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Electric field and electric force

  1. Jan 19, 2009 #1
    1. The problem statement, all variables and given/known data

    What is the electric field at location of charge q

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    2. Relevant equations



    3. The attempt at a solution

    My intuition in solving this is by finding the field of each charges relative to q and add them all, so for example for the 2q charges relative to q, the electric forces it contributes is ke * 2q/a^2, am I right?
     
  2. jcsd
  3. Jan 19, 2009 #2

    rl.bhat

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    You have to find the magnitude and direction of forces due to three charges at q, and then find the vector sum of all forces.
     
  4. Jan 19, 2009 #3
    That's what I was trying to say, so say the magnitude of the force 2q at q is ke * 2q/a^2 in the positive x direction (or i hat) , am I right?
     
  5. Jan 20, 2009 #4

    rl.bhat

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    Yes. You right. Similarly find the forces due to 3q and 4q, and find the vector sum.
     
  6. Jan 20, 2009 #5
    hmm..for the 3q charge, the distance to q is sqrt(2)a, so therefore the magnitude can be found by:

    ke * 3q/(sqrt(2)a)^2 cos(45) i + ke * 3q/(sqrt(2)a)^2 sin(45) j

    is this correct?
     
  7. Jan 20, 2009 #6

    rl.bhat

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    You can directly wright down as ke*3q/2a^2 for 3q and ke*4q/a^2.
    Field due 2q and 4q are perpendicular to each other. Find the resultant of these fields. Add it to the field due to 3q to get the final field.
     
  8. Jan 20, 2009 #7
    >>Field due 2q and 4q are perpendicular to each other. Find the resultant of these fields.

    Well I already did find the field due 2q and q right? Why do I have to find between 2q and 41? The question asks with respect to q
     
  9. Jan 20, 2009 #8

    rl.bhat

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    The field at location of charge q is the vector sum of fields due to 2q, 3q and 4q.
     
  10. Jan 20, 2009 #9
    Thats trueand so why is my answer 2 posts above is wrong?
     
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