COMSOL is not considering the relative permittivity

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I am using the guide for capacitors and resistors and i can see that COMSOL is not taking the proper values. If I manually multiply the equation while plotting it matches to what graphs i should get and if I place a dielectric in some other medium there is no variation in field or potential


3 Replies Last Post May 20, 2025, 8:53 a.m. EDT
Jeff Hiller COMSOL Employee

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Posted: 1 day ago May 19, 2025, 9:03 a.m. EDT

Hello Vikash,

You may be considering one of those (many) situations where some of the fields are independent of some of the material properties. See this old thread for a discussion of that.

Best,

Jeff

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Jeff Hiller
Hello Vikash, You may be considering one of those (many) situations where some of the fields are independent of some of the material properties. See [this old thread](https://www.comsol.com/forum/thread/160711/changing-material-does-not-change-electric-field-distribution?last=2017-11-27T15:17:00Z) for a discussion of that. Best, Jeff

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Posted: 12 hours ago May 20, 2025, 6:38 a.m. EDT
Updated: 12 hours ago May 20, 2025, 6:40 a.m. EDT

i am trying to find the electric potential and capacitance, should it not depend on the material and the video i followed (https://www.comsol.com/support/learning-center/article/introduction-to-modeling-resistive-and-capacitive-devices-27591/132) had different results with different materials, i tried multiple time to make sure i followed all the steps. The results from the video and mine varied in the way that if nylon had been used i would get a value of capacitance 4 times lesser, which is the relative permittivity of nylon

i am trying to find the electric potential and capacitance, should it not depend on the material and the video i followed (https://www.comsol.com/support/learning-center/article/introduction-to-modeling-resistive-and-capacitive-devices-27591/132) had different results with different materials, i tried multiple time to make sure i followed all the steps. The results from the video and mine varied in the way that if nylon had been used i would get a value of capacitance 4 times lesser, which is the relative permittivity of nylon

Walter Frei COMSOL Employee

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Posted: 10 hours ago May 20, 2025, 8:53 a.m. EDT

Hello Vikash,

As of more recent versions of the software (since those tutorials were published) the Electrostatics interface now has a "Free Space" feature that imposes unit permittivity on all domains. Override this with the "Charge Conservation in Solids" feature.

Hello Vikash, As of more recent versions of the software (since those tutorials were published) the Electrostatics interface now has a "Free Space" feature that imposes unit permittivity on all domains. Override this with the "Charge Conservation in Solids" feature.

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