# Electric potential energy and point charges

1. Sep 21, 2009

### cristina045

1. The problem statement, all variables and given/known data
Two point charges , Qz= +5.00 nanoC and Q2= -3.00 nanoC, are separated by 35.00 cm.
a) What is the potential energy of the pair? What is the significance of the algebraic sign?
b) what is electrical potential at a point midway between the charges?
(here i'm supposing i'd do it the same way as in question a but divide the distance in half?)
c)how much work is required to bring a charge Q3=+2.00nanoC from very far away to the point midway between the charges

2. Relevant equations

Im guessing i have to use deltaV=delta PE/q= - Ed but im still not sure about how to proceed because i have coulombs and these equations work in volts.

Also, when it says separated by 35.0 cm, would this equal my height in the potential energy formula?

2. Sep 21, 2009

### mikelepore

There's no height. You're confusing it with gravitational potential energy. Look for a formula for the electrical potential energy for a system of point charges.