无磁场参与的时变电场

Time-Varying Electric Field not Accompanied by Magnetic Field

一般而言,时变场情况下电场和磁场是相互作用且同时存在的。依据电磁感应定律,容易理解无电场伴随的纯粹时变磁场是不存在。然而,本文强调,纯粹的时变电场是可以存在的。例如,在导电媒质的电荷弛豫过程中,如果传导电流与位移电流正好处处相互抵消,则此时可以不出现磁场。在这种场中,没有电磁能量的流动,空间储存的电场能量就地通过欧姆损耗转化为热能。

Generally speaking,in the case of time-varying field,both electric field and magnetic field components interact with each other and exist simultaneously. It is easy to understand that pure time-varying magnetic field may not exist according to Faradayˊs electromagnetic induction law. However,on the other hand,we show that pure time-varying electric field may exist in some cases. For example,in the process of electric charge relaxation in con-ductive medium,if both the conduction current and the displacement current cancel each other out completely, then the magnetic field component does not exist. For this case,there is no electromagnetic energy flow,and the e-lectric field energy stored in space is transferred completely into thermal energy locally by the Ohm loss mechanism.