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!

Homework Help: Magnetic flux

  1. Dec 13, 2015 #1
    1. The problem statement, all variables and given/known data
    A magnet is used to control negative ions and only allow those with a specific mass to pass through a narrow gap opening . The magnet will bend the ion beam in a quarter circle of radius 50 cm .
    In an experiment, a negative ion accelerated by a voltage of 3.0 kV.

    Which magnetic flux density must the magnets have for these molecules with mass 277 u to follow the circular path through the magnet and get through the gap opening ?

    2. Relevant equations
    QU = MV ^ 2 * 1 / r , then mv ^ 2 * 1 / r = QVB

    3. The attempt at a solution
    Because we have volt , I think QU = MV ^ 2 * 1 / r , then mv ^ 2 * 1 / r = QVB
    But we do not have Q, or v. Thus I do not know how I solve this .

    Sorry for the English, but it seems the problem cant be solved?
  2. jcsd
  3. Dec 13, 2015 #2
    I'm not sure what equation you are using here. What is U?

    You do not need Q to solve this question. You do, however, need v. This v would be the velocity of the negative ions after being accelerated by the voltage of 3kV, right before they enter the magnetic field. Can you find what is this v using the concept of energy?
    Show us your working
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted