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Magnetism Questions Help

  1. Apr 26, 2013 #1
    1. The problem statement, all variables and given/known data
    1. Determine the magnetic force acting on an proton (m = 1.67 x 10-27 kg) moving at 2.9 x 106 m/s in a magnetic field of 6.8 T. The proton is moving south. The magnetic field points straight down.

    2. A 6.0 m long wire with 7.0A of current flowing through it experiences a force of 12 N. Determine the magnitude of the magnetic field. You may assume that the current and the magnetic field are 90° to one another.

    2. Relevant equations
    1. Fm = qvbsinƟ
    2. Fm = IlBsinƟ

    3. The attempt at a solution
    1. There was no charge given so is it alright to use charge of 1.6x10^-19?
    Fm = qvbsinƟ
    Fm = (1.6x10^-19 C)(2.9x10^6 m/s)(6.8T) sin 90
    Fm = 2.53 x 10^-12 N

    2. No magnetic field strength is given so how can i figure out the magnetic field strength?

    Thanks
     
  2. jcsd
  3. Apr 26, 2013 #2
    I would love to know as well...
     
  4. Apr 26, 2013 #3

    rude man

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    Yes. A proton has charge = electron but + instead of -.
    What is the force on a wire of length L in a B field if the B field is orthogonal to the wire? Very basic formula ...
     
  5. Apr 26, 2013 #4
    For number 1 i get: Fm = -3.15x10^-12 N[South]

    For number 2 I am having hard time understanding what you are trying to say.
     
  6. Apr 26, 2013 #5

    rude man

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    If you'll try to answer my question ... I should have added, the wire has a current i flowing thru it.
     
    Last edited: Apr 26, 2013
  7. Apr 26, 2013 #6
    The formula will be F = ILB SinƟ

    This is what I get:
    F = ILB sin 90
    12 N = (7.0 A)(6.0 m)B sin 90
    12 N/(7.0 A)(6.0 m) = B sin 90
    2/7 = B sin 90
    B = 2/7 T
    B = 0.29 T
     
    Last edited: Apr 26, 2013
  8. Apr 26, 2013 #7

    rude man

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    Looking good ...
     
  9. Apr 26, 2013 #8
    Thanks so were those 2 questions correct?
     
  10. Apr 26, 2013 #9

    rude man

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    I did not check your numbers but the formulas were correct.
     
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