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Homework Help: Electron accelerated through a potential difference of 26000

  1. Mar 20, 2012 #1
    1. The problem statement, all variables and given/known data
    An electron is accelerated from rest through a potential difference of 26000 V, which exists between plates P1 and P2, shown below. The electron then passes through a small opening into a magnetic field of uniform field strength, B. As indicated, the magnetic field is directed into the page.
    2. Relevant equations

    3. The attempt at a solution
    I've tried various ways of solving for velocity, but i always come to an equation where i am missing a variable. i tried finding the work so i could divide by the distance to get the force , but i was not given distance.

    Attached Files:

  2. jcsd
  3. Mar 20, 2012 #2
    I had a very similar problem in my physics class, but it turns out there was just an equation that I was unaware of, namely U=qV where U is potential energy, q is a point charge, and V is the potential difference.
  4. Mar 20, 2012 #3
    Well, when the electron is accelerated through two plates with a potential difference of 26000V, the electron has lost 26000V of electric potential. What does this tell you about the electric potential energy of the electron at the moment it exits the plates? In turn, what does that tell you about the kinetic energy of the electron at that point? That should get you on the right rack for finding the velocity.
  5. Mar 20, 2012 #4
    thank you so much man, cant believe i didn't think of that. its so obvious now.
  6. Mar 20, 2012 #5
    No problem. :smile: If you need some help analyzing its motion, when it enters the magnetic field, just post again. :wink:
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