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Period and frequency problem

  1. Oct 3, 2015 #1
    1. The problem statement, all variables and given/known data
    Find the period and frequency of the motion of an electron of kinetic energy, E, 34 KeV as is moves in a circular orbit perpendicular to a magnetic field, B, of 0.270 T.

    2. Relevant equations
    For speed, v:

    For charge, q:

    For mass, m:

    For radius, R:

    For frequency, f:

    For period, T:

    3. The attempt at a solution

    We were told to treat this classically, so I computed the radius by solving for the speed with the classical kinetic energy formula, upload_2015-10-3_16-1-33.png , from which I found upload_2015-10-3_15-33-33.png , which gave me R = 2.2 mm, which is the correct radius. I then went on to use the relation upload_2015-10-3_15-42-32.png and this is where things went horribly wrong. I got the answer upload_2015-10-3_15-47-35.png , which seems very reasonable to me. I obtained upload_2015-10-3_15-50-29.png for the frequency, which also seems very reasonable to me. The only problem is, the answers are wrong or at least our homework website (WebAssign) says that those are the wrong answer. Anyone see a mistake I may be making?

    Attached Files:

  2. jcsd
  3. Oct 3, 2015 #2


    User Avatar
    2017 Award

    Staff: Mentor

    Just a rounding issue? 7.56 GHz according to WolframAlpha.
    Looks correct.
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