# Homework Help: Help interpreting Voltage equation

1. Feb 3, 2010

### EV33

1. The problem statement, all variables and given/known data

Delta V=Delta U/q nat

My question is what exactly is q nat in this equation?

2. Relevant equations

Delta V=Delta U/q nat

3. The attempt at a solution

I am thinking that q nat is the charge at the place where you are trying to find the potential difference. The way my book words it though I am really not sure.

Thank You.

2. Feb 3, 2010

### cepheid

Staff Emeritus
I don't know exactly what that notation means, but the basic idea is that electric potential is potential energy per unit charge. Therefore, if the potential difference between two points in space is $\Delta V$, the total potential energy $\Delta U$ gained or lost by a charge in moving between those two points depends upon the amount of charge that is doing the moving.

3. Feb 3, 2010

### EV33

So if delta U was positive, and q nat was negative then you would get a negative answer? My book says per unit charge also, and I am not sure if that just means magnitude or if it includes the sign also.

4. Feb 3, 2010

### cepheid

Staff Emeritus
If Delta V is positive (i.e. the ending point is at a higher electric potential than the starting point), then a positive charge moving between those two points will gain potential energy, and a negative charge moving between those two points will lose (the same amount of) potential energy. So, yes, the equation includes the sign of the charge.

5. Feb 3, 2010

### EV33

Thank you very much.