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!

Electric Potential rank

  1. Jul 27, 2014 #1

    Zondrina

    User Avatar
    Homework Helper

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

    Rank the electric potential energy at point ##P## for the following four cases:

    http://gyazo.com/c7d9df3d3d64cda909ddc0d2ab7686bc

    2. Relevant equations

    ##\Delta U_e = - W_∞##

    3. The attempt at a solution

    I believe it should be ##U_2 > U_1 > U_3 > U_4##, but I am not certain.
     
  2. jcsd
  3. Jul 27, 2014 #2

    ehild

    User Avatar
    Homework Helper
    Gold Member

    Why do you think what you believe? How is electric potential defined? And what is the electric potential at distance r from a point charge q?

    ehild
     
  4. Jul 27, 2014 #3

    Zondrina

    User Avatar
    Homework Helper

    Ah I see, so ##V = k \frac{q}{r}## in combination with ##V = \frac{U_e}{q}##.

    This yields ##U_2 > U_1 = U_3 = U_4##.

    Thank you.
     
  5. Jul 27, 2014 #4

    ehild

    User Avatar
    Homework Helper
    Gold Member

    The solution is correct now.

    Yes, the potential is the potential energy of a unit positive charge at a certain point of the electric field. It is defined with the work done by the field:
    The potential at a point P is equal to the work done by the electric field on a unit positive charge while it moves from P to the place where the potential is zero.

    You know from Gauss Law that the electric field around a charge q is E=kq/r2. It is a conservative field. The potential U(r_P) is the work on a unit positive charge when it moves from rP to infinity: [tex]U(r_P)=W\big |_{r_P}^{\infty}=\int _{r_P}^{\infty}{\frac{kq}{r^2}dr}=k\frac{q}{r_P}[/tex].

    ehild
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Electric Potential rank
  1. Electric potential (Replies: 1)

Loading...