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22 Jul 2008
Why is capacitance a geometrical property?
We have seen since our school that capacitance is a geometrical property. It depends on the structure of the two electrodes. But why is it so. Can anyone shed some light on it?
28 Jul 2008
It’s because the capacitance between two plates depends on the electric field between them, which is naturally geometry-dependent; you get a different electric field if you have charges in different places.
The dependence on electric field also explains why capacitance changes when you place a dielectric between the plates, because this also alters the electric field as is easily seen from Maxwell’s equations in matter.
Hope this helps,
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Benjamin P Haley
25 Jul 2008
I’m not sure I completely understand your question, but here are some thoughts. Capacitance is a measure of the amount of charge stored in a device, given the electrostatic potential. In the traditional example, a parallel plate capacitor, the amount of charge stored, and thus the capacitance, is directly proportional to the area of the plates. So changes in the geometry affect the area, which in turn changes the capacitance. I hope this is relevant to your question.