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Radius of hellical chain (radius of path of electron)?

  1. Apr 4, 2014 #1
    1. The problem statement, all variables and given/known data

    here's the question, is my concept correct? the ans is 9.86 cm, but my ans is 13 cm, can anyone tell me which part is wrong?

    2. Relevant equations



    3. The attempt at a solution
     

    Attached Files:

  2. jcsd
  3. Apr 5, 2014 #2

    mfb

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    For your formula, you have to take the perpendicular component of the velocity only.
     
  4. Apr 5, 2014 #3
    perpendicular velocity is v sin tetha, so i sub all the values to the working above, i would get r=(mv)/(Bq sin 60) , where m=9.1x10^-31 , v= 4.0x10^7 ms^-1 B=2.0x10^-3 T , q=1.6X10^-9C , i would get 0.13m but not 9.86 cm.... what's wrong with my working?
     
  5. Apr 6, 2014 #4

    mfb

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    At one side you did use the angle, but I think at the other side you did not.
     
  6. Apr 7, 2014 #5
    what do u mean? can you expalin more detail?
     
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