# What is the potential difference between the plates?

1. Feb 6, 2004

### eku_girl83

Here's my problem:
A parallel-plate air capacitor has a capacitance of 730 picoFarads. The charge on each plate is 2.95 microCoulombs.
a) What is the potential difference between the plates? I used the equation V=Q/C to get 2.4746E-4 V, but this is incorrect.
b)If the charge is kept constant, what will be the potential difference between the plates if the separation is tripled?
I think it would be divided by three.
c) How much work is required to triple the separation?
U=1/2 Q V

I think if I could calculate the potential difference correctly, I could work the rest of the problem. Any hints/help would be welcome!!!

2. Feb 6, 2004

### Integral

Staff Emeritus
Check your arithmetic, I do not get the result you posted using the same equation and numbers. Post your calculation.

3. Feb 7, 2004

### eku_girl83

I punched the numbers into the calculator wrong! I now get the voltage equal to 4041.1
Tripling the distance produces a voltage of 3V or 12123.3
Now, how do I apply the equation U=1/2 Q V to find the work required to triple the separation?

4. Feb 7, 2004

### himanshu121

it would be Uf-Ui=W

5. Feb 7, 2004

### eku_girl83

Thank you!!! You are all so helpful :)