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Persistent current is a perpetual electric current, not requiring an external power source. == In magnetized objects == In electromagnetism, all magnetizations can be seen as microscopic persistent currents. By definition a magnetization can be replaced by its corresponding microscopic form, which an electric current density: : This current is a bound current, not having any charge accumulation associated with it since it is divergenceless. What this means is that any permanently magnetized object, for example a piece of lodestone, can be considered to have persistent electric currents running throughout it (the persistent currents are generally concentrated near the surface). The converse is also true: any persistent electric current is divergence-free, and can therefore be represented instead by a magnetization. Therefore in the macroscopic Maxwell's equations, it is purely a choice of mathematical convenience, whether to represent persistent currents as magnetization or vice versa. In the microscopic formulation of Maxwell's equations, however, does not appear and so any magnetizations must be instead represented by bound currents. 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「Persistent current」の詳細全文を読む スポンサード リンク
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