Displacement current vs eddy current

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Discussion Overview

The discussion centers on the physical differences between displacement current and eddy current, particularly in the context of geophysics. Participants explore the definitions, implications, and applications of these concepts, with a focus on their relevance to electromagnetic phenomena in the ground.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant seeks clarification on the definitions of displacement current and eddy current, noting that eddy currents can be induced in the ground by a primary magnetic field, which creates secondary magnetic fields.
  • Another participant explains that displacement current is a mathematical concept introduced by Maxwell to describe changes in the electric field, asserting that it does not involve actual charge movement and can occur even in a vacuum.
  • The same participant contrasts this with eddy currents, which are described as real currents resulting from the movement of charges in a material due to changing magnetic fields.
  • A participant questions the relationship between induced polarization and displacement effects, indicating a need for further clarification on whether they represent the same physical phenomenon.

Areas of Agreement / Disagreement

Participants express differing views on the nature of displacement current, with one asserting it is merely a mathematical tool while another seeks to understand its physical implications. The discussion remains unresolved regarding the relationship between induced polarization and displacement effects.

Contextual Notes

The discussion highlights potential confusion surrounding the definitions and implications of displacement and eddy currents, as well as the relationship between these concepts and induced polarization. There are indications of missing assumptions and varying interpretations of the terms used.

Who May Find This Useful

This discussion may be of interest to students and professionals in geophysics, electrical engineering, and related fields who are exploring electromagnetic theory and its applications.

VaikGeomatics
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Hello,
I'm new on this forum. I hope I could help some of you next days. But today I have a question for you.
I have a geophysics oral exam on wednesday.
The course material is not clear, and I don't understand the wikipedia pages.

What is the physical difference between displacement current and eddy current ?
I know that eddy currents can be induced in the ground under the effect of primary magnetic field. Then, they create secondary magnetic fields.

But I don't get the meaning of displacement current. I thought displacement currents were explained by polarized grains in the ground. Due to magnetic and electric variations charged particules move within the ground. These movements induce displacement currents.
Is that right ?

So the difference would be that eddy current is not due to particule movement but displacement current is ?
By the way is induced polarization and displcement effect the same physical phenomen ?

Thanks a lot for you help.
V
 
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Displacement current is actually a misnomer. Displacement currents aren't actual currents. They are merely a mathematical tool to understand what is going on when the electric field changes. As Maxwell found out, when there are changes in the electric field, the magnetic field also changes in a way that could be explained if we assumed there were electric currents, called displacement currents. But there's no movement of charges (displacement currents may happen even in vacuum), so they aren't really a current.

Eddy currents, on the other hand, are real currents. They occur when the magnetic field changes (notice that displacement currents are the result of changes in the electric field). In an eddy current, charges move around in a material, so it is a current.

Take a look at http://ocw.mit.edu/courses/physics/8-02-electricity-and-magnetism-spring-2002/video-lectures/ . On Lecture 19, he gives the best explanation of what a displacement current is.
 
Thanks a lot. I m going to read your post and watch the video carrefully.
 
you said you have an oral exam of geophysics , so what kind of your study, geophysics or geology, Waiting for your kindly reply.
 
I'm studying GIS for environmental purposes. But that's more about geophysics than geology, despite it's not really geophysics.
Thanks "Acut" I got a nice grade for my oral exam.
 
VaikGeomatics said:
I'm studying GIS for environmental purposes. But that's more about geophysics than geology, despite it's not really geophysics.
Thanks "Acut" I got a nice grade for my oral exam.

You're welcome! I'm glad that information helped!
 

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