1. Not finding help here? Sign up for a free 30min 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!

Work and electric potentials confused

  1. Jun 21, 2004 #1
    Living cells actively pump sodium ions inside the cell to outside the cell. Given that the electric potential is 0.070V higher outside the cell than inside the cell and that the cell membran is 0.09E-6 meters thick, how much work must be done to move one sodium ion from inside the cell to outside the cell.


    So far I am lost, does voltage have to negative, but then negative work has to be done
     
  2. jcsd
  3. Jun 21, 2004 #2
    Signs are a matter of luck :wink:

    Apart from that this seems not too difficult. Note that the thickness of the wall makes no difference.
     
  4. Jun 21, 2004 #3

    Doc Al

    User Avatar

    Staff: Mentor

    Are you positive?

    It requires positive work to move a positive charge from a low to a high potential. (Just like it requires positive work against gravity to lift an object.)

    So what's the charge on the sodium ion?
     
  5. Jun 21, 2004 #4
    positive 0.070?
     
  6. Jun 21, 2004 #5

    Doc Al

    User Avatar

    Staff: Mentor

    A sodium ion is formed by removing an electron. So the charge of the ion is +e = 1.6 E-19 Coulombs.
     
  7. Jun 21, 2004 #6
    so is the answer 0.070 * 1.6*10^-19 ?
     
  8. Jun 21, 2004 #7

    Doc Al

    User Avatar

    Staff: Mentor

    Yes. Don't forget to use the proper units: work is measured in Joules.
     
  9. Jun 21, 2004 #8
    thank you so much :)
     
  10. Jun 21, 2004 #9

    turin

    User Avatar
    Homework Helper

    I didn't catch that at first ( :redface: ). I wonder if it was on purpose.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Work and electric potentials confused
Loading...