Potential Due to collection of point charges

[GingerBread27]

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.

 

[vincentchan]

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

 

[Pietjuh]

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

Now try to evaluate this sum and you'll get your answer

 

[Pietjuh]

-blah- stupid

 

[vincentchan]

sory, typo
please don't give out the answer...
leave some work for the OP to do