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Homework Help: Electron and conducting plate

  1. May 22, 2014 #1
    1. The problem statement, all variables and given/known data

    An electron is projected from a distance d and with initial velocity u parallel to a uniformly charged flat conducting plate as shown. It strikes the plate after traveling a distance l along the direction of projection. The surface charge density of the conducting plate is equal to

    Ans :dε0mu2/el

    2. Relevant equations

    3. The attempt at a solution

    Electric field of the conducting plate = σ/ε0

    Force on the electron in y direction = eσ/ε0

    ay = eσ/mε0

    l=ut and d=(1/2)ayt2

    Solving these ,I get σ = 2dε0mu2/el2 ,but this is incorrect.

    I would be grateful if somebody could help me with the problem.

    Attached Files:

  2. jcsd
  3. May 22, 2014 #2


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    Homework Helper

    Hi Tania,
    It looks correct for me, but do not forget the parentheses.

  4. May 22, 2014 #3
    Hello ehild

    Thank you very much :)
  5. May 22, 2014 #4


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    Science Advisor
    Homework Helper
    Gold Member

    Note that the given answer must be wrong since it has the wrong dimensionality.
  6. May 22, 2014 #5
    Okay . Thanks for the input .
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