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Homework Help: Magnetic Moment

  1. Aug 13, 2009 #1
    1. The problem statement, all variables and given/known data

    find the magnetic moment of a hydrogen atom given that the election moves at 0.10c around the nucleus and the radius is 0.5*10^-5 m

    2. Relevant equations


    3. The attempt at a solution

    this is what i did.

    I = nev
    =ev (I = current e= charge of electron, v = velocity)

    m = IA (A = area)

    my result is 12 A m^2.

    The result looks too big...am I doing something wrong. can you please verify that my answer is right.
  2. jcsd
  3. Aug 13, 2009 #2

    Doc Al

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    Staff: Mentor

    What's n?

    Hint: Find the current by figuring out long it takes for the electron to orbit the nucleus.
  4. Aug 13, 2009 #3
    Your approach is correct, you may want to check your units.

    e = 1.6*10^-19 coulomb
    v = 3*10^7 m/s
    r = 0.5*10^-5 m

    I = q v
    m = I pi r^2

    I get:

    I = 4.8*10^-12
    m = 3.77*10^-22
  5. Aug 13, 2009 #4

    Doc Al

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    Staff: Mentor

    You might want to rethink that equation.
  6. Aug 13, 2009 #5

    hi sorry about that i made a typo.
    n=number of free electron

    and I = nev/(r*pi*r) (r= radius of atom)

    the answer i got before is still correct. I just made a typo while putting the detials in the computer.

    I am just suprised that the magnetic moment for an atom is so high. CAn you please verify the answer. or tell me if i have made any other mistake.
  7. Aug 13, 2009 #6

    Doc Al

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    Staff: Mentor

    OK, so n = 1.

    That doesn't look right. (Check the units.)
  8. Aug 14, 2009 #7
    I = ev/2*pi*r

    it should be right now.
  9. Aug 14, 2009 #8

    Doc Al

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    Staff: Mentor

    Now you've got it.
  10. Aug 14, 2009 #9
    Oops, I forgot to normalize by the distance. You are right.

    It should be

    I = q v / (2 pi r)
  11. Aug 14, 2009 #10

    thabk you all for you help...
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