Capacitance of an asymmetrical parallel plate capacitor

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Discussion Overview

The discussion revolves around the capacitance of an asymmetrical parallel plate capacitor, specifically when one plate is significantly larger than the other. Participants explore theoretical and practical aspects of calculating capacitance in this scenario, including numerical methods and edge effects.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant inquires about the capacitance between a 1" diameter plate and a 4" diameter plate, expressing difficulty in finding an answer.
  • Another participant suggests that as a first approximation, the capacitance would be similar to that of two identical plates, noting that most electric field lines are perpendicular to the plates.
  • There is a mention that accounting for edge effects complicates the calculation, potentially requiring numerical methods for a more accurate solution.
  • A later post reiterates the initial question about capacitance and suggests that if the plates are sufficiently close, the capacitance would be nearly equivalent to that of two 1" diameter plates.
  • One participant raises the challenge of establishing outer bounds for the electric field in a numerical solution, referencing a hyperphysics example of a spherical capacitor as a potential approach.

Areas of Agreement / Disagreement

Participants express differing views on how to approach the calculation of capacitance, with no consensus on a definitive method or solution. The discussion remains unresolved regarding the specifics of numerical solutions and the impact of edge effects.

Contextual Notes

Limitations include the complexity of edge effects, the need for numerical solutions, and the assumptions made in approximating capacitance based on plate size and distance.

nickexists
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I've been looking all over and to my great surprise have not be able to find an answer to this question.

What is the capacitance between to parallel plates if one plate is larger than the other? For example, the capacitance between a 1" diameter plate and a 4" diameter plate.

Thanks.
 
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The math gets quite tricky when you have situation like that. As a first approximation the capacitance would be nearly the same as for two identical plates (since most of the E-field lines will be perpendicular to the plates). However, if you want to take edge effects into account the calculation becomes tricky and in the "real world" you would probably have to solve this numerically.
 
Thanks. I am actually interested in how this works out in the real world, do you know more specifically how I would go about solving this numerically?
 
nickexists said:
What is the capacitance between to parallel plates if one plate is larger than the other? For example, the capacitance between a 1" diameter plate and a 4" diameter plate.
If the plates are close enough, the capacity will be very close to the capacitor of both plates plates being 1" dia
 
A tricky integral over the volume of the E field... i don't know how one would establish outer bound.
See hyperphysics example of a spherical capacitor , for an approach...
 

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