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Homework Help: Electrons in a uniform electric field.

  1. May 8, 2007 #1
    1. The problem statement, all variables and given/known data

    Basically, I am writing up a practical experiment dealing with Electrons in a uniform electric field (I.e. Using an electron gun).

    There are two parallel plates, one with a positive charge and one with a negative charge. Between these to plates is a grid which allows for easy graphing.

    It can be assumed that the electric field between the plates is uniform. A grid (with lines seperated by 1 cm) is shown. I need to use this information to determine the distance, d, between the plates and to calculate the strength of the uniform electric field, E.

    How do I find out the distance between the 2 parallel plates? (Probably simplistic, it's just that I am doing this experiment based on an experiment video I watched)

    The anode voltage is set to 3,000 volts.
    The graph I got was y=(.0504)(x)^1.763

    2. Relevant equations

    I am assuming this equation is related...

    E = V/d (V is the potential difference between the plates.)
     
  2. jcsd
  3. May 8, 2007 #2
    Theoretically, the equation is y=(a/2/v^2)x^2

    where, a is the acceleration=eE/m
    v is the initial velocity, assumed to be parallel to the plates

    If you substitute all these quantities to above equation then
    y=eE/(2mv^2)x^2

    and while mv^2/2=eV with V is the voltage

    y=(E/4V)x^2

    You do not need the distance between 2 plates.

    Here you got the power of about 1.7<2. Hmm, was the experiment held in vacuum or in some gas?
     
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