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Electric Field question - Why is this answer negative

  1. May 20, 2016 #1
    upload_2016-5-20_18-3-37.png
    upload_2016-5-20_18-3-50.png

    Hello. The first image is the question, the second image is from the solutions manual. I don't understand why these answers are negative. Anyone have a clue?
     
  2. jcsd
  3. May 20, 2016 #2

    berkeman

    User Avatar

    Staff: Mentor

    Sure. (and Welcome to the PF)

    Electric field points from positive charges to negative charges. So the E-field at the first negative charge is pointing inward to that negative charge in all directions. The E-field at the positive charge is pointing away from it in all directions. They ask for the sum of the two E-fields at a point between them, so both components point to the left, which is the negative direction on the horizontal axis.

    Does that help? :smile:
     
  4. May 20, 2016 #3
    Seems reasonable enough, and I feel much better now. Thanks!
     
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