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Homework Help: Electric Field of Three Point Charges

  1. Jan 22, 2012 #1
    1. The problem statement, all variables and given/known data

    Three point charges lie along a circle of radius r at angles of 30°, 150°, and 270° as shown in the figure below. Find a symbolic expression for the resultant electric field at the center of the circle.


    2. Relevant equations


    3. The attempt at a solution

    The two positive charges' horizontal components will cancel out, and their vertical components will combine. This is for the two positive charges:


    The negative charge is all in the vertical direction.


    I pulled the -2 from -2q out front.

    Combining them for the total field:



    How does that look?
  2. jcsd
  3. Jan 22, 2012 #2


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    Homework Helper

    Well, "+-" identical "+" does not look nice :tongue2: Indicate the direction of the contribution of the separate charges to the electric field. So the two positive charges contribute with a downward electric field and that of the negative charge is also downward.

    Last edited: Jan 22, 2012
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