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capacitance simulation result is different from direct calculation
Posted 27.07.2015, 17:05 GMT-4 Low-Frequency Electromagnetics Version 5.0 1 Reply
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Dear all,
I am using comsol 5.0 to simulate the capacitance and this is the example I begin with:
www.comsol.com/model/computing-capacitance-12689
In the example, the simulated capacitance is 4.343e^-11
However, if you calculate directly it should be:
C=glass_epsilon(r)*epsilon(0)*area/d=4.2*8.854*10^-12*(3.14*0.1*0.1)/0.03=3.892e^11
I am sure this difference is not due to electric leaking to outside because this big error still exists when I try bigger radius.
There is a similar question asked in 2011 and get no answer:
www.comsol.com/community/forums/general/thread/20992/
I am using comsol 5.0 to simulate the capacitance and this is the example I begin with:
www.comsol.com/model/computing-capacitance-12689
In the example, the simulated capacitance is 4.343e^-11
However, if you calculate directly it should be:
C=glass_epsilon(r)*epsilon(0)*area/d=4.2*8.854*10^-12*(3.14*0.1*0.1)/0.03=3.892e^11
I am sure this difference is not due to electric leaking to outside because this big error still exists when I try bigger radius.
There is a similar question asked in 2011 and get no answer:
www.comsol.com/community/forums/general/thread/20992/
1 Reply Last Post 28.07.2015, 09:33 GMT-4
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Posted:
9 years ago
Dear Jiantao Kong,
The difference in capacitance is in fact caused by the edge effect (the electric field "leaking" outside). You can easily verify this by computing the capacitance after removing the outer region (thus eliminating edge effects):
- In the Electrostatics node, remove all domains from the selection except for the domain between the plates (Domain 3),
- verify that the Ground and Terminal features are applied to the correct boundaries,
- compute the study and evaluate the capacitance: the result is 3.8941E-11 F, which is close to the expected value of 3.8943E-11 F.
The difference in capacitance is in fact caused by the edge effect (the electric field "leaking" outside). You can easily verify this by computing the capacitance after removing the outer region (thus eliminating edge effects):
- In the Electrostatics node, remove all domains from the selection except for the domain between the plates (Domain 3),
- verify that the Ground and Terminal features are applied to the correct boundaries,
- compute the study and evaluate the capacitance: the result is 3.8941E-11 F, which is close to the expected value of 3.8943E-11 F.