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Homework Help: Uniform Charge, Electric Field

  1. Jun 21, 2009 #1
    1. The problem statement, all variables and given/known data

    A very long uniform line of charge has charge per unit length 5.38 micro coulombs /m and lies along the x-axis. A second long uniform line of charge has charge per unit length -3.66 micro coulombs /m and is parallel to the x-axis at y = 0.400m. What is the net magnitude of the electric field at the point y = 0.200m? Give your answer in N/C in scientific notation to three significant digits.

    2. Relevant equations

    E=1/2pi(Epsilon)*[Uniform Charge length/R^2]

    3. The attempt at a solution
    I tried summing the two electric fields by using the above equation for each uniform charge and adding them together, however the answer is wrong. I also used 1/4pi(epsilon) but it was still wrong, what am i missing?
  2. jcsd
  3. Jun 21, 2009 #2


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    Homework Helper

    Keep i mind that the E-field is a vector field.

    Add like a vector instead of just summing, because direction matters.

    In this case since they are opposite signs, and your point is in the middle, your answer should be ...

    |E| = |E1| + |E2|
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