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Homework Help: Electric Field

  1. Jan 27, 2010 #1
    1. The problem statement, all variables and given/known data
    A ring with a 15cm radius and with a uniform charge of 20 micro coulombs is in the yz-plane with the origin at its center. What is the force on a -3 micro coulombs charge on the x-axis at x=5cm?


    2. Relevant equations

    E=kQx/(R^2 + x^2)^(3/2)

    F=QE

    3. The attempt at a solution

    I tried to plug in the numbers for the above equations and can't seem to get the right answer. I first solved for E and then multiplied it to Q which is -3*10^(-6) C...correct?
    The answer should be -6.83 N, but I can't seem to figure it out.
     
  2. jcsd
  3. Jan 27, 2010 #2
    I got -6.8 N when I used your numbers. Check your math, check your unit conversions for the distances and charges, and make sure you're using the correct Q for the electric field.
     
  4. Jan 27, 2010 #3
    Ahh...I made a mistake on my calculator. Thanks for the help.
     
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