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Homework Help: Electric field by infinite line of charge

  1. May 16, 2012 #1
    1. The problem statement, all variables and given/known data
    Given an infinitely long line of charge density λ extended along the x-axis, what is the electric field at a point X = x(x')+y(y')+z(z') (in space)?

    2. Relevant equations

    E = kq / r^2, dq = (lamda)dx

    3. The attempt at a solution

    dE = kλ ∫ [x(x')+y(y')+z(z')- x(x')] dx / [(y^2) +(z^2)]^(3/2) (integral from -∞ to +∞)

    I end up getting 0 because -∞ + ∞ equals 0?
    Last edited: May 16, 2012
  2. jcsd
  3. May 16, 2012 #2


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    Welcome to PF!

    Hi Sam99! Welcome to PF! :smile:

    (try using the X2 button just above the Reply box :wink:)
    shouldn't there be an x2 on the bottom also? :redface:
  4. May 17, 2012 #3
    I don't think so because I'm using (x-x')/ |x-x'|^3.
    would that be right?
  5. May 17, 2012 #4


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    yes, but there's still a difference in x, which has to go on the bottom
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