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Electric Fields Problem

  1. May 19, 2009 #1
    1. The problem statement, all variables and given/known data
    An electron is accelerated from the filament in a vacuum tube towards a metal grid which is maintained at a potential of 180 Volts. It goes through one of the holes in the grid and continues towards a metal plate 1.2 cm away which is maintained at a potential of -10.0 Volts.

    How close to the plate does the electron get?


    2. Relevant equations

    Im not sure, maybe something to do with Potential Difference

    3. The attempt at a solution

    I dont know where to start
     
  2. jcsd
  3. May 19, 2009 #2

    tiny-tim

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    Welcome to PF!

    Hi rhettfraser! Welcome to PF! :smile:

    Hint: work done = ∫ force"dot"distance = ∫ electric-field"dot"charge, and the electron will stop when the KE is zero. :wink:
     
  4. May 19, 2009 #3
    Re: Welcome to PF!

    thanks
     
  5. May 19, 2009 #4
    Re: Welcome to PF!

    but how do you find the force?
     
  6. May 19, 2009 #5

    tiny-tim

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    uhh? you don't, you use ∫ electric-field"dot"charge :smile:
     
  7. May 19, 2009 #6
    ok now ive worked out that the work done is 3.04x10-17
    how should i work out that when KE is zero the electron will stop?
    I know that W= Change in PE, is there anyway that W is related to KE?
     
  8. May 19, 2009 #7

    tiny-tim

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    Conservation of energy … KE + PE = constant :smile:

    (or work-energy theorem …KE + W = constant)
     
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