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How do I find the points where the electric field is zero?

  1. Feb 9, 2017 #1
    1. The problem statement, all variables and given/known data
    Two pairs of charges are shown in Figure 1. Screen Shot 2017-02-09 at 3.08.42 PM.png

    2. Relevant equations


    3. The attempt at a solution
    I originally thought that the electric field past point 7 (i.e. points 8,9, 10) was the solution. However, this is wrong. I then considered point 1, yet that was wrong too. I even considered that there was no point at which the electric field is zero. However, none of these guesses seem to be right. Where am I going wrong in my thinking?
     
  2. jcsd
  3. Feb 9, 2017 #2

    berkeman

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    Staff: Mentor

    Welcome to the PF. :smile:

    What are the magnitudes and signs of the 4 charges shown?
     
  4. Feb 9, 2017 #3
    MasteringPhysics labeled this question as a conceptual question, so no magnitude was given for the charges.
     
  5. Feb 9, 2017 #4

    berkeman

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    Staff: Mentor

    Actually, now that I zoom into the figure, I see the left-hand charges are +4 and the right charge in (a) is +1 and in (b) is -1.

    So I would write Gauss' law for the charge configuration to see where the E-fields from the + and - charges got closest to zero (I agree it will be to the right of the right-hand-charge in (b)...
     
    Last edited: Feb 9, 2017
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