# Voltage difference = Infinity?

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...

Drakkith
Staff Emeritus

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)

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.

Drakkith
Staff Emeritus

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