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Homework Help: Potential Due to collection of point charges

  1. Feb 1, 2005 #1
    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.


    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. jcsd
  3. Feb 1, 2005 #2
    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
    [tex] \sum_{x=0}^\infty \frac{1}{2^x} = 2 [/tex]
    Last edited: Feb 1, 2005
  4. Feb 1, 2005 #3
    Your total potential is just the sum of all the seperate potentials, so:
    [tex]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 :rolleyes:
    Last edited: Feb 1, 2005
  5. Feb 1, 2005 #4
    -blah- stupid
  6. Feb 1, 2005 #5
    sory, typo
    please don't give out the answer.....
    leave some work for the OP to do
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