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Homework Help: Horizontal component of an electric field at origin

  1. Sep 1, 2013 #1
    1. The problem statement, all variables and given/known data
    Calculating the horizontal component of an electric field at the origin of a semi circle. The image link is: http://imgur.com/SXYs4Rp

    3. The attempt at a solution

    I've tried using the formula k∏(Q)/r (8.98755*10^9)∏(-7.85*10^-6) / .113 = -1.961 * 10^6.
    Can anyone see what I am doing wrong?
  2. jcsd
  3. Sep 1, 2013 #2


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    2017 Award

    Staff: Mentor

    Where does your formula come from? It looks like a wrong application of the formula for a point-charge. Certainly your charge is not a point.
    How did you get r? This is not the same as the length of the semi-circle.
  4. Sep 1, 2013 #3
    The formula was from an example in the book where they used the length of the curve as r but I am guessing I have the wrong formula.
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