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Electric Field and Equipotential Line Distribution Problem
Posted 11 mar 2020, 16:42 GMT-4 5 Replies
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Hello! I am a new user to COMSOL. Can anyone help me please?
I wanted to generate equipotential lines distribution between 2 parallel metal plates that have a needle like structure attached to one of the plates (attached to plate with zero bias in my case). I want to to vary the length of that needle and simulate equipotential lines in all cases. When the needle length reaches midway between the plates, I get desired equipotential lines but on further increasing the length, I get incorrect distrbution of equipotential lines (kindly refer to the attached images). Since the needle is at zero bias all the time then the equipotential line closest to needle should always be the zero bias one (deep blue color in attached figure) and accordingly rest of the lines should get crowded near the end of the needle (moving from deep blue to red colored line) but what i am getting is, high bias lines cutting the needle plane and not getting crowded which is conceptually incorrect. Can somoeone please tell what mistake I am making in the simulation and how to rectify it to get the desired plot. I am using COMSOL Multiphysics 5.1 version.
Thanks in anticipation!
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Yes, that sure doesn't look right.
1. Take a close look at your boundary conditions, especially on the needle!
2. You didn't show the mesh. If it is fairly coarse, and depending on the smoothing used in the plot, that could also be a problem. So if your boundary conditions are correct, take a look at the mesh. Your mesh size near the needle should be much smaller than the needle size. Note that given the size of the rest of your geometry, if you naively used the default mesh setting, then this is almost certainly your problem! You need to specify a fine enough mesh in the vicinity of the needle.
Scientific Applications & Research Associates (SARA) Inc.
www.comsol.com/partners-consultants/certified-consultants/sara
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Hello Robert,
Thanks a lot for your suggestion. I tried changing the mesh settings and I am getting the desired output now. Thank you so much for the help.
My next step in the problem is to evaluate the electric field contour when some positively charged particles are suspended within metal plates. Can you please guide me which reference model/example I can follow to start this simulation?
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You can define a spatial charge density, if you want. Look around in the interface and you'll find the setting for it. :) Now, if you want to do dynamic simulations of particle motion, that's another/different problem.
-------------------Scientific Applications & Research Associates (SARA) Inc.
www.comsol.com/partners-consultants/certified-consultants/sara
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Dear Robert, I actually want to evaluate the potential field line distribution when positively charged metallic spheres are suspended within metal plates (stationary charge problem). I tried assigning positive charge to metal spheres but the potential distribution afterwards don't look correct. So, can you please suggest an alternative or tell me what mistake I am making in my current approach?
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I suggest that you upload your model to the forum so that anyone interested in it can see how you have configured it and can offer suggestions.
-------------------Scientific Applications & Research Associates (SARA) Inc.
www.comsol.com/partners-consultants/certified-consultants/sara