1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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


    User Avatar
    2017 Award

    Staff: Mentor

    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


    User Avatar
    Science Advisor
    Gold Member
    2017 Award

    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.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook