# Homework Help: Finding work done when you know electric potential and the charge.

1. Dec 10, 2013

### astru025

Problem:
Points A and B each have an electric potential of +9 V. How much work is required to take 2 mC of charge from A to B?

Equation: V = W / q
9V = W / .002 C
W= .018 J.

This answer I'm getting is incorrect and I'm not sure what else to try. Any help in the right direction would be greatly appreciated! Thanks!

2. Dec 10, 2013

### nasu

What is V in your equation?
The work done between two points depends on the potential difference between the pints.

3. Dec 11, 2013

### astru025

V is voltage. Could you help me a little more on this problem? I'm really stumped on it.,

4. Dec 11, 2013

### haruspex

nasu already told you the important point that you are missing. Potentials are always relative. What matters is the difference in potential. What is the potential difference in this case?

5. Dec 11, 2013

### BeBattey

Voltage = Potential

Same thing, different name.

Note that potential is not potential energy, perhaps this is why we call it voltage instead of something so close to potential energy.

The equation you are citing is missing a delta, that little triangle that denotes 'change in'.

It's actually qΔV = W.