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  • magistrates’ court (English law)
    in England and Wales, any of the inferior courts with primarily criminal jurisdiction covering a wide range of offenses from minor traffic violations and public-health nuisances to somewhat more serious crimes, such as petty theft or assault. Magistrates’ courts with similar jurisdictions may be found in certain large municipalities in the Unit...
  • Maglemosian industry (prehistoric culture)
    a tool culture of northern Europe dating from the postglacial period, approximately 9000 to 5000 bc. The Maglemosian industry was named after the bog (magle mose, “big bog,” in Danish) at Mullerup, Den., where evidence of the industry was first recognized. The industry was created by a Mesolithic (Middle Stone Age) forest people, who settled along rivers and lake...
  • maglev (technology)
    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 achieved by varying the frequency and voltage of a linear motor system embodied in the guideway and reacting with magnets on......
  • Maglič (mountain, Bosnia and Herzegovina)
    ...including the Plješivica, Grmeč, Klekovača, Vitorog, Cincar, and Raduša, run in a northwest-southeast direction. The highest peak, reaching 7,828 feet (2,386 metres), is Maglič, near the border with Montenegro. In the south and southwest is the Karst, a region of arid limestone plateaus that contain caves, potholes, and underground drainage. The uplands there....
  • Magloire, Paul E. (president of Haiti)
    Haitian military ruler (b. July 19, 1907, Cap-Haitien, Haiti—d. July 12, 2001, Port-au-Prince, Haiti), ruled Haiti from 1950 to 1956. The son of a general, Magloire rose through the ranks of the Haitian army to become a general himself by the late 1940s. He orchestrated the overthrow of Pres. Dumarsais Estimé in 1950 and installed himself as ruler. During his reign Magloire developed...
  • magma (rock)
    molten or partially molten rock from which igneous rocks form. It usually consists of silicate liquid, although carbonate and sulfide melts occur as well. Magma migrates either at depth or to the Earth’s surface and is ejected as lava. Suspended crystals and fragments of unmelted rock may be transported in the magma; dissolved volatiles may separate as bubbles and some liquid may crystalli...
  • magma chamber (geology)
    ...below the dikes totaling about 4.5 kilometres in thickness. Both of these include gabbros, which are essentially basalts with coarser mineral grains. These gabbro layers are thought to represent the magma chambers, or pockets of lava, that ultimately erupt on the seafloor. The upper gabbro layer is isotropic (uniform) in structure. In some places, this layer includes pods of plagiogranite, a......
  • magmatic cumulate (geology)
    ...process by which one or more minerals become locally concentrated (segregated) during the cooling and crystallization of a magma. Rocks formed as a result of magmatic segregation are called magmatic cumulates. While a magma may start as a homogeneous liquid, magmatic segregation during crystallization can produce an assemblage of cumulates with widely differing compositions. Extreme segregation...
  • magmatic segregation (geology)
    Magmatic segregation is a general term referring to any process by which one or more minerals become locally concentrated (segregated) during the cooling and crystallization of a magma. Rocks formed as a result of magmatic segregation are called magmatic cumulates. While a magma may start as a homogeneous liquid, magmatic segregation during crystallization can produce an assemblage of cumulates......
  • magmatic stoping (geology)
    Canadian-American geologist who independently developed the theory of magmatic stoping, whereby molten magma rises through the Earth’s crust and shatters, but does not melt, the surrounding rocks. The rocks, being denser than the magma, then sink, making room for the magma to rise. This theory was instrumental in explaining the structure of many igneous rock formations....
  • Magna Carta (England [1215])
    the charter of English liberties granted by King John in 1215 under threat of civil war and reissued with alterations in 1216, 1217, and 1225....
  • Magna Graecia (Greek cities, ancient Italy)
    group of ancient Greek cities along the coast of southern Italy; the people of this region were known to the Greeks as Italiotai and to the Romans as Graeci. The site of extensive trade and commerce, Magna Graecia was the seat of the Pythagorean and Eleatic systems of philosophy. Euboeans founded the first colonies, Pithecussae and Cumae, about 750 bc, and subsequently Spartans settl...
  • Magna Mater (ancient deity)
    ancient Oriental and Greco-Roman deity, known by a variety of local names; the name Cybele or Cybebe predominates in Greek and Roman literature from about the 5th century bc onward. Her full official Roman name was Mater Deum Magna Idaea (Great Idaean Mother of the Gods)....
  • magnacycle (geology)
    ...megacyclothems with some distinctive features have been called a hypercyclothem. Rock units, measuring several kilometres in thickness and spanning entire geologic systems, have been referred to as magnacycles. These larger units are of doubtful validity and restricted utility....
  • Magnalia Christi Americana (work by Mather)
    Cotton Mather wrote and published more than 400 works. His magnum opus was Magnalia Christi Americana (1702), an ecclesiastical history of America from the founding of New England to his own time. His Manuductio ad Ministerium (1726) was a handbook of advice for young graduates to the ministry: on doing good, on college love affairs, on poetry and music, and on style. His......
  • magnamycin (chemistry)
    ...chemical puzzle. During the 1950s, Woodward collaborated with the pharmaceutical company Pfizer, Inc., on the structural analysis of a new series of antibiotics: terramycin, aureomycin, and magnamycin....
  • Magnani, Anna (Italian actress)
    Italian actress, best known for her forceful portrayals of earthy, working-class women....
  • Magnasco, Alessandro (Italian painter)
    Italian painter of the late Baroque period distinguished for his landscapes and genre paintings....
  • Magnavox Corporation (American electronics company)
    ...of pinball games in this prototype, Bushnell and Alcorn installed it in a local bar, where it became an immediate success as a coin-operated game. After clearing a legal obstacle posed by the Magnavox Corporation’s hold on the patent for video games (discussed in the next section), Atari geared up to manufacture arcade consoles in volume, creating a new industry while also attracting......
  • Magne, Tour (tower, Nîmes, France)
    ...the best preserved. Like the amphitheatre, the building has had varied uses (town hall, private house, stable, and church) through the ages. It now houses a collection of Roman sculptures. The Tour Magne, atop a hill just outside the city, is the oldest Roman building, 92 ft high, but probably originally higher. Its original function is not known, but it was incorporated into the Roman......
  • Magnel, Gustave (American engineer)
    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) and two end spans of 22 metres (74 feet). Although it was plain in appearance, a local art jury responsible for final approval found that the slim lines......
  • Magnentius (Roman emperor)
    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)....
  • Magnes, Judah Leon (American rabbi)
    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 (chemical compound)
    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 Asia Minor), the oxide of magnesium, was shown to be an alkaline earth different from lime by the Scottish chemist Joseph Black in 1755; he observed that......
  • Magnesia (Turkey)
    city, western Turkey. It lies in the valley of the Gediz River (ancient Hermus River), below Mount Sipylus (Manisa Dağı), 20 miles (32 km) northeast of İzmir. It was called Magnesia ad Sipylum in ancient times, and the Magnetes of Thessaly are thought to have been its first inhabitants in the 12th century bc. It was taken by ...
  • Magnesia (chemical compound)
    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 Asia Minor), the oxide of magnesium, was shown to be an alkaline earth different from lime by the Scottish chemist Joseph Black in 1755; he observed that......
  • Magnesia ad Maeandrum (ancient city, Turkey)
    ancient inland city of Ionia, situated on a small tributary of the Maeander (Büyükmenderes) 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. Accounted an Aeolian city, it was never, despite its early prosperity, included in the Ionian League. Destroyed in the Cimmerian in...
  • Magnesia ad Sipylum (ancient city, Turkey)
    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 for the battle of winter 190/189 bc, described in Livy, xxxvii, when the Romans under Lucius Scipio decisively defeated Antiochus III an...
  • magnesia alba (chemical compound)
    ...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 next ring consists of sulfates of calcium and sodium (CaSO4 and Na2SO4...
  • Magnesia, Battle of (Greece [190 BC])
    ...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 fought with a heterogeneous army of 70,000 men against an army of 30,000 Romans and their allies. Although he could have continued the war in the e...
  • magnesia magma (chemical compound)
    The compounds of magnesium form an important group of chemicals. The best-known medical compounds are milk of magnesia, or magnesium hydroxide, which is used as an antacid or as a mineral supplement to maintain the body’s magnesium balance. The hydrous magnesium sulfate popularly known as Epsom salts, MgSO4 · 7H2O, is used as a laxative....
  • magnesia, milk of (chemical compound)
    The compounds of magnesium form an important group of chemicals. The best-known medical compounds are milk of magnesia, or magnesium hydroxide, which is used as an antacid or as a mineral supplement to maintain the body’s magnesium balance. The hydrous magnesium sulfate popularly known as Epsom salts, MgSO4 · 7H2O, is used as a laxative....
  • magnesia usta (chemical compound)
    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 Asia Minor), the oxide of magnesium, was shown to be an alkaline earth different from lime by the Scottish chemist Joseph Black in 1755; he observed that......
  • magnesioferrite (mineral)
    the mineral magnesium iron oxide, a member of the magnetite series of spinels....
  • Magnesiopolis (Turkey)
    city, western Turkey. It lies in the valley of the Gediz River (ancient Hermus River), below Mount Sipylus (Manisa Dağı), 20 miles (32 km) northeast of İzmir. It was called Magnesia ad Sipylum in ancient times, and the Magnetes of Thessaly are thought to have been its first inhabitants in the 12th century bc. It was taken by ...
  • magnesioriebeckite (mineral)
    magnesium-rich variety of the silicate mineral riebeckite....
  • magnesite (mineral)
    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 calcite. Notable deposits are those at Radenthein, Austria; the Liaotung Peninsula, Liaoning Province, China; and Clark...
  • magnesium (chemical element)
    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 element itself does not occur free. It was first isolated in 1808 by Sir Humphry Davy, who evaporated the mercury...
  • magnesium carbonate (chemical compound)
    ...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 next ring consists of sulfates of calcium and sodium (CaSO4 and Na2SO4...
  • magnesium chloride (chemical compound)
    ...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 Michael Faraday was the first to produce magnesium by the electrolysis of molten magnesium chloride. His experiments were......
  • magnesium cordierite (synthetic mineral compound)
    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 used as a semirefractory material because of its resistance to thermal shock....
  • magnesium deficiency (pathology)
    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 required for the synthesis of parathyroid hormone. About three-fourths of the mineral found in the body ...
  • magnesium germanate (chemical compound)
    ...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 and spinel structure. In the spinel structure, the oxygen atoms are arranged in cubic closest....
  • magnesium hydride (chemical compound)
    ...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 (300–700 °C [570–1,300 °F]) to produce hydrides of the....
  • magnesium hydroxide (chemical compound)
    ...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 pumped as a slurry, filtered, converted to magnesium chloride by reaction with hydrochloric acid, and dried in a series......
  • magnesium oxide (chemical compound)
    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 Asia Minor), the oxide of magnesium, was shown to be an alkaline earth different from lime by the Scottish chemist Joseph Black in 1755; he observed that......
  • magnesium processing
    preparation of the ore for use in various products....
  • magnesium sulfate (chemical compound)
    ...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 early as the residence of James I (1603–1625) at Nonsuch Park, becoming permanent in 1730. The famous Epsom meeting, at which the main races.....
  • magnesium tourmaline (mineral)
    a brown, magnesium-rich variety of tourmaline. See tourmaline....
  • magnesium tungstate (chemical compound)
    ...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 to four times of the operating voltage, needed to ionize the gas when starting....
  • magnet (physics)
    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 property. The most common was the property of diamagnetism, the name given to materials exhibiting a weak repulsion by both poles of a magnet. Some ...
  • Magnet Cove (Arkansas, United States)
    ...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; barite and titanium are the most important. Arkansas whetstones made from novaculite are regarded as among....
  • magnet ring (synchrotron)
    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. A means of increasing the energy without increasing the scale of the machines was provided by a demonstration in 1952 by......
  • Magnetherm process (metallurgy)
    ...(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 water-cooled copper electrode. The reduction reaction occurs at 1,600° C...
  • magnetic anomaly (geophysics)
    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 the boundaries between normally magnetized sea floor and sea floor magnetized in...
  • magnetic attraction (physics)
    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 magnetic forces exist among moving electric charges. The magnetic force between two ...
  • magnetic bottle
    ...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 in the middle. ...
  • magnetic bubble memory (computer science)
    ...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. A number of ferrites absorb microwave energy in only one direction or orientation; for this reason, they are used in microwave wave......
  • 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 ceramic materials and surveys their main commercial applications....
  • magnetic charge (physics)
    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 there is no evidence for the existence of magnetic monopoles, but they are interesting theoretically. In 1931 the English physicist P.A.M. Dirac proposed that......
  • magnetic circuit (electronics)
    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....
  • magnetic compass (navigational instrument)
    The magnetic compass...
  • magnetic confinement (physics)
    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 the magnetic field. This force causes electrons and ions to spiral about the direction of the magnetic line of force, thereby confining the particles. Wh...
  • magnetic core memory (computing)
    any of a class of computer memory devices consisting of a large array of tiny toruses of a hard magnetic material that can be magnetized in either of two directions (see computer memory)....
  • magnetic damping (physics)
    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 declination (compass)
    ...needle did not point true north from all locations but made an angle with the local meridian. This phenomenon was originally called by seamen the northeasting of the needle but is now called the variation or declination. For a time, compass makers in northern countries mounted the needle askew on the card so that the fleur-de-lis indicated true north when the needle pointed to magnetic......
  • magnetic dip (geophysics)
    ...Earth. The magnitude of the field projected in the horizontal plane is called H. This projection makes an angle D (for declination) measured positive from the north to the east. The dip angle, I (for inclination), is the angle that the total field vector makes with respect to the horizontal plane and is positive for vectors below the plane. It is the complement of the......
  • magnetic dipole (physics)
    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 sum of these effects may cancel so that a given type of atom may not be a magnetic dipole. If they do not f...
  • magnetic dipole moment (physics)
    ...is aligned along the same axis. The researchers passed a beam of silver atoms through a magnetic field, one that would deflect the atoms to one side or another according to the orientation of their magnetic moments. In their experiment Stern and Gerlach found only two deflections, not the continuous distribution of deflections that would have been seen if the magnetic moment had been oriented.....
  • magnetic disk (electronics)
    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 invented at IBM; consisting of 50 21-inch (53-cm) disks, it had a storage capacity of 5 megabytes. By the 1990s the standard HD diameter for PCs had shrunk to 3.5......
  • magnetic domain (physics)
    series of sudden changes in the size and orientation of ferromagnetic domains, or microscopic clusters of aligned atomic magnets, that occurs during a continuous process of magnetization or demagnetization. The Barkhausen effect offered direct evidence for the existence of ferromagnetic domains, which previously had been postulated theoretically....
  • magnetic drum (computing)
    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....
  • magnetic field (physics)
    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 direction of the field. Magnetic fields force moving, electrically charged particles in a circu...
  • magnetic field line (physics)
    ...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 in the circuit; and (2) the magnitude of the electromotive force equals the rate at which the flux of the magnetic field through the circuit......
  • magnetic field strength (physics)
    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 is unambiguous.) The definition of H is...
  • Magnetic Fields, The (work by Breton and Soupault)
    ...experimented with other revolutionary techniques. One result of their experimentation was the “automatic writing” of the jointly authored Les Champs magnétiques (1920; The Magnetic Fields), known as the first major Surrealist work. Soupault soon abandoned automatic writing to produce carefully crafted verses such as those in Westwego (1922) and......
  • magnetic flux (physics)
    ...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 in the circuit; and (2) the magnitude of the electromotive force equals the rate at which the flux of the magnetic field through the circuit......
  • magnetic flux density (physics)
    ...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 aligning process does not occur simultaneously or in step with the magnetizing field but lags behind it....
  • magnetic force (physics)
    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 magnetic forces exist among moving electric charges. The magnetic force between two ...
  • magnetic glass (material science)
    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 Fe0.8B0.2 iron-boron and Fe0.8B0.1Si0.1 iron-boron-silicon. They are readily formed as long metallic glass ribbons by melt spinning or as wide sheets by planar flow casting.......
  • magnetic head (magnetic recording)
    ...backing coated with a thin layer of tiny particles of magnetic powder, usually ferric oxide (Fe2O3) and to a lesser extent chromium dioxide (CrO2). The recording head of the tape deck consists of a tiny C-shaped magnet with its gap adjacent to the moving tape. The incoming sound wave, having been converted by a microphone into an electrical signal, produces a......
  • magnetic hyperfine structure (physics)
    ...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 the relative orientation of the magnetic field of the nucleus and electron range typically from 106 hertz to...
  • magnetic induction (physics)
    ...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 aligning process does not occur simultaneously or in step with the magnetizing field but lags behind it....
  • magnetic intensity (physics)
    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 is unambiguous.) The definition of H is...
  • magnetic iron ore (mineral)
    iron oxide mineral (FeFe2O4, or Fe3O4) that is the chief member of one of the series of the spinel group. Minerals in this series form black to brownish, metallic, moderately hard octahedrons and masses in igneous and metamorphic rocks and in granite pegmatites, stony meteorites, and high-temperature sulfide veins. The magnetite series...
  • Magnetic Island (island, Queensland, Australia)
    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 km) offshore from Townsville. Coral-fringed, wooded, and hilly, it is a fragment of a drowned coastal mountain rising to 1,631 feet (497 metres) above sea...
  • magnetic levitation (technology)
    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 achieved by varying the frequency and voltage of a linear motor system embodied in the guideway and reacting with magnets on......
  • magnetic map (geophysics)
    ...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 target area that may clearly indicate the size and extent of the anomalous body to the trained eye of the interpreting geophysicist. ...
  • magnetic mine (submarine 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 field. The pressure mine employs the principle that beneath every ship in motion in shallow water there is an area of reduced...
  • magnetic mirror (physics)
    static magnetic field that, within a localized region, has a shape such that approaching charged particles are repelled back along their path of approach....
  • magnetic moment (physics)
    ...is aligned along the same axis. The researchers passed a beam of silver atoms through a magnetic field, one that would deflect the atoms to one side or another according to the orientation of their magnetic moments. In their experiment Stern and Gerlach found only two deflections, not the continuous distribution of deflections that would have been seen if the magnetic moment had been oriented.....
  • magnetic monopole (physics)
    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 there is no evidence for the existence of magnetic monopoles, but they are interesting theoretically. In 1931 the English physicist P.A.M. Dirac...
  • magnetic mound (zoology)
    ...from the internal central portion (or nursery), which is composed of softer carton material. In northern Australia Amitermes meridionalis builds wedge-shaped mounds, called compass or magnetic mounds, that are 3 to 4 metres (9.8 to 13.1 feet) high, 2.5 metres (8.1 feet) wide, and 1 metre (3.2 feet) thick at the base. The long axis is always directed north-south, and the broad side......
  • Magnetic North Pole (geophysics)
    Between 1819 and 1827 Ross accompanied Sir William E. Parry’s Arctic voyages. On the second Arctic expedition of his uncle, Sir John Ross, he located the north magnetic pole on June 1, 1831. His own Antarctic expedition of 1839–43 was undertaken to conduct magnetic observations and to reach the south magnetic pole. Commanding the Erebus and Terror, he discovered the Ros...
  • magnetic observatory (geophysics)
    Magnetic observatories continuously measure and record the Earth’s magnetic field at a number of locations. In an observatory of this sort, magnetized needles with reflecting mirrors are suspended by quartz fibres. Light beams reflected from the mirrors are imaged on a photographic negative mounted on a rotating drum. Variations in the field cause corresponding deflections on the negative.....
  • magnetic permeability (physics)
    relative increase or decrease in the resultant magnetic field inside a material compared with the magnetizing field in which the given material is located; or the property of a material that is equal to the magnetic flux density B established within the material by a magnetizing field divided by the magnetic field strength H of the magnetizing field. Magnetic perm...
  • magnetic pigment (chemistry)
    ...(ZnCrO4) for corrosion control in primers, antimony oxide (Sb2O3) for fire-retardant coatings, and some compounds such as copper oxide (CuO) for barnacle control. Magnetic pigments, such as acicular iron oxide and chromium oxide pigments, are used in magnetic audio and video tapes for information storage....
  • magnetic polarization (physics)
    ...field, matter is either attracted or repelled in the direction of the gradient of the field. This property is described by the magnetic susceptibility of the matter and depends on the degree of magnetization of the matter in the field. Magnetization depends on the size of the dipole moments of the atoms in a substance and the degree to which the dipole moments are aligned with respect to......
  • magnetic pole (physics)
    region at each end of a magnet where the external magnetic field is strongest. A bar magnet suspended in the Earth’s magnetic field orients itself in a north–south direction. The north-seeking pole of such a magnet, or any similar pole, is called a north magnetic pole. The south-seeking pole, or any pole similar to it, is called a south magnetic pole. Unlike poles...
  • magnetic prospecting
    An understanding of rock magnetization is important in at least three different areas: prospecting, geology, and materials science. In magnetic prospecting, one is interested in mapping the depth, size, type, and inferred composition of buried rocks. The prospecting, which may be done from ground surface, ship, or aircraft, provides an important first step in exploring buried geologic......
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