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Homework Help: Find the charge's location

  1. Feb 17, 2009 #1
    1. The problem statement, all variables and given/known data
    The electric field at the point x=5.0cm and y=0 points in the positive x direction with a magnitude of 10.0N/C. At the point x=10.0cm and y=0, the electric field points in the positive x direction with a magnitude of 16.0 N/C. Assume this electric field is produced by a single point charge.
    Find the charge's location

    2. Relevant equations
    E= kq/r^2

    3. The attempt at a solution
    So my teacher substituted (x-5) for r^2 and got a quadratic equation. I solved for the quadratic but I'm not getting the right answer.
  2. jcsd
  3. Feb 17, 2009 #2


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    Homework Helper

    Using the Coulomb's e field relationship you should be able to directly relate the 2 field values such that

    16*X2 = 10*(X+5)2

    The product of the distance squared times the field = the same thing.

    The one that is further away will have a smaller |E|.
  4. Feb 19, 2009 #3
    I am having the same problem. Yet out of Coulomb's e Field relationship I get the related field values however when I plus in the appropriate X values they are not equal. I agree that one is further away however that does not determine the charges location.

    Thanks much!
  5. Feb 19, 2009 #4


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    Homework Helper

    Welcome to PF.

    Be careful in what X represents. It is the distance along the X axis from 10 cm. So the location of the charge if that's what you are looking for is at 10 + X cm.
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