# Finding the electric potential energy

1. Feb 5, 2012

### sameasabuv

A charge of -2.580 mu C is located at (2.575 m, 4.742 m), and a charge of 1.440 mu C is located at (-2.730 m, 0). Find the electric potential at the origin.

q_1= -2.580*10^-6 C
q_2= 1.440*10^-6 C
k = 8.99*10^9 N*m/C^2
r_2= -2.730 m

V= (k*q_1)/r_1 + (k*q_2)/r_2

So first i found r_1 by using the Pythagorean theorem r_1= √(2.575^2 +4.742^2)= 5.396 m
Then i plugged all the information into the above equation (converting the mu C to C) i came up with the answer -9040 V but it's the wrong answer and i can't figure out what i did wrong.
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Feb 5, 2012

### Spinnor

Check your math. Using your numbers I got a potential of about -4300 V due to the negative charge. The positive charge would only make that number bigger, I can't get your number?

3. Feb 5, 2012

### SammyS

Staff Emeritus
Hello sameasabuv. Welcome to PF!

Don't forget, q1 and q2 have opposite sign.