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Homework Help: Electric field from a circle arc

  1. Sep 12, 2012 #1
    1. The problem statement, all variables and given/known data
    Find the x-component of the electric field
    at the origin due to the full arc length
    for a charge of 3.8 μC and a radius of
    1.9 m. The value of the Coulomb constant
    is 8.98755 × 109 N · m2/C2.

    2. Relevant equations
    E = kq/r^2
    dq = q dθ
    λ = Q/ (R θ)

    3. The attempt at a solution
    I said E = kq/r^2
    And so Ex = kq/r2 * sinθ
    and dEx = k*dq/r2 * sinθ
    and dq = λ ds
    ds = R dθ
    λ = q/s
    so dq = Q/θ dθ

    I get kq/r2 ∫sinθ/ θ dθ

    But when I input the answer from this integral (from the calculator) the answer is wrong.

    Attached Files:

  2. jcsd
  3. Sep 12, 2012 #2


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    Homework Helper

    What is your answer?
  4. Sep 12, 2012 #3
    I got 12968.1 N/C.

    Is my method correct?
  5. Sep 12, 2012 #4


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    Homework Helper

    I don't think so.
    dq = λ*ds, where
    λ= q / s , ds = r*dθ and s = πr/2
    Substituute these values in the expression of dE and find the integration taking limits θ = 0 to π/2
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