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Homework Help: Make sure electro does not fall!

  1. Jun 18, 2010 #1
    THIS IS NOT A HOME WORK QUESTION THIS AS FROM ANOTHER Tutorial

    find the electric field E need to prevent an electron from falling down to ground, when close to surface of the earth.

    i approached this question saying that take gravity into account and take earth to be negatively charged.

    then Fg=Eq then Fg/q=E..........

    mg/q=E

    is this correct?

    if not can you explain the reasoning plz!
     
  2. jcsd
  3. Jun 18, 2010 #2

    Doc Al

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    Staff: Mentor

    Looks good to me.
     
  4. Jun 18, 2010 #3
    normally do we take earth to be + or negative?
     
  5. Jun 18, 2010 #4

    Doc Al

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    Staff: Mentor

    The electric field surrounding the earth points downward. (The earth is negatively charged.)
     
  6. Jun 18, 2010 #5
    thanks that makes more sense now!
     
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