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Homework Help: Electron through electric and magnetic field

  1. Nov 4, 2012 #1


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    1. The problem statement, all variables and given/known data

    An electron, initially at rest, is accelerated by a potential V in a vacuum and
    then travels horizontally in a region of space where there is an electric field,
    E, and a magnetic field, B. The fields are aligned such that the electron
    is subjected to a force eE upwards and a force evB downwards, where e
    is the charge of the electron and v is its velocity. If E = 1000 V/m and
    B = 1 × 10^(-5) T, what is the value of the initial accelerating voltage V for
    the electron to continue flying undeflected?
    (Take m=10^(-30) kg and e=1.6×10^(-19) C)

    2. Relevant equations

    No idea.

    3. The attempt at a solution

    No idea.
  2. jcsd
  3. Nov 4, 2012 #2
    some equations for you:

    upward F=qE
    downward F=Bqv

    (travelling straight so upward F=downward F)

    Then, regarding voltage:


    can you find the voltage from these equations?
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