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Homework Help: Mass spectrometer radius of the path

  1. Oct 12, 2004 #1
    Suppose that an ion source in a mass spectrometer produces doubly ionized gold ions (Au2+), each with a mass of 3.27 x 10^-25 kg. The ions are accelerated from rest through a potential difference of 1.40 kV. Then, a 0.600 T magnetic field causes the ions to follow a circular path. Determine the radius of the path.

    i tried to use

    [tex] r = \frac {\sqrt{2mV}}{2q B^2} [/tex]

    i doubled the q because the question says the ions are doubly ionized. is q = 1.6 e -19 still or is it different with gold ions? my answer was 7.95 e -3 but i'm wrong according to my webassign.
  2. jcsd
  3. Oct 13, 2004 #2


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    Science Advisor
    Homework Helper

    Your denominator also belongs under the radical.
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