Voltage difference = Infinity?

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Discussion Overview

The discussion revolves around calculating the voltage difference between two point charges and the relationship between batteries and capacitors. Participants explore the equations involved in determining voltage and express confusion regarding the appropriate models to use.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant proposes using the equation V = kq/r + kq/r to find the voltage difference between a positive and a negative point charge, expressing concern about division by zero when the distance approaches zero.
  • Another participant questions the appropriateness of using capacitor equations for batteries, noting that they are fundamentally different systems.
  • Some participants express uncertainty about the correct application of voltage equations, with one suggesting that V = kq/r is applicable to point charges while trying to avoid charged spheres for simplicity.
  • A later reply clarifies that a battery generates its voltage through chemical reactions, which contrasts with the electrical principles governing point charges.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the correct approach to calculating voltage differences in this context. There are competing views regarding the relationship between batteries and capacitors, and uncertainty remains about the appropriate equations to use.

Contextual Notes

Some participants acknowledge limitations in their understanding of the mathematics involved and the definitions of the systems being discussed, which may affect their conclusions.

lluke9
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Voltage difference = Infinity?

So if there was a Q Coulomb point charge and a -Q Coulomb point charge with X meters of separation, and I wanted to find the voltage difference between those two charges...
How would I do it?Since V = kq/r + kq/r in this case, wouldn't I have to divide by 0?

V = Qk/X + -Qk/0

Or to avoid the problem, I just made it REALLY close to the charge, like:

V = Qk/X + -Qk/.0000001

Then I'd get some obscenely large number for the voltage for BOTH sides... But I know I'm missing something pretty major here. The potential difference shouldn't be that huge. The reason I want to know is because I'd like to know how to calculate a battery's voltage by knowing just the charges without using capacitor equations.
But I really can't figure this one thing out...
 
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I'm not sure you are using the right equations. First, a battery isn't a capacitor, so why would you use the capacitor equations? The two are very different.

Second, I really don't know the math, so if I'm mistaken I apologize, but googling V = kq/r + kq/r gives me stuff on charged spheres, not point charges. (Edit: Further googling says I'm probably wrong, so just ignore this if it's true)
 


Drakkith said:
I'm not sure you are using the right equations. First, a battery isn't a capacitor, so why would you use the capacitor equations? The two are very different.

Second, I really don't know the math, so if I'm mistaken I apologize, but googling V = kq/r + kq/r gives me stuff on charged spheres, not point charges. (Edit: Further googling says I'm probably wrong, so just ignore this if it's true)

Oh, I assumed a battery was like a capacitor in that it was just two terminals with opposite charges, like capacitor plates. Okay then, scrap that.But yeah, V = kq/r is applicable to point charges.
I wanted to stay away from charged spheres for simplicity's sake.
 


lluke9 said:
Oh, I assumed a battery was like a capacitor in that it was just two terminals with opposite charges, like capacitor plates. Okay then, scrap that.


But yeah, V = kq/r is applicable to point charges.
I wanted to stay away from charged spheres for simplicity's sake.

Nope, a battery generates its voltage from chemical reactions. http://en.wikipedia.org/wiki/Electrochemical_cell
 

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