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Photoelectric effect

  1. Sep 21, 2012 #1
    Hi everyone, a quick question on photoelectric effect.

    Why measure stopping voltage by connecting a battery to the circuit and then adjust until current reach 0? Cant we just use a voltmeter?

    Thank you!
  2. jcsd
  3. Sep 21, 2012 #2


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    In theory, you could wait until all the photo-electrons generate the voltage themself - but that would require so many photo-electrons that it is not practical. In addition, no isolation is perfect (especially with an attached voltmeter), the system would discharge itself.
  4. Sep 21, 2012 #3
    Thanks. After some thinking I guess there is also the problem that not all electrons released have the theoretical maximum energy, so the potential get from a voltmeter will be biased
  5. Sep 22, 2012 #4


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    The distribution in velocities will just mean that it takes longer to reach the maximum voltage - the low velocity electrons will play no part in the process once the voltage is greater than their particular stopping voltage.
    Finding the value of V that will stop the current would be a more practical way, I think - which is why it's recommended.
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