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Homework Help: What is the excess charge on the surface of the earth?

  1. Feb 11, 2008 #1
    1. The problem statement, all variables and given/known data

    The earth has a vertical electric field at the surface, pointing down, that averages 117 N/C. This field is maintained by various atmospheric processes, including lightning. What is the excess charge on the surface of the earth?

    2. Relevant equations

    E=ke*Q/r^2 Q=Er^2/ke

    3. The attempt at a solution

    I attempted to plug in E = 117, r= radius of the earch, and ke= 8.99*10^9 into the equation to find Q, but this answer was wrong. Any ideas, thanks.
  2. jcsd
  3. Feb 12, 2008 #2
    Why don't you use the formula for Electric flux? The Net electric flux through surface is basically Electric field * (4pi*(radius of earth ^ 2)) = excess charge / permittivity constant.
  4. Feb 12, 2008 #3
    Ah..thank you.
    Last edited: Feb 12, 2008
  5. Feb 12, 2008 #4
    Yeah, permittivity constant is 8.85*10^-12.
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