# Potential Due to collection of point charges

1. Feb 1, 2005

As shown below, an infinite number of point positive charges of 8.0 C are placed on the x-axis at x=a, 2a, 4a, 8a, ... with a=18 cm. Find the electric potential (in V) at the point x=0.

0---a----2a---4a-----8a-------

Ok so i'm using the equation V=1/(4piEpsilon)Sigma(q/r). and it's not working! I don't understand what i'm doing wrong it should be pretty easy. Please help. I'm using 8 Coulombs as my q and r is my changing variable. I'm getting 88.88 and it's not working.

2. Feb 1, 2005

### vincentchan

your method is fine... what is your answer in term of V,q,a...etc? (not the numerical value )
$$\sum_{x=0}^\infty \frac{1}{2^x} = 2$$

Last edited: Feb 1, 2005
3. Feb 1, 2005

### Pietjuh

Your total potential is just the sum of all the seperate potentials, so:
$$V(0) = \frac{Q}{4\pi\epsilon_0} \sum_{i=0}^\infty \frac{1}{2^i a}$$

Last edited: Feb 1, 2005
4. Feb 1, 2005

### Pietjuh

-blah- stupid

5. Feb 1, 2005

sory, typo