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Homework Help: Charge to mass ratio

  1. Jan 14, 2010 #1
    electron is deflected in a circular path

    electron speed = 2.7 x 10^8 m/s
    diameter = 3cm
    magnetic field = 0.24T

    1. work out charge to mass ratio - 7.5 x 10^10

    2. the textbook value is 1.76 x 10^11 - comment on this value

    The answer is given as electron travelling close to speed of light so relativistic effects increases mass.

    But increasing the mass will decrease the charge to mass ratio, rather than increase it. Which is what is given by the textbook value...
  2. jcsd
  3. Jan 14, 2010 #2
    What is the question?
  4. Jan 14, 2010 #3
    The textbook value is higher, after taking into account of relatavistic effects, i.e. mass increasing.

    increasing the mass should decrease the value of e/m

    not increase it - which is what has happened there. Why is that?
  5. Jan 14, 2010 #4
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