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Homework Help: Electric field symmetry

  1. Dec 16, 2015 #1
    1. The problem statement, all variables and given/known data
    Problem statement:

    In the attached figure, two curved plastic rods, one of charge q and the other of
    charge q, form a circle of radius R 8.50 cm in an xy plane. The x axis passes
    through both of the connecting points, and the charge is distributed uniformly on
    both rods. If q 15.0 pC, what are the (a) magnitude and (b) direction (relative to
    the positive direction of the x axis) of the electric field produced at P, the center of the circle?
    2. Relevant equations
    3. The attempt at a solution

    Read solution on Chegg.com
    My question:
    Why is it that the electric field only have a component in the x-axis?

    Attached Files:

    • spg.png
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  2. jcsd
  3. Dec 16, 2015 #2


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    Homework Helper

    I think the question means the angle the net E field makes with the positive x axis (with the unit vector ##\hat{x}##).
  4. Dec 16, 2015 #3
    To get a better picture of the net field draw the electric field vector from a small segment of the curve
    above the axis and the electric field vector from a corresponding segment below the x-axis
  5. Dec 17, 2015 #4
    Thanks #3 - with the drawing i found the reason :)
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