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How do electrical charges attract/repel each other

  1. Sep 21, 2013 #1
    Ok. I understand like repel and opposite attract. There are these physics homework with 3 charges and find the force from 2 of them on one. I understand the math: the only problem is my signs are wrong due to not understanding the direction of the force.

    For example,
    There's a positive charge (A) on origin. There's a positive charge (B) 4 meters up. There's a neg charge (C) 3 meters x axis and 4 meters y axis. Find the resultant vector on charge 3?

    For me, I would make charge 3 my main object. It would then attract and pull Charge B, making a vector to the SOutheast. It would then pull charge A to the NE direction. Then the resultant vector would be to right. But I am wrong.


    I am literally confused. I do not know which direction to draw the vectors pointing. Please help. Thank you in advance.
     
  2. jcsd
  3. Sep 21, 2013 #2

    Drakkith

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    Staff: Mentor

    If you're trying to find the vector of charge C, then you need to find out which direction the other 2 charges are pulling on it, not which way charge C is pulling the other two.
     
  4. Sep 21, 2013 #3
    So the resultant is to the left?
     
  5. Sep 21, 2013 #4

    Drakkith

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    Staff: Mentor

    If opposite charges attract, then charge C is attracted towards charge B, correct?
    And it also is attracted towards charge A.
    Since both A and B are to the left of C, I'd say that is correct. It should have a vector left and a little down.
     
  6. Sep 21, 2013 #5
    Alright thanks. I think I get it now
     
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