized properly. Magnesium is a mineral that is essential to a variety of cellular metabolic reactions and sometimes has the ability to replace a portion of body calcium. It is also ...
magnesium germanate: (from the article "olivine") ...and garnetiferous peridotite that contain olivines as their most abundant minerals, it is important to establish their behaviour when subjected to high pressures. Study of the olivine-like compound magnesium germanate, Mg₂GeO₄, showed that it has polymorphs that have both olivine ...
magnesium hydride: (from the article "hydride") ...H⁻. The saline hydrides are generally considered those of the alkali metals and the alkaline-earth metals (with the possible exception of beryllium hydride, BeH₂, and magnesium hydride, MgH₂). These metals enter into a direct reaction with hydrogen at elevated temperatures ...
magnesium hydroxide: (from the article "magnesium processing") ...solutions. Partly dehydrated magnesium chloride can be obtained by the Dow process, in which seawater is mixed in a flocculator with lightly burned reactive dolomite. An insoluble magnesium hydroxide precipitates to the bottom of a settling tank, whence it is ...
magnesium oxide: (from the article "Table 1: Raw Materials Used in the Manufacture of Portland Cement") The earliest known alkaline earth was lime (Latin: calx), which is now known to be calcium oxide; it was used in ancient times in the composition of mortar. Magnesia (the name derives probably from the ancient district of Magnesia in ...
magnesium processing: preparation of the ore for use in various products. [1 Related Articles]
magnesium sulfate: (from the article "Epsom and Ewell") ...county of Surrey, England, at the foot of the North Downs, on the southwestern periphery of Greater London. It became important with the discovery (c. 1618) of mineral springs (from which Epsom salts were named). Horse racing began there as ...
magnesium tungstate: (from the article "fluorescent lamp") ...The inside of the tube is coated with phosphors, substances that absorb ultraviolet radiation and fluoresce (reradiate the energy as visible light). Two common phosphors are zinc silicate and magnesium tungstate. A starter and ballast provide the extra voltage, up ...
magnet: any material capable of attracting iron and producing a magnetic field outside itself. By the end of the 19th century all the known elements and many compounds had been tested for magnetism, and all were found to have some magnetic ... [18 Related Articles]
Magnet Cove: (from the article "Arkansas") ...plants. Experimental use of lignite in coal-fired electrical generating stations offers the possibility of extensive commercial development of the widespread lignite deposits in southern Arkansas. Magnet Cove, near Hot Springs, contains more than 40 different minerals in one small valley; ...
magnet ring: (from the article "particle accelerator") The progress in research made possible by raising the energies of protons led to the building of successively larger accelerators; the trend was ended only by the cost of fabricating the huge magnet rings required-the largest weighs approximately 40,000 tons. ...
Magnetherm process: (from the article "magnesium processing") ...(aluminum oxide, Al₂O₃) to the charge, the melting point can be reduced to 1,550°-1,600° C (2,825°-2,900° F). This technique, utilized in the Magnetherm process, has the advantage that the liquid slag can be heated directly by electric current through a ...
magnetic anomaly: (from the article "paleogeography") Earth's magnetic field has another important property. Like the Sun's magnetic field, Earth's magnetic field periodically "flips," or reverses polarity-that is, the North and South poles switch places. Fluctuations, or anomalies in the intensity of the magnetic field, occur at ...
magnetic bottle: (from the article "magnetic mirror") ...along its original path. The exact location at which this mirroring occurs depends only upon the initial pitch angle describing its helical path. Two such magnetic mirrors can be arranged to form a magnetic bottle that can trap charged particles ...
magnetic bubble memory: (from the article "ferrite") ...cores of digital computers, since it enables a tiny ferrite ring to store binary bits of information. Another type of computer memory can be made of certain single-crystal ferrites in which tiny magnetic domains called bubbles can be individually manipulated. ...
magnetic ceramics: oxide materials that exhibit a certain type of permanent magnetization called ferrimagnetism. Commercially prepared magnetic ceramics are used in a variety of permanent magnet, transformer, telecommunications, and information recording applications. This article describes the composition and properties of the principal ...
magnetic charge: (from the article "magnetic monopole") hypothetical particle with a magnetic charge, a property analogous to an electric charge. As implied by its name, the magnetic monopole consists of a single pole, as opposed to the dipole, which is comprised of two magnetic poles. As yet ...
magnetic circuit: closed path to which a magnetic field, represented as lines of magnetic flux, is confined. In contrast to an electric circuit through which electric charge flows, nothing actually flows in a magnetic circuit. [1 Related Articles]
magnetic compass: (from the article "navigation") The magnetic compassdevelopment and usecompass The oldest and most familiar type of compass is the magnetic compass, which is used in different forms in aircraft, ships, and land vehicles and ...
magnetic confinement: (from the article "nuclear fusion") In magnetic confinement the particles and energy of a hot plasma are held in place using magnetic fields. A charged particle in a magnetic field experiences a Lorentz force that is proportional to the product of the particle's velocity and ...
magnetic damping: (from the article "damping") In magnetic damping, energy of motion is converted to heat by way of electric eddy currents induced in either a coil or an aluminum plate (attached to the oscillating object) that passes between the poles of a magnet.
magnetic dipole: generally a tiny magnet of microscopic to subatomic dimensions, equivalent to a flow of electric charge around a loop. Electrons circulating around atomic nuclei, electrons spinning on their axes, and rotating positively charged atomic nuclei all are magnetic dipoles. The ... [6 Related Articles]
magnetic disk: (from the article "computer memory") Magnetic disks are coated with a magnetic material such as iron oxide. There are two types: hard disks made of rigid aluminum or glass, and removable diskettes made of flexible plastic. In 1956 the first magnetic hard drive (HD) was ...
magnetic drum: (from the article "magnetic recording") Such magnetic recording mediums as drums and ferrite cores have been used for data storage since the early 1950s. A more recent development is the magnetic bubble memory devised in the late 1970s at Bell Telephone Laboratories.types of computer memory
magnetic field: region in the neighbourhood of a magnet, electric current, or changing electric field, in which magnetic forces are observable. Magnetic fields such as that of the Earth cause magnetic compass needles and other permanent magnets to line up in the ... [74 Related Articles]
magnetic field strength: (from the article "magnetism") The field H is called the magnetic intensity and, like M, is measured in units of amperes per metre. (It is sometimes also called the magnetic field, but the symbol H ...
magnetic flux: (from the article "International System of Units (SI)") ...discovery in 1831 of the phenomenon of magnetic induction is one of the great milestones in the quest toward understanding and exploiting nature. Stated simply, Faraday found that (1) a changing magnetic field in a circuit induces an electromotive force ...
magnetic flux density: (from the article "International System of Units (SI)") ...H, caused by the current forces some or all of the atomic magnets in the material to align with the field. The net effect of this alignment is to increase the total magnetic field, or magnetic flux density B. The ...
magnetic force: attraction or repulsion that arises between electrically charged particles because of their motion; the basic force responsible for the action of electric motors and the attraction of magnets for iron. Electric forces exist among stationary electric charges; both electric and ... [4 Related Articles]
magnetic glass: (from the article "amorphous solid") The last entry in the Table is an application of metallic glasses having magnetic properties. These are typically iron-rich amorphous solids with compositions such as Fe_0.8B_0.2 iron-boron and Fe_0.8B_0.1Si_0.1 iron-boron-silicon. They are readily formed as long metallic glass ribbons by ...
magnetic hyperfine structure: (from the article "spectroscopy") ...nucleus and the magnetic field produced by the surrounding electrons. This additional structure of an atom's levels or of spectral lines caused by the magnetic properties of its nucleus is called magnetic hyperfine structure. Separations between levels differing only in ...
Magnetic Island: island in the Cumberland Islands, off the coast of northeastern Queensland, Australia, in Halifax Bay, an inlet of the Coral Sea. It is one of the most easily accessible islands of the Great Barrier Reef, being only 5 miles (8 ...
magnetic levitation: (from the article "railroad") From the 1970s, interest in an alternative high-speed technology centred on magnetic levitation, or maglev. This vehicle rides on an air cushion created by electromagnetic reaction between an on-board device and another embedded in its guideway. Propulsion and braking are ...
magnetic map: (from the article "magnetic survey") ...makes measurements at each station on the grid. The corrected data he records is then entered on a scale drawing of the grid, and contour lines are drawn between points of equal intensity to give a magnetic map of the ...
magnetic mine: (from the article "mine") ...mine's surface and activate the firing mechanism when the hull of a passing ship strikes them. Other types of detonators used on submarine mines include magnetic, pressure, and acoustic ones. The magnetic mine is triggered by the approaching ship's magnetic ...
magnetic mirror: static magnetic field that, within a localized region, has a shape such that approaching charged particles are repelled back along their path of approach. [3 Related Articles]
magnetic moment: (from the article "Physical Sciences") ...physicists headaches was the muon. The generally accepted theory of fundamental particles, called the Standard Model, very precisely predicted the value of a property of these particles called the magnetic moment. Physicists at the Brookhaven National Laboratory, Upton, N.Y., conducted ...
magnetic monopole: hypothetical particle with a magnetic charge, a property analogous to an electric charge. As implied by its name, the magnetic monopole consists of a single pole, as opposed to the dipole, which is comprised of two magnetic poles. As yet ...