Modeling of resistance in a rectangular sheet with COMSOL

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Discussion Overview

The discussion revolves around modeling the electrical resistance of a rectangular conductive sheet using COMSOL/Femlab. Participants explore boundary conditions, potential application, and numerical simulation techniques relevant to this problem.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • David describes the challenge of calculating electrical resistance between a corner of a conductive sheet and other points, questioning the appropriate boundary conditions and potential application.
  • One participant suggests that the potential may become singular at points where current is introduced or removed, recommending the use of finite-sized electrodes to improve numerical behavior.
  • Another participant mentions the possibility of setting potential along boundaries and suggests defining a small square electrode with a specific voltage, while also needing to establish a ground point.
  • David expresses a need for a faster solution to calculate resistance across a grid of points, indicating that scripting the calculations may be cumbersome.
  • A suggestion is made to contact a specific individual at COMSOL for assistance, indicating the potential for external support in resolving the issue.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the best approach to apply potential and boundary conditions, indicating that multiple competing views and uncertainties remain regarding the modeling setup.

Contextual Notes

Participants highlight limitations in their current understanding of COMSOL, particularly regarding the application of boundary conditions and the behavior of potentials at specific points. There is also uncertainty about the most efficient method for calculating resistance across a grid.

Who May Find This Useful

Individuals interested in numerical simulations of electrical properties in conductive materials, particularly those using COMSOL or similar software for modeling and analysis.

sunshine09
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Hi,

I have got a simple problem which makes me struggle.
I have a rectangular thin conductive sheet (2D) of width w, height h
and conductivity suspended in air.
I would like to calculate with COMSOL/Femlab the electrical resistance between one of the corners of the conductive sheet and any other point on the sheet?
I selected the 'conductive media DC' mode in 2D. I am not sure what
boundary condition I should choose and how to apply a potential to one
of the corners.
Since the sheet is suspended in air I thought of putting isolating
boundary conditions on all 4 sides, but then how will I apply the
potential to the corner? Somehow it does not give meaningful results.

Your help is greatly appreciated.

David
 
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I don't know COMSOL so I can't help with your numerical simulation. I can tell you that the potential becomes singular at the infinitesimal points where your are introducing/removing current. Suggest using finite-sized electrodes to make the numerical solver better behaved. A small circular electrode on the plate and a semi-circular electrode at the corner, both small compared to the rectangle but enclosing multiple meshes, should do it.
 
you should be able to set the potential along the boundaries. Make sure youve got a ground somewhere on ther, and have you tried a point condition?
 
@Marcusl: Thanks for the suggestion. makes sense to me.

@Nick: Yes, it is possible to set the potential along a boundary. I could for example define a small square electrode whose boundary I set to a potential of say 5V. I am also able to set the border of the big rectangle to isolating. Now I still need to get a ground somewhere, but where. I think if I want to calculate the resistance between one corner and a point (X,Y) then I have to set the corner to 5V and this point (X,Y) to ground and then somehow calculate the current. But this calculation I would have to code in a script and repeat 10000 times, if I assume a 100 x 100 grid.
I am wondering if there is a faster solution.
I have looked through all Femlab examples and could not find the solution.

Thanks
 
Try and contact Mina with Comsol on their website. she's a big help.
 

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