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modeling of electric field

Posted Jul 26, 2012, 8:45 a.m. EDT Electromagnetics Version 4.2 5 Replies

Sam Godric
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Hi,

I made a electric field model with two electrode and single material between them. And the material permittivity

consists of real and imaginary permittivity such as A-i*B.

By applying a sinusoidal voltage on the electrode, the resultant current was supposed to contains both capacitive and

resistive components, so the current was supposed to leading the voltage 0-90 degree.

BUT now it is lagging behind the voltage exactly 90 degree. It seems that the imaginary permittivity of the material

does not influence the resultant current no matter how I change the value.

I am looking for the interpretation of this result.

Thanks.

Sam
5 Replies Last Post Jul 27, 2012, 10:37 a.m. EDT
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Jul 26, 2012, 4:42 p.m. EDT
Hi

could it be you do not use the same sign convention for your complex vaues ?
That would lead to a 180° phase offset, no ?

Check with the doc, as there are several conventions around.


--
Good luck
Ivar
Hi could it be you do not use the same sign convention for your complex vaues ? That would lead to a 180° phase offset, no ? Check with the doc, as there are several conventions around. -- Good luck Ivar
Sam Godric
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Posted: 1 decade ago Jul 27, 2012, 9:19 a.m. EDT
hi Ivar,

sorry I dont understand what you mean. "i" cannot represent imaginary part?

cheers.

Sam
hi Ivar, sorry I dont understand what you mean. "i" cannot represent imaginary part? cheers. Sam
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Jul 27, 2012, 9:42 a.m. EDT
Hi

Sorrry for not being clear, you are right "i" represents sqrt(-1) with COMSOL, but there are often two conventions when representing imaginary material characteristics, the "real + i* imag" and the "real - i*imag" way. I was just woundering if you had checked that you and COMSOl was using the same convention and that you did not have a "-" sign error/difference in the material data, as this would also lead to a 180° phase difference

--
Good luck
Ivar
Hi Sorrry for not being clear, you are right "i" represents sqrt(-1) with COMSOL, but there are often two conventions when representing imaginary material characteristics, the "real + i* imag" and the "real - i*imag" way. I was just woundering if you had checked that you and COMSOl was using the same convention and that you did not have a "-" sign error/difference in the material data, as this would also lead to a 180° phase difference -- Good luck Ivar
Sam Godric
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Posted: 1 decade ago Jul 27, 2012, 10:32 a.m. EDT
hi Ivar,

Thank you!

the current indeed turns to leading the voltage 90 degree after i change the permittivity to -A-i*B.

it makes sense as if i do it by calculation, the results will also turn to opposite value.

but the imaginary part still have no influence on the result.

Regards,

Sam
hi Ivar, Thank you! the current indeed turns to leading the voltage 90 degree after i change the permittivity to -A-i*B. it makes sense as if i do it by calculation, the results will also turn to opposite value. but the imaginary part still have no influence on the result. Regards, Sam
Sam Godric
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Posted: 1 decade ago Jul 27, 2012, 10:37 a.m. EDT
when i insert two different material in the electric field,

the current curve was different from the previous one with single material which one dot represent a current value

become one line as the figure i attached.

but the result when i make the line integration on the gound electrode was one value at one time.

thanks.

Sam
when i insert two different material in the electric field, the current curve was different from the previous one with single material which one dot represent a current value become one line as the figure i attached. but the result when i make the line integration on the gound electrode was one value at one time. thanks. Sam

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