What if gap is irregular in capacitor

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    Capacitor Gap
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Discussion Overview

The discussion revolves around the theoretical implications of irregular gaps in capacitors, particularly focusing on how voltage is derived in such scenarios. Participants explore the concept of capacitance and voltage distribution in capacitors with non-uniform geometries, touching on both theoretical and practical aspects.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Mathematical reasoning

Main Points Raised

  • One participant expresses uncertainty about voltage concepts and suggests using software to analyze voltage distribution across small segments of an irregular capacitor surface.
  • Another participant proposes that an irregular capacitor can be viewed as multiple capacitors in parallel, where voltage is uniform across an ideal conductor.
  • A different participant mentions the need to calculate total capacitance by summing the capacitances of individual segments, indicating a mathematical approach to the problem.
  • It is noted that the electric field in a capacitor exists between its plates, and the voltage must remain constant along the length of the plates, as long as they are conductive.
  • One participant introduces the idea that deforming the capacitor plates involves work done due to the attractive forces between opposite charges, which can affect the voltage across the capacitor.
  • The relationship between charge, capacitance, and voltage is highlighted, emphasizing that while charge remains constant, changes in capacitance will influence voltage.
  • A reference to an electrometer is made to illustrate the concept of increasing voltage as capacitor plates are separated, suggesting a practical observation related to the discussion.

Areas of Agreement / Disagreement

Participants present various viewpoints and approaches to understanding the implications of irregular gaps in capacitors. There is no clear consensus on the best method to analyze the situation, and multiple competing ideas remain unresolved.

Contextual Notes

Some assumptions about the behavior of electric fields and the uniformity of voltage in conductive materials are present but not fully explored. The discussion also touches on the mathematical relationships involved without resolving specific calculations or definitions.

Who May Find This Useful

Individuals interested in electrical engineering, physics, or those exploring capacitor design and behavior may find the discussion relevant.

Gunmo
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I don't have clear concept on voltage. I am a Mechanical guy.
If the gap is irregular in large capacitor, how voltage is derived in theory. Using software I can divide the surface into many pieces and calculate voltage of individual small piece.

I attached my problem.
 

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Hi Gunmo,

Yes, this is a kind of 'lots of capacities in parallel'.
For an ideal conductor, all the material is at the same voltage: if not, then the potential difference would let the charge carriers move until the potential (voltage) is equal everywhere.
 
So, to find capacitance of the device, I need to divide the area with small element and C = C1 + C2 + C3...
 
The electric field in a capacitor is between its plates.
Since the plates are conductive there can be no field in the direction along their length,
So,
voltage between the plates at any point along their length must be the same, as BvU observed earlier.

But -

That's an interesting example you posed.

Be aware that in deforming the structure work was done while changing the distance between the electrodes.
That's because the opposite charges on the electrodes attract one another.
So when you deformed the plates the Force X Distance product of [ that Coulombic attractive force X distance moved ] has units of work.
That work shows up as a change in voltage across the capacitor.

Charge Q on a capacitor = Capacitance X Voltage
You didn't change Q but you did change Capacitance,
and their ratio is voltage.

Just another little quirk of the universe. Good for "electrical trivial pursuits" parlor games, but don't be surprised if you find it in a physics quiz .

It's good to get your thinking oriented early so that you focus not so much on the plates of a capacitor but on what's in between them.
Watch the electrometer here (about 1:30) indicate increasing voltage as capacitor plates are separated.

 
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