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Homework Help: Find the electric field of a square at a given point?

  1. Jan 26, 2013 #1
    1. The problem statement, all variables and given/known data

    Two tiny objects with equal charges of 6.00uC are placed at the two lower corners of a square with sides of 0.580m.

    When facing the square, Point A is the top left corner. Point B is in the top middle. Point C is dead center inside the square.

    Find the electric field at Point A, the upper left corner.

    2. Relevant equations

    E = K [q1 / d^2]

    3. The attempt at a solution

    Calculated E1 & E2 using above formula and givens, then took the difference to determine the electric field in N/C.
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Jan 26, 2013 #2

    Doc Al

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    Staff: Mentor

    Why did you take the difference? Instead, add the field contribution from each charge, remembering that the field is a vector and must be added as such.
  4. Jan 26, 2013 #3


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    Science Advisor
    Homework Helper

    welcome to pf!

    hi awilliam_3! welcome to pf! :smile:
    (are the charges the same sign, or opposite sign? if they're opposite, then yes, you subtract)

    you can't just add (or subtract) the magnitudes, you have to add (or subtract) the forces as vectors :wink:
  5. Jan 26, 2013 #4
    Ah, I see. Thank you.
  6. Jan 26, 2013 #5
    Re: welcome to pf!

    They are indeed the same sign. Great tip, thank you!
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