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How many electrons make up a charge of -15.0 uC?

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  1. May 3, 2015 #1
    So I've already got some help on this one, now I have a different question pertaining to this equation.

    I know
    N=q/e
    e=-1.6x10^-19
    q=-15x10-6

    so I tried:

    N=(-15x10-6)/-1.6x10^-19
    N=-156/-1.6x10^-19
    N=9.74
    ~that was wrong

    So I thought maybe this:
    N=(-15x10-6)/-1.6x10^-19
    N=--60/-1.6x10^-19
    N=3.8x10^-18
    ~also wrong

    so I thought maybe I need to use the full form of e=-1.602x106-19

    N=(-15x10-6)/-1.602x106-19
    N=-156/-1.602x106-19
    N=9.74x10^-18
    ~that was wrong

    So I thought maybe this:
    N=(-15x10-6)/-1.602x106-19
    N=--60/-1.602x106-19
    N=3.75x10^-18
    ~also wrong

    please help I don't know why it keeps turning up wrong.
     
    Last edited by a moderator: May 4, 2015
  2. jcsd
  3. May 3, 2015 #2

    haruspex

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    Let's start with something simpler.
    What is xa*xb?
    What is xa/xb?
    What is 10-6 / 10-19?
     
  4. May 3, 2015 #3
    what?
     
  5. May 3, 2015 #4

    haruspex

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    I thought my questions were very clear.
    What do you get if you multiply x to the power of a (xa) by x to the power of b (xb)?
     
  6. May 3, 2015 #5
    I think its x^a+b
     
  7. May 3, 2015 #6
    What is x^a*x^b = x^a+b
    What is x^a/x^b = x^a-b
    What is 10^-6 / 10^-19 = 10^-6-(-19) = 10^-25
     
  8. May 3, 2015 #7

    haruspex

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    Close, but you went wrong at the last step. What is -6-(-19)?
    (And you really should use parentheses correctly: x^(a+b) etc.)
     
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