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Nikitin
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I know and fully understand the mathematical definition of it. But what's the physical explanation? Is it something like "preservation of current" or something?
Displacement current is a virtual current - a device that is added to Ampere's law to make Ampere's law work. Maxwell thought a vacuum behaved like a dielectric and imagined that there was something in the vacuum between the plates of a capacitor that behaved like little moving charges. But there isn't. So there is no physical explanation as a current.Nikitin said:I know and fully understand the mathematical definition of it. But what's the physical explanation? Is it something like "preservation of current" or something?
phyzguy said:There's a great explanation of the displacement current and why it has to be there in "The Feynman Lectures on Physics" Vol 2, Chapter 18.
I attached a pdf below.
That is partially true, if the displacement current occurs inside a simple dielectric. Then part of the displacement current is due to changing polarization state of the dielectric, so electric current is involved, and this can be called 'source'.It can be viewed as a 'source' for the magnetic field inside and around a capacitor for eg.
This is bit problematic. Actually the changing electric and magnetic fields always occur together. Since they are two faces of one force acting on the charges, it is not good to say that one produces the other. Rather the electric charges and currents produce both fields - this corresponds better both to physical and mathematical usage of the term 'source'.The idea is that magnetic fields can be produced not just by electric currents but by changing electric fields as well.
Displacement current is a concept in electromagnetism that describes the flow of electric charge in a region where there is a changing electric field. It is similar to conduction current, which is the movement of electric charge through a conductor, but it occurs in regions where there is no physical movement of charges.
The main difference between displacement current and conduction current is that displacement current does not involve the actual movement of charges, whereas conduction current does. In displacement current, the electric field itself is changing, while in conduction current, the charges are physically moving through a conductor.
Displacement current is important because it is a fundamental concept in electromagnetism that helps explain the behavior of electric and magnetic fields. It is also a key component in Maxwell's equations, which are fundamental equations in the study of electromagnetism.
Displacement current is closely related to electromagnetic waves. In fact, displacement current is one of the key components in the generation of electromagnetic waves. When an alternating current flows through a conductor, it creates a changing electric field, which in turn generates a changing magnetic field. This changing magnetic field then produces a changing electric field, and the process repeats, creating an electromagnetic wave.
Displacement current itself cannot be measured directly, but its effects can be observed and measured. For example, displacement current can be indirectly measured through its influence on the magnetic field in a region. It is also measured and taken into account in various practical applications, such as in the design of electronic circuits and antennas.