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Homework Help: Wild Television Question

  1. Mar 21, 2005 #1
    Hey all, I'm working on this question for my homework. Can someone please help me get it under control, I read it and all I can say is 'huh'?

    In a television picture tube, electrons are accelerated by thousands of volts through a vacuum. If a television set were laid on its back, would electrons be able to move upwards against the force of gravity? What potential difference, acting over a distance of 20 cm, would be needed to balance the downward force of gravity so that the electron would remain stationary? Assume that the electric field is uniform.

    Thanks everyone
  2. jcsd
  3. Mar 21, 2005 #2
    If there is a voltage difference, there must be an electric field. That field is what accelerates particles, and balances gravity (in your question).

    What magnitude electrical field would it take to balance the weight (on earth) of an electron?

    What would the voltage be over a 20cm gap with that electric field?
  4. May 27, 2005 #3
    Ok I think I have the right idea here....


    E = mg/q

    E = V/d

    Now I have values for g, m, d. How do I find q, so I can do the first part of the question?
  5. May 27, 2005 #4


    User Avatar
    Science Advisor
    Homework Helper

    You look in your table of physical constants to find the charge of an electron.
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