AC Electric field in the conducting media

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Discussion Overview

The discussion revolves around the behavior of AC electric fields in different conductive media, particularly focusing on the effects of frequency and conductivity on electric potential distribution. Participants explore the implications of skin depth and its relevance to the simulation results obtained using COMSOL.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant describes simulating AC electric fields in three media with varying conductivities and observes that at lower frequencies, the electric potential remains confined to high conductive media, while at certain higher frequencies, it penetrates low conductive media.
  • Another participant suggests investigating the concept of "skin depth" and its frequency dependence on conductivity, noting that conduction electrons respond to the oscillating field.
  • A participant mentions having assessed the skin depth, which is significantly larger than the dimensions of the model, leading to questions about its relevance in this context.
  • Concerns are raised regarding the unusually large skin depth calculated for the materials used, prompting inquiries about the accuracy of the simulation parameters and benchmarking against known materials.
  • Further discussion includes recommendations to use the RF module for higher frequency analyses, as the AC/DC module may not be suitable for such cases.

Areas of Agreement / Disagreement

Participants express differing views on the relevance of skin depth in the context of the simulation results, with some questioning the validity of the calculated values and others defending them based on the specific conductivities used.

Contextual Notes

There are unresolved questions regarding the accuracy of the simulation parameters and the implications of skin depth in the model, particularly given the large values calculated compared to the model dimensions.

ali hemmati
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Hello,

I have simulated AC electric field in multiple (in fact 3) media with COMSOL, a multiphysic solver.

The simulation took place with different frequencies of applied electric potential. Media have different conductivities. At lower frequencies, every thing is ok, I mean, electric potential is approximately equal in domain of high conductive medium and does not enter the low conductive ones. On the other hand, with increasing frequency, at a specific frequency, the potential "flows" into the low conductive medium.

This phenomenon is a little strange for me, as I am not completely familiar with the electromagnetics. Does anyone know what is happening here?

I have attached my pictures...
 

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You might want to look into what is known as "skin depth", and see its frequency dependence on the conductivity of the medium.

Remember, the conduction electrons react to the oscillating field. Something with higher conductivity can naively be thought of having "better moving electrons" than something with a lower conductivity.

Zz.
 
Thank you Zapper,

I have already assessed the skin depth of my model. Considering the conductivity and permittivity of the materials, skin depth is in order of tens of meters. The entire dimension of my model does not exceed millimeters! So, the skin depth may not have important role.

Bests,
Ali
 
ali hemmati said:
Thank you Zapper,

I have already assessed the skin depth of my model. Considering the conductivity and permittivity of the materials, skin depth is in order of tens of meters.

Whoa! Are you sure? What kind of a conductor is this that has THAT long of a skin depth? Have you benchmarked your codes to see if a similar material has the same parameters?

Zz.
 
Which module are you using?
 
Hi,

I used AC/DC module and used "frequency study".
 
Use the RF module for 1GHz. The AC/DC model does quasi-static analysis.

Consider joining the Comsol discussion forum if you are going to be doing a lot if this.

Cheers.
 
Whoa! Are you sure? What kind of a conductor is this that has THAT long of a skin depth? Have you benchmarked your codes to see if a similar material has the same parameters?

Zz.

Hi,

I have checked it again. It does not seem irrational! Conductivities are about 1e-13 S/m, 0.01 S/m, and 1 S/m. These conductivities bring about a high skin depth.
 

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