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Homework Help: Stopping Potential and kinetic potential

  1. Sep 15, 2013 #1
    [URGENT! Stopping Potential~~~~~~~#######~~~~~~~~~~~~~~~~

    1. The problem statement, all variables and given/known data

    max Kinetic_energy= e*Vs=hf-work_function

    Vs is the stopping potential

    The attempt at a solution

    I am wondering, does this stopping potential refers the voltage difference of
    V_Emitter (where the line shines on) - V_collector(where the electron travels to), and thus, the stopping potential is usually positive?

    Also, for that equation max kinetic_energy= e*Vs, 'e' is just the charge= +ve 1.602*10^-19?
    so that the max kinetic energy in this case, (+5 V)*(+ 1.602*10^-19)= +ve number?

    Attached Files:

    Last edited: Sep 15, 2013
  2. jcsd
  3. Sep 16, 2013 #2


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    2017 Award

    Staff: Mentor

    If you use e as elementary charge, it has to be positive.
    If you use the electron charge, you need the opposite direction, and a negative voltage. That is just a matter of definition.
    What do you mean with "+ve number"? If you add units, you will get the right result.
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