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A magnetic circuit is made up of one or more closed loop paths containing a magnetic flux. The flux is usually generated by permanent magnets or electromagnets and confined to the path by magnetic cores consisting of ferromagnetic materials like iron, although there may be air gaps or other materials in the path. Magnetic circuits are employed to efficiently channel magnetic fields in many devices such as electric motors, generators, transformers, relays, lifting electromagnets, SQUIDs, galvanometers, and magnetic recording heads. The concept of a "magnetic circuit" exploits a one-to-one correspondence between the equations of the magnetic field in an unsaturated ferromagnetic material to that of an electrical circuit. Using this concept the magnetic fields of complex devices such as transformers can be quickly solved using the methods and techniques developed for electrical circuits. Some examples of magnetic circuits are: * horseshoe magnet with iron keeper (low-reluctance circuit) * horseshoe magnet with no keeper (high-reluctance circuit) * electric motor (variable-reluctance circuit) ==Magnetomotive force (MMF)== (詳細はEMF) drives a current of electrical charge in electrical circuits, magnetomotive force (MMF) 'drives' magnetic flux through magnetic circuits. The term 'magnetomotive force', though, is a misnomer since it is not a force nor is anything moving. It is perhaps better to call it simply MMF. In analogy to the definition of EMF, the magnetomotive force around a closed loop is defined as: : The MMF represents the potential that a hypothetical magnetic charge would gain by completing the loop. The magnetic flux that is driven is not a current of magnetic charge; it merely has the same relationship to MMF that electric current has to EMF. (See microscopic origins of reluctance below for a further description.) The unit of magnetomotive force is the ampere-turn (At), represented by a steady, direct electric current of one ampere flowing in a single-turn loop of electrically conducting material in a vacuum. The gilbert (Gb), established by the IEC in 1930,〔(International Electrotechnical Commission )〕 is the CGS unit of magnetomotive force and is a slightly smaller unit than the ampere-turn. The unit is named after William Gilbert (1544–1603) English physician and natural philosopher. :〔Matthew M. Radmanesh, ''The Gateway to Understanding: Electrons to Waves and Beyond'', (p. 539 ), AuthorHouse, 2005 ISBN 1418487406.〕 The magnetomotive force can often be quickly calculated using Ampère's law. For example, the magnetomotive force of long coil is: : where ''N'' is the number of turns and ''I'' is the current in the coil. In practice this equation is used for the MMF of real inductors with ''N'' being the winding number of the inducting coil. 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 circuit」の詳細全文を読む スポンサード リンク
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