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Homework Help: The work done by an electric field in accelerating a charged particle?

  1. Dec 31, 2012 #1
    1. The problem statement, all variables and given/known data
    A particle with a charge of 3.2x10^-19 C accelerates from rest between two charged plates. The electric field is uniform and is 39000 N/C. The distance between the plates is 4.5x10^-3 m.

    A) Calculate the force on the particle
    B) How much work is done by the electric field in accelerating the particle between the two plates?
    C) What is the increase in kinetic energy of the particle?
    D) What is the change in potential energy of the particle?

    2. Relevant equations

    My answers so far:

    A) Using F=QE to get an answer of 12fN

    B) I'm not sure on the validity of this answer, or infact the right equation to use for this question and parts B and C.

    I've used WD = FxD
    Therefore, an answer of 56.2 aJ

    C) Would the increase in kinetic energy be simply the change in energy experienced for part B)?

    Any help would be greatly appreciated!
  2. jcsd
  3. Dec 31, 2012 #2
    A) correct!
    B) correct!
    C) You are right!
    D) The change in P.E. will be equall to minus the gain in K.E. (conservation of energy)
  4. Dec 31, 2012 #3
    So both part B and C have the same answers of 56.2 aJ?

    For D would the answer be along these lines?

  5. Dec 31, 2012 #4
    Since the particle acquires a P.E. because of the work done on it and this is converted to K.E., so the answer to (D) is << solution deleted by Mentor -- but use his hint to fix your answer... >>
    Last edited by a moderator: Dec 31, 2012
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