Voltage difference = Infinity?

Click For Summary
SUMMARY

The discussion centers on calculating voltage differences between point charges, specifically a Q Coulomb point charge and a -Q Coulomb point charge. The user initially attempts to use the formula V = kq/r + kq/r, mistakenly applying concepts from capacitors to batteries. It is clarified that batteries generate voltage through chemical reactions, not through the principles governing capacitors or point charges. The correct approach for calculating voltage for point charges is confirmed to be V = kq/r, while emphasizing that batteries operate differently from capacitors.

PREREQUISITES
  • Understanding of Coulomb's Law and electric potential
  • Familiarity with the concept of point charges
  • Basic knowledge of electrochemical cells and battery operation
  • Mathematics involving limits and asymptotic behavior
NEXT STEPS
  • Study the principles of Coulomb's Law and its application to point charges
  • Learn about the differences between batteries and capacitors
  • Research electrochemical cells and how they generate voltage
  • Explore the mathematical treatment of electric potential and limits in physics
USEFUL FOR

Students of physics, electrical engineers, and anyone interested in understanding the principles of voltage generation in batteries versus capacitors.

lluke9
Messages
27
Reaction score
0
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...
 
Physics news on Phys.org


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
 

Similar threads

Undergrad Potential difference between a battery's terminal and Earth ground
  • · Replies 58 ·
2
Replies
58
Views
5K
Undergrad Electric Potential in circuit
  • · Replies 3 ·
Replies
3
Views
1K
Undergrad How is Potential Difference Created across a Resistor?
  • · Replies 21 ·
Replies
21
Views
4K
Undergrad Electric Potential -- Is my understanding correct?
  • · Replies 6 ·
Replies
6
Views
1K
Undergrad Physics domain analysis of Voltage drop in series resistor
  • · Replies 7 ·
Replies
7
Views
2K
Undergrad Confused about work done on charge
  • · Replies 8 ·
Replies
8
Views
2K
Undergrad Work to move a point charge from infinity to the centre of a charge distribution
  • · Replies 4 ·
Replies
4
Views
2K
Undergrad Griffith, Electrodynamics, 4th Edition, Example 4.8. (Second part)
  • · Replies 3 ·
Replies
3
Views
547
Undergrad What does it mean to say a battery is however many volts?
  • · Replies 7 ·
Replies
7
Views
2K
Undergrad Understanding the Phase Difference Between Voltage & Current in a Circuit
  • · Replies 7 ·
Replies
7
Views
2K