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Homework Help: Basic electricity problem.

  1. Sep 7, 2013 #1
    1. The problem statement, all variables and given/known data

    Given an electric field ε V/m that is constant in the x-direction and a charge +q C located at the origin and free to move in the x-direction. (a) What is the magnitude and direction of the force F acting on q? (b) If q moves under the influence of F a distance d m, how much work is done by F? (c) Assuming the voltage at the origin to be zero, what is the voltage Vd at x = d m, bearing in mind that ε = -dv/dx? (d) How is the loss in electric potential energy related to the work done by F? (e) Assuming the charge has a mass m kg and zero velocity at the origin, show that the KE of the charge at x = d is equal to the loss in electric potential energy.

    2. Relevant equations

    3. The attempt at a solution

    a. F= εNq in the positive direction
    b. W=Fd
    c. I can guess that it's -εx but I don't know how to explain it properly
    d. Equal by conservation of energy.
    e. Not too sure how.

    Thank you in advance.
  2. jcsd
  3. Sep 7, 2013 #2


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    2017 Award

    Staff: Mentor

    a-d: right.
    For (e), I would use energy conservation. Alternatively, calculate the acceleration, and use this to determine the velocity there.

    The question uses an ugly way to deal with units :(.
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