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!

Method of image charges

  1. Mar 2, 2015 #1
    Hi everybody,
    The situation is the classic one: a point charge q+ in a distance d above a conductor plane grounded:
    The conductor is grounded so V = 0, for z = 0.
    Also, far away from the system (x2 + y2 + z2 >> d) V --> 0

    The argument to replace it for a q- charge seems perfect to me.
    What I can't understand why W (potential energy) of the two point charges is twice as much as the conductor plane + q+ charge system.
    I mean, why E = 0 for z < 0 in the conductor plane + q+.
    Thank you a lot!
     
  2. jcsd
  3. Mar 2, 2015 #2

    BvU

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Try Gauss law on the "underside" of the conductor: no charge, no field.
     
  4. Mar 2, 2015 #3
    What do you mean by 'underside', the region immediately bellow the conductor, or a phill box that starts inside the conductor and ends in z < 0?
     
  5. Mar 3, 2015 #4

    BvU

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Both give E = 0.

    The mirror charge method only says something about the region where the real charge is (because a solution to the field equation is unique, anything is allowed, but the solution is only for that region).
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted