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Charged Particles in Electric and magnetic fields

  1. Sep 4, 2010 #1
    1. The problem statement, all variables and given/known data
    An electron, initially at rest, is accelerated through a potential diff of 15.0 kv. It is then allowed to circulate at right angles to a uniform magnetic field of strength 2.35 T.
    Calculate the electrons final speed before entering the magnetic field.


    2. Relevant equations

    f= eq
    f=bqv

    3. The attempt at a solution

    (15000)q = q(2.35)v
    (15000)= 2.35v
    v= approx. 6383
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
    Last edited: Sep 4, 2010
  2. jcsd
  3. Sep 4, 2010 #2
    Yeah OK so what do you know about this topic?
    If I understand this correctly, the question is what will the speed of the electron be after it has been accelerated by 15kV's, if it started with v = 0.
     
  4. Sep 4, 2010 #3
    I just edited my original post,
    to show how I worked it out before.
     
  5. Sep 4, 2010 #4
    But how does the magnetic field have any significance? Doesn't the question ask the speed BEFORE the electron goes into the magnetic field?
     
  6. Sep 4, 2010 #5
    But won't that leave me with insufficient info?

    because I then have to calculate a with (f=ma), using the f=eq formula.
    But i will require the time that it is in the field to know it's final speed
     
  7. Sep 4, 2010 #6
    All you need to know is the total work done on the electron (W=U*q) and and the work-theory or whatever you call it when dE = W. So this gives you the equation U*q = .5*m*v^2 - 0, where q is the charge of the electron and m is it's mass.
     
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