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+5 nC converted to # electrons

  1. Feb 9, 2006 #1
    Ok, for some reason, I'm getting the wrong answer. It's asking for how many electrons were removed from an object that has gained a +5nC charge. Here's my setup.

    (1.60x10^(-19)) / ( 5*10^(-9))
    I'm getting 3.2*10^(-11)
    yet book says the answer is actually 3.13*10^(-10)

  2. jcsd
  3. Feb 9, 2006 #2


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    Well both the book and you are wrong.

    If you want wow many electrons are in 5nC, the correct division is 5nC/e. You did e/5nC. The book only has a sign error in the exponent.

    You should have gotten a clue that the book answer was wrong, as 3.13*10^(-10) is less than 1 electron and it is a law of nature that you can only mova around charges in amounts multiple of e (until we find how to separate quarks from hadrons that is).
    Last edited: Feb 9, 2006
  4. Feb 9, 2006 #3


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    Look at your units. Make sure they cancel, as shown below.

    [itex]5\,\textrm{nC} \cdot \frac{1 \,\textrm{electron}}{1.6 \cdot 10^{-19} \,\textrm{C}} = x \, \textrm{electrons}[/itex]

    - Warren
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