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Homework Help: Derivation of formula - electrons in an electric field

  1. Jun 28, 2005 #1
    I need to derive the following formula, in relation to the angle between the electron beam and the plates where the beam of electrons hits the plates in a Teltron tube:

    [tex]tan \theta = \frac{Eqs_{h}}{mv_{h} ^2}[/tex]

    I think I managed to complete about 70% of this, but I need to found out what it is in its entirety!
    Last edited: Jun 28, 2005
  2. jcsd
  3. Jun 28, 2005 #2


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    I think we need more information here. Define the variables. Are there both electric and magnetic fields involved in this? Is this something like what you have?

    http://www.telatomic.com/ttubes4.html [Broken]
    Last edited by a moderator: May 2, 2017
  4. Jun 28, 2005 #3
    yeah, that is pretty much the teltron tube i'm referring to. This is only an electric field.

    in the eqn:
    - theta = the angle between the plates (where the stream of electrons hits) and the electron gun (see attached pic)
    - E = size of the electric field between the plates
    - q = charge of the electron
    - s = the horizontal (x) displacement between the electron gun and where the electron stream hits the plates.
    - m = mass of the electron
    - v = horizontal velocity of the electrons in the electron stream

    Attached Files:

  5. Jun 29, 2005 #4


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    Now we can help :smile: Given v and s you can calculate the time of flight, t, through the electric field. From E and q you can calculate the force, F, on the charge. From F and m you can calculate the acceleration, a, toward the positive plate. From a and t you can calculate the velocity component, u, perpendicular to the plate at the moment of impact. [tex] tan \theta [/tex] is the ratio of the two velocity components, u and v.
  6. Jun 29, 2005 #5
    Thanks Dan :smile:
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