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!

Homework Help: HELP! Potential energy of proton in capacitor

  1. Feb 8, 2010 #1
    1. The problem statement, all variables and given/known data

    I have attached the image. The question is --

    What is the potential energy of a proton at the midpoint of the capacitor?

    I know this is an extremely easy problem, but I can't seem to get the formula right...

    2. Relevant equations

    I tried U = qV, using 1.6*10^-19 * 150V (because it is in the middle). What am I doing wrong? Is this not the right formula?

    3. The attempt at a solution

    Attached Files:

  2. jcsd
  3. Feb 8, 2010 #2


    User Avatar
    Gold Member

    Hi and welcome to PF!
    I know a hard way to solve the question. I'm not sure it is of help in your case, but in case you've taken calculus 3 then it's ok.
    [tex]\phi (r)= \int _{\infty}^r \vec E \cdot d \vec l[/tex]. Thus the almost only difficulty would be to calculate the E field between the plates of the capacitor.

    There might be of course a much faster way to solve it. So if anyone can help, welcome!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook