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Ambiguous Electric-Field magnitude

  1. Feb 11, 2014 #1
    1. The problem statement, all variables and given/known data
    On the x axis, charge +Q lies at x = -a and charge -Q lies at x = +a. Point P lies on the axis at
    x = +b, where b > a. a) Work out the electric field magnitude of P b) What is the direction of this …field?

    2. Relevant equations

    3. The attempt at a solution
    E=2kQa/(b2-a2) + 2kQa/(b2-a2)=
    Ep=4kQab/(b^2 - a^2)^2. My teacher said that the solution was correct, however my work was not.
    For b, I determined the direction to be to the right towards the negative charge.

    I would appreciate any assistance.
  2. jcsd
  3. Feb 11, 2014 #2


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    Homework Helper

    The equation in red does not make sense. What are a2, b2? Do you mean that the contribution is the same from both charges?

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