Displacement Current absolutely different when applied in thermodynamics and in radio electronics.
Submitted by esaruoho on July 13, 2011 - 00:42
Maxwell's Displacement Current The term DISPLACEMENT CURRENT is absolutely different in its meaning when applied in thermodynamics and radio electronics. The notion was introduced by Maxwell, when he worked on developing an electromagnetic field theory to describe low currents generated, when charged particles are displaced in dielectrics. According to Maxwell, if any alternating magnetic field generates a vortex electrical field in the surrounding environment, there also has to exist an inverse: any alteration of an electrical field should cause the vortex magnetic field to occur in the surrounding environment. For example, when a capacitor is connected to a DC circuit there will be no current in the open circuit. If the same circuit is fed by an AC power supply, the system will have alternating current flowing through it. There exists an AC field between the plates of the capacitor being charged and of the capacitor being discharged, which is why, according to Maxwell, the capacitor will have displacement current flowing through it in the sections, where no conductors exist. Notable is that of all the physical properties attributed to the conduction current, Maxwell gave only one to the displacement current, and that is the ability to create a magnetic field in the surrounding environment. And this is where the similarities between the conductance and displacement currents both start and end. In a dielectric the displacement current consists of two components: displacement current in a vacuum and polarization current. The polarization current is explained by the ordered motion of bound electric charges in a dielectric, or, in other words, by displacement of charges in nonpolar molecules and rotation of dipoles in polar molecules. The displacement current exists also in conductors that have alternating conduction current flowing through them. But in this case it will be negligible if compared to the conductance current. That's why Maxwell introduced the notion of total current that is equal to the sum of conductance currents (as well as convection currents) and displacement currents. For the purpose of differentiation, the conductance current and displacement current are indicated by different symbols - I and j. By introducing the notion of displacement current and total current Maxwell also developed a totally new approach to closedness of AC circuits. The total current ...
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