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Homework Help: Field strength!

  1. Feb 10, 2008 #1
    1. The problem statement, all variables and given/known data

    +1.5x10^-6C, +3.0x10^-6C, 0.20m

    2. Relevant equations

    Two charges of +1.5x10^-6C and +3.0x10^-6C are 0.20m apart. Where is the electric field between them equal to zero?

    3. The attempt at a solution

    = (9.0x10^9)(1.5x10^-6C) + (9.0x10^9)(3.0x10^-6C)
    x^2 (0.2-x)^2
    1.5(0.2-x)^2=3.0(x^2)
    (0.2-x)^2=2(x^2)
    0.4-0.2x-0.2x+x^2=2x^2
    -x^2-0.4+0.04=0

    The answers you'll get are -0.48 and 0.08. The answer in the text is 1.2x10^-1m and you can get it if it's 0.06 instead of 0.04. I looked over my work but I can't find where I went wrong. =(
     
  2. jcsd
  3. Feb 10, 2008 #2

    rock.freak667

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    Homework Helper

    The electric field strength due to Q1(at distance x from Q1)=The electric field strength due to Q2(at the distance of x from Q2)
     
  4. Feb 10, 2008 #3
    Sorry, I don't really understand what you're trying to say. Can someone please tell me which line is incorrect so I can take a closer look and figure it out again.
     
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