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Relative Permittivity has no effect?

Posted Mar 13, 2012, 10:13 p.m. EDT 3 Replies

Christopher Scott
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How come I see no change in the electric field when changing the relative permittivity of the material between and surrounding the parallel plate capacitor in the attached example?

Thanks

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3 Replies Last Post Mar 14, 2012, 2:28 p.m. EDT
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Mar 14, 2012, 2:41 a.m. EDT
Hi

because the electrioc field will not change, the capacitance yes (and it does, try to give er=1000 and solve and integrate your capacity variable

You need to add a second material in between the electrodes and change one of the two Er to see any true change in electric fields

--
Good luck
Ivar
Hi because the electrioc field will not change, the capacitance yes (and it does, try to give er=1000 and solve and integrate your capacity variable You need to add a second material in between the electrodes and change one of the two Er to see any true change in electric fields -- Good luck Ivar
Christopher Scott
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Posted: 1 decade ago Mar 14, 2012, 11:19 a.m. EDT
So are you saying that Comsol isn't giving me the Eeffective = E-Epolarization but only E, where Epolarization is due to the dielectric?

Thanks
So are you saying that Comsol isn't giving me the Eeffective = E-Epolarization but only E, where Epolarization is due to the dielectric? Thanks
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Mar 14, 2012, 2:28 p.m. EDT
Hi

you are right, I was a bit too quick, there I you look at "V" the way you have made your model. There you will not see any rainbow color change for V with er=1 or er = 1000 for the air.

But if you look at D or E (vector components), you will notice a difference in your model by changing the er of air, there we agree and COMSOL is calculating correctly ;)

If you add a domain in part of the air gap height and change the "er" of this domain, then you will also notice the change in the V value in the gap

--
Good luck
Ivar
Hi you are right, I was a bit too quick, there I you look at "V" the way you have made your model. There you will not see any rainbow color change for V with er=1 or er = 1000 for the air. But if you look at D or E (vector components), you will notice a difference in your model by changing the er of air, there we agree and COMSOL is calculating correctly ;) If you add a domain in part of the air gap height and change the "er" of this domain, then you will also notice the change in the V value in the gap -- Good luck Ivar

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