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Homework Help: Speed of an Electron and the Magnetic field

  1. Apr 20, 2009 #1
    1. The problem statement, all variables and given/known data

    An electron with kinetic energy 1.60 keV circles in a plane perpendicular to a uniform magnetic field. The orbit radius is 24.0 cm.
    a Find the speed of the electron.
    b Find the Magnetic Field

    2. Relevant equations


    3. The attempt at a solution
    I first converted keV to Joules which came out to be 2.5635 e-16 J

    I then made the equation to solve for v : v=sqrt(1/2mk)

    But I came out with the velocity being e22 4.627 km/s which is not right

    PLease help!!!!
  2. jcsd
  3. Apr 20, 2009 #2


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    Homework Helper

    Hi mlshani,

    This equation does not look right to me; do you see what it needs to be?
  4. Apr 20, 2009 #3
    No I thought that was the equation, at least that is the one on my physics book?
    Is there another equation to find the speed of an electron?
  5. Apr 20, 2009 #4
  6. Apr 20, 2009 #5
    Thank you!

    I can't believe I saw that equation as having everything in the denominator!

    Thank you!
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