How do you calculate the voltage between two charged nodes?

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Discussion Overview

The discussion revolves around calculating the voltage between two charged nodes in a vacuum, focusing on the concepts of electric potential energy and electric fields. Participants explore various methods and considerations for determining voltage and electric fields in different scenarios, including the influence of charge distribution and the dimensionality of the space involved.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants suggest that voltage can be calculated by knowing the vertex and individual charge of each node and understanding voltage as the difference in electric potential energy.
  • There is confusion regarding the specifics of the nodes and the context of the vacuum, with some participants seeking clarification on the original question.
  • One participant proposes calculating the electric field everywhere as a means to determine voltage, suggesting integration from one surface to another.
  • Another participant mentions that if the objects are not too close, the approximation of the electric field as the sum of the fields of two point charges is reasonable, but complications arise when they are close due to charge distribution influences.
  • Participants discuss the concept of an electric field matrix, with one clarifying that it is actually a vector field and suggesting approximations based on charge distribution shapes.
  • A formula for calculating the electric field in two and three dimensions is provided, emphasizing the importance of charge size for well-defined potential.

Areas of Agreement / Disagreement

Participants express differing levels of understanding regarding the original question and the methods for calculating voltage and electric fields. There is no consensus on a single approach, and multiple competing views remain on how to handle the complexities of charge interactions and field calculations.

Contextual Notes

Limitations include potential misunderstandings of the original question, the need for assumptions about charge distributions, and the complexity introduced by proximity of charged objects affecting each other's distributions.

Cuppasoup
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If:
1) you know the vertex and individual charge of each node and
2) voltage is the difference in electric potential energy between two nodes

How do you calculate the voltage in a vacuum?
 
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Nodes where, vacuum where?
 
mfb said:
Nodes where, vacuum where?
I don't understand your question. 2 objects in space, each with an individual charge(in coulombs). How do you calculate the "tension" (in voltage)between the two charged entities?

By "where" do you mean, "what is the vertex of each node?"? If that's your question, shouldn't it be calculable with a formula?
 
Last edited:
Cuppasoup said:
I don't understand your question. 2 objects in space, each with an individual charge(in coulombs). How do you calculate the "tension" (in voltage)between the two charged entities?
That question is much easier to understand than the original post.
Calculate the electric field everywhere (in most cases, to a good approximation: the sum of the fields of two point charges), integrate from one surface to the other.
 
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mfb said:
That question is much easier to understand than the original post.
Calculate the electric field everywhere (in most cases, to a good approximation: the sum of the fields of two point charges), integrate from one surface to the other.
Okay, thanks for the help! By "Calculate the electric field everywhere," do you mean to calculate 2 individual matrices of "tension" depending on the charge and shape of the object and add them together to calculate the resulting electric field?
 
If the objects are not too close, that will give a reasonable approximation. If they are close, they will influence the charge distribution of the other object and things get complicated.
 
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mfb said:
If they are close, they will influence the charge distribution of the other object and things get complicated.
Oh okay, I guess that means the distinction between "objects" is then blurred.

So how do I calculate an electric field matrix?
 
Cuppasoup said:
I guess that means the distinction between "objects" is then blurred.
Two 1-meter objects with a distance of 0.5 meters between them are clearly different objects, but their charge distributions will influence each other significantly.
Cuppasoup said:
So how do I calculate an electric field matrix?
This is not a matrix, it is a vector field. If you can approximate the charge distribution as spherical, do that. Some other shapes might have analytic solutions, the general case can be treated with numerical methods.
 
mfb said:
This is not a matrix, it is a vector field. If you can approximate the charge distribution as spherical, do that.
Ok, so to start off in 2D with a circle, if I were to calculate a vector field surrounding a charged "point" in the origin, is there a formula to calculate each vector by its coordinate in relation to the charge of the point?
 
  • #10
In a two-dimensional world:
$$\vec E = \frac{q}{4 \pi \epsilon_0} \frac{\vec r}{r^2}$$
In a three-dimensional world:
$$\vec E = \frac{q}{4 \pi \epsilon_0} \frac{\vec r}{|r|^3}$$
Where q is the charge and r is the vector between charge and the point where you calculate the electric field.
Note that the charge should have some finite size, otherwise its potential is not well-defined.
 
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  • #11
Excellent! Thanks!
 

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