Multiple electrodes - capacitance.

Click For Summary

Discussion Overview

The discussion revolves around calculating the capacitance between multiple electrodes placed inside a pipe, with a focus on the geometric arrangement of the electrodes and the dielectric properties of the material. Participants explore the implications of the arrangement and the conditions under which capacitance can be determined.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant inquires about finding the capacitance of three electrodes given the voltage of one and the dielectric constant of the material.
  • Another participant emphasizes that the geometric placement of the electrodes is crucial for determining capacitance.
  • A clarification is made that electrodes refer to metal plates and questions arise about their arrangement and spacing.
  • Participants discuss the formula for capacitance (C = e(A/d)) and its applicability when the distance (d) is small compared to the size of the plates.
  • Concerns are raised about the accuracy of the capacitance formula when the distance is not small, suggesting that measurement may be necessary instead.
  • Methods for measuring capacitance are proposed, including using a capacitance meter or measuring discharge time through a resistor.

Areas of Agreement / Disagreement

Participants express differing views on the clarity of the initial problem statement and the implications of the electrode arrangement. There is no consensus on how to calculate capacitance for the described setup, and multiple approaches and considerations are presented.

Contextual Notes

The discussion highlights the importance of geometric factors and the dielectric properties in capacitance calculations, but lacks specific definitions and assumptions regarding the arrangement of the electrodes and the conditions under which the capacitance is being measured.

Dafe
Messages
144
Reaction score
0
Hey,
I have a length of pipe. Inside the pipe walls I have placed four electrodes. If one is giving out
x volts, and I know the dielectric constant of the material between them, is there an easy way of finding the capacitance on the other three electrodes?

I'm looking for hints as well as good resources on the subject.

Thank you.
 
Engineering news on Phys.org
It really depends on the geometric placement.

What's an electrode?
 
By electrodes I mean plates of some metal.

Let's say the plates are facing each other if you know what I mean..
 
Dafe said:
By electrodes I mean plates of some metal.

Let's say the plates are facing each other if you know what I mean..

You're language is hard to follow, but you should elaborate more. Are they stacked like coins with some space in between? What's the spacing.

The "capacitance on them" doesn't mean anything. You might validly ask about the capacitance between two plates (or electrodes). Each plate can have a voltage relative to some other plate. The pipe itself is a "plate".
 
Let's say that the pipe is made of glass.
I make four rectangular shapes of some metal.
I glue them inside the pipe walls.
I have a battery connected to one of the metal shapes.
Can I then find out the capacitance on the other metal shapes?

Is this a better explanation?

Thank you for your patience!
 
C = e(A/d)

For d is small compared to the size of the plate:

C is the capacitance between[i/] two plates.
e is the dialectric constant of the material
A is the area of a plate
d is the distance between them
 
What if d is not small compared to the size of the plates?
 
Then the simple formula Phrak gave is not accurate. You would have to measure the capacitance.

It can be measured with a capacitance meter (some DVM's have that feature). Or measure the time to discharge the cap through a resistor by measuring the capacitor voltage during discharge -- either with a DVM if the discharge time is longer than several seconds, or on an oscilloscope if the discharge time is shorter.

From your description, it sounds like you would a capacitance meter or an oscilloscope -- discharge time should much faster than 1 sec if d is the thickness of a glass pipe.
 

Similar threads

Replies
3
Views
1K
  • · Replies 3 ·
Replies
3
Views
1K
  • · Replies 17 ·
Replies
17
Views
3K
Replies
4
Views
2K
  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 4 ·
Replies
4
Views
4K
  • · Replies 3 ·
Replies
3
Views
3K
  • · Replies 27 ·
Replies
27
Views
7K
  • · Replies 2 ·
Replies
2
Views
4K
Replies
1
Views
2K