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Showing posts from December, 2012

Dictionary of Physics : S to Z

S
scalar a physical quantity that has magnitude but not direction scintillation flashes of light arising from the impact of high-energy particles (alpha particles) on a crystalline material second the unit of time secondary the output winding of a transformer semiconductor a material in which the resistance decreases as its temperature rises; its resistivity is higher than that of a conductor but lower than that of a resistor semiconductor, n-type a semiconductor in which 1 atom in a hundred thousand has been replaced by an element with 1 more electron than the base material semiconductor, p-type a semiconductor in which 1 atom in a hundred thousand has been replaced by an element with 1 less electron than the base material series circuit a circuit in which the components form a single conducting path shell burning a phase in a star’s life during which the fusion processes occur in a hot shell around an inert core that has not yet reached a high enough temperature for the next fusion process to start sh…

Dictionary of Physics : M to R

M
magnet, hard magnetic materials that do not lose their magnetism easily when the source of magnetism is removed, e.g. steel magnet, soft magnetic materials that are easy to magnetise but rapidly lose their magnetism; these are often used in electromagnets, e.g. iron magnetic field a region in which a magnetic force can be detected magnetic flux the lines of flux in a region of a magnetic field magnetic force a force due to the motion of a charged particle in a magnetic field magnetic levitation the use of the force between two opposing magnets to lift a body magnetic moment the small magnetic field produced by a spinning nucleus magnetic poles the points (north, south) of maximum magnetic flux magnetic resonance imaging the proton distribution in the body using strong imaging (MRI) magnetic fields and radiofrequency signals magnetopause the region separating the extended solar magnetic field (solar wind) from the Earth’s magnetosphere magnetosphere the region close to a planet that is dominated by…