1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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

    User Avatar

    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

    User Avatar

    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

    User Avatar

    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

    User Avatar

    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...
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook