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Homework Help: Electric field and a tv tube

  1. Jan 29, 2005 #1
    electric field

    I can't find any straight forward solutions to this problem.. it's not addressed in the textbook (even though there is a chapter problem about it) and the internet doesn't have what I need either. I'm hoping someone could give me some insight on this.

    An electron (q = -1.602 x 10^-19 C) is projected horizontally into the space between two oppositely charged metal plates. The electric field between the plates is 503.0 N/C, directed up.
    (a) While in the field, what is the force on the electron?

    (b) If the vertical deflection of the electron as it leaves the plates is 3.20 mm, how much has its kinetic energy increased due to the electric field?

    For (a), I found the force to be 8.058E-17N down.

    (b), I think I need to know what the velocity is. I know a few equations but I don't know how to use them for this.
    The equations I know are:
    K = (1/2)mv^2 which I found (on the 'net) to be equal to eV = (1/2)mv^2.
    kinematic equations
    F = ma = qE
    Last edited: Jan 29, 2005
  2. jcsd
  3. Jan 29, 2005 #2


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    Fot the second point,how about considering that the work done by the electric force is equal to the variation of the KE???


    P.S.What "V" are u talking about?
  4. Jan 29, 2005 #3
    Genius! The chapter and my professor didn't mention anything about work (or kinetic energy as it applies to the electric field for that matter).

    Thank you so much :)

    I don't know what that V is.. some webpages I found just used it. When I tried to apply it, I just used the elementary charge e (don't ask me why..)
  5. Jan 29, 2005 #4


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    That probably is the ACCELERATING (ELECTRIC) POTENTIAL DIFFERENCE.In this problem,it's unknown and moreover useless...

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