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Electric potential energy, or electrostatic potential energy, is a potential energy (measured in joules) that results from conservative Coulomb forces and is associated with the configuration of a particular set of point charges within a defined system. An ''object'' may have electric potential energy by virtue of two key elements: its own electric charge and its relative position to other electrically charged ''objects''. The term "electric potential energy" is used to describe the potential energy in systems with time-variant electric fields, while the term "electrostatic potential energy" is used to describe the potential energy in systems with time-invariant electric fields. ==Definition== We define the electric potential energy of a system of point charges as the work required assembling this system of charges by bringing them close together, as in the system from an infinite distance. :The electrostatic potential energy, ''UE'', of one point charge ''q'' at position r in the presence of an electric field E is defined as the negative of the work ''W'' done by the electrostatic force to bring it from the reference position rref〔The reference zero is usually taken to be a state in which the individual point charges are very well separated ("are at infinite separation") and are at rest.〕 to that position r.〔Electromagnetism (2nd edition), I.S. Grant, W.R. Phillips, Manchester Physics Series, 2008 ISBN 0-471-92712-0〕〔Alternatively, it can also be defined as the work ''W'' done by the an external force to bring it from the reference position rref to some position r. Nonetheless, both definitions yield the same results.〕 :where E is the electrostatic field and ds is the displacement vector in a curve from the reference position rref to the final position r. The electrostatic potential energy can also be defined from the electric potential as follows: :The electrostatic potential energy, ''UE'', of one point charge ''q'' at position r in the presence of an electric potential is defined as the product of the charge and the electric potential. :where is the electric potential generated by the charges, which is a function of position r. 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「Electric potential energy」の詳細全文を読む スポンサード リンク
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