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Homework Help: Electric Fields Question (deflection? :S? and more)

  1. Apr 5, 2009 #1
    1. The problem statement, all variables and given/known data

    An electron enters a parallel plate apparatus 10cm long and 2.0cm wide, moving horizontally at 8.0 x 10^7 m/s.

    If the potential difference acrros the plates is 600V:

    a) the vertical deflection of the electron from its original path.
    b) the velocity with which it leaves the parallel plate apparatus, inboth magnitude and direction.

    2. Relevant equations

    I'm not sure which are relavent. I tried in corporting all motion equations.

    3. The attempt at a solution

    There are so many ways I tried to solve this question

    I already know the answer to it, but it seems impossible to get it.

    and 8x10^7m/s (right5down)

    I dont expect you to solve them all for me (although it would be much helpful) , but please help me start in the right direction.

    Thank you
  2. jcsd
  3. Apr 5, 2009 #2


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    Homework Helper

    First of all find the time taken by the electron to cover 10 cm.
    Find the electric field between the plates. Then force on the electron. Using mass of the electron, find the acceleration of it. Now treat the electron as a projectile,and find the vertical deflection.
  4. Apr 5, 2009 #3
    okay, what do you the electric field?

    the intensity? v/d?
  5. Apr 5, 2009 #4


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    Homework Helper

    Yes. v/d.
    What is F? What is a?
  6. Apr 5, 2009 #5
    okay i got the answer to a) finally! :D

    now b... hm.....
  7. Apr 5, 2009 #6
    how would i start this one.?

    i tried..

  8. Apr 5, 2009 #7


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    Homework Helper

    Initially there is no vertical velocity. SO vi = 0.
    Find the time t taken by the electron to travel 10 cm.
    Find the vertical velocity after t s.
    Horizontal velocity remains constant. Hence find the resultant velocity.
  9. Apr 5, 2009 #8
    i solved finally, thank you.
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