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Homework Help: Bainbridege mass spectrometer

  1. Mar 12, 2006 #1
    The electric field between the plates of the velocity selector in a Bainbridege mass spectrometer is 20 V/m, and the magnectic field in both regions is 10 T(out and inside the spectrometer). A stream of singly charged selenium ions moves in a circular path with a radius of 1 m in the magnectic field(after they come out from the spectrometer). Determine the mass of one selenium ion.

    How do I get the mass when I don't know the charge?
    I know that v=E/B and Forces equal but I just can't find M without knowing the charge.
  2. jcsd
  3. Mar 12, 2006 #2


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    Unless it means something else, a "singly charged" ion means that an electron has been removed from the selenium atom valence shell. So yes, you do know the amount of charge on the ions.

  4. Mar 12, 2006 #3
    I think I need to polish my english reading ability!
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