1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Mass spectrometer

  1. Sep 29, 2014 #1
    1. The problem statement, all variables and given/known data
    Consider fields of 1.4e5 N/C and 2.7 T within a velocity selector. If the charge then exits and encounters a field of 1.4 T and radius of 2.4 mm within the mass spectrometer, what would be the mass to charge ratio of this ion?

    2. Relevant equations
    v = E/B
    m = qrB/V

    q = 1.6 x 10 ^-19C
    r = 2.4 x 10^-3 m
    B = 1.4 T

    3. The attempt at a solution

    I got 51851 m/s for v

    and my answer came out way off when I plugged it in for m.

    I have the answer but when I try to do it myself. I get the wrong answer.
    Last edited by a moderator: Sep 29, 2014
  2. jcsd
  3. Sep 29, 2014 #2


    User Avatar
    Science Advisor
    Homework Helper
    2017 Award

    The exercise asks for m/q, not for m. What did you get ?
    And what exactly do you mean when you say 'I get the wrong answer' ?

    By the way: you got 5.2 x 104 m/s, not 51851 m/s : you can't achieve five digit accuracy when all you're given is two digit numbers! But v wasn't wanted.
    (However, when you work out this exercise with the given numbers in the expression for m/q, you do end up to within 1 promille of m/q of a known particle.....what a coincidence!)
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted