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Electric field question help. Fairly simple but think I'm making small mistakes

  1. Feb 7, 2010 #1
    1. The problem statement, all variables and given/known data

    The electric field at the point x=5.00 cm and y=0 points in the positive x direction with a magnitude of 10.0 N/C. At the point x=10.0 cm and y=0, the electric field points in the positive x direction with a magnitude of 15.0 N/C. Assuming the field is produced by a single point charge, find (a) it's location and (b) the sign and magnitude of its charge

    2. Relevant equations
    E= kq/r^2


    3. The attempt at a solution

    1.5E1=E2

    1.5 kq / x^2 = kq/ (x-5)^2

    1.5(x-5)^2 = x^2

    used quadratic, got x=27.2 , assumed charge is positive because E field strength increases as you move in the positive x direction.
    BUT I think my reasoning might be wrong..
     
  2. jcsd
  3. Feb 8, 2010 #2

    gabbagabbahey

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    Hi KatherineK, welcome to PF!:smile:

    You might be confusing yourself with this notation; what does the "x" in this equation represent?

    Are you assuming that the charge is located along the x-axis (y=0)? If so, what is your reasoning to support this assumption?
     
  4. Feb 8, 2010 #3
    I was making x the distance the charge is from the first electric field (10 N /C)
    and yes, I am assuming the charge is on the x axis
     
  5. Feb 8, 2010 #4

    gabbagabbahey

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    You should probably use a different variable then, so whoever is marking your assignment doesn't think that you are using it to represent the x-coordinate of the point charge.

    Okay, but why?... If you want full credit for your solutions, you should always support any assumptions you make with reasonable arguments.
     
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