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Resistivity and Ohm's Law question

  1. Jul 28, 2012 #1
    1. The problem statement, all variables and given/known data
    A long wire connected to the terminals of a 12V battery has 6.4 x 1019 electrons passing a cross section of wire each second. calculate it's resistance.

    answer is 1.2Ω


    2. Relevant equations
    q = ne
    q = IE
    R=ρ L/A


    3. The attempt at a solution
    V= 12v
    n= 6.4 x 1019 electrons
    R=?

    First I used the number of electrons to find my charge (q)
    q = ne
    q = (6.4 x 1019) ( 9 x 10-31)
    q = 5.76 x 10 -11

    Then calculating my current
    I= Q/T
    Im assuming T is 1s, because it says "passing a cross section of wire each second"
    I = 5.76 x 10 -11/ 1
    I= 5.76 x 10 -11

    Then i calculated my resistance
    R= V/R
    R= 12/5.76 x 10 -11
    R= 2.0 x 1011

    What am i doing wrong? D:
     
  2. jcsd
  3. Jul 28, 2012 #2

    rock.freak667

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    The charge of an electron is e=1.6(10-19) C.
     
  4. Jul 28, 2012 #3

    Simon Bridge

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    ... that would be the electron mass.

    e=1.60217646×10-19 Coulombs
     
  5. Jul 28, 2012 #4
    LOL! CRAP! i knew that~ :) Thank you :3 I was going insane for a bit.
     
  6. Jul 29, 2012 #5

    Simon Bridge

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    Happens to the best of us :-)
     
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