Electrostatic induction

It is also called electrostatic induction. When a conductor is brought close to an electric charge or a charged object, a charge of the opposite sign appears on the side of the conductor closest to the charge, and a charge of the same sign appears on the side of the conductor farthest from the charge. In other words, when a conductor is placed in an electric field, the charges on the conductor move and the entire conductor becomes equipotential again. The figure shows the electric field that results from electrostatic induction when a conductor ball is placed next to a point charge. Electrostatic induction occurs because like charges repel and unlike charges attract each other. In this sense, electrostatic induction is the same as the polarization phenomenon that occurs in dielectrics. However, in the case of a conductor, charges can move freely on the conductor, so if two conductors are first brought into contact to cause electrostatic induction, as in (a) of the figure , and then the two conductors are separated in this state, each conductor will be charged with an opposite sign, as in (b) of the figure .

[Shigeo Yamaguchi]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

静電感応ともいう。導体を電荷または帯電した物体に近づけると、導体の電荷に近い側には電荷と反対符号の電荷が現れ、導体の電荷から遠い側には電荷と同符号の電荷が現れる現象をいう。別の言い方をすれば、導体を電界の中に置いたとき、導体上の電荷が移動して導体全体がふたたび等電位となる現象である。図は、点電荷のそばに導体球を置いたときの静電誘導の結果生ずる電界を示す。静電誘導は、同種の電荷は反発し、異種の電荷は引き合うという性質からおこる。この意味で、静電誘導は誘電体におこる分極現象と同じ性質のものである。しかし、導体の場合、電荷は導体上を自由に動くことができるので、図の(a)のように、初め二つの導体を接触させて静電誘導をおこさせておき、その状態で二つの導体を切り離すと、図の(b)のように各導体は反対符号の電荷を帯電するようになる。

［山口重雄］

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