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Magnetic levitation, maglev, or magnetic suspension is a method by which an object is suspended with no support other than magnetic fields. Magnetic force is used to counteract the effects of the gravitational acceleration and any other accelerations. The two primary issues involved in magnetic levitation are ''lifting forces'': providing an upward force sufficient to counteract gravity, and ''stability'': ensuring that the system does not spontaneously slide or flip into a configuration where the lift is neutralized. Magnetic levitation is used for maglev trains, contactless melting, magnetic bearings and for product display purposes. ==Lift== Magnetic materials and systems are able to attract or press each other apart or together with a force dependent on the magnetic field and the area of the magnets, For example, the simplest example of lift would be a simple dipole magnet positioned in the magnetic fields of another dipole magnet, oriented with like poles facing each other, so that the force between magnets repels the two magnets.〔(calculator ) for force between two disc magnets (retrieved April 16, 2014)〕 Essentially all types of magnets have been used to generate lift for magnetic levitation; permanent magnets, electromagnets, ferromagnetism, diamagnetism, superconducting magnets and magnetism due to induced currents in conductors. To calculate the amount of lift, a magnetic pressure can be defined. For example, the magnetic pressure of a magnetic field on a superconductor can be calculated by: : where is the force per unit area in pascals, is the magnetic field just above the superconductor in teslas, and = 4π×10−7 N·A−2 is the permeability of the vacuum.〔Lecture 19 MIT 8.02 Electricity and Magnetism, Spring 2002〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Magnetic levitation」の詳細全文を読む スポンサード リンク
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