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: Potential of a conducting sphere with charge inside

  1. May 14, 2010 #1
    This is a general question:

    What is the electric potential of a hollow neutral conducting sphere with radius R with a charge q placed inside it?
    Intuitively I understand that it is the same - q/R, no matter where the charge is placed inside the sphere. Can anyone explain why it is so?

    My thoughts: The potential on the surface of a conducting sphere is constant, and it seems implausible that I will be able to change the potential of the sphere just by moving the charge inside, and therefore, I may as well place it in the middle and then the potential is obviously q/R.
  2. jcsd
  3. May 14, 2010 #2


    User Avatar
    Homework Helper
    Gold Member

    Hint: What would you expect the charge distribution to "look like" when you are very far from the sphere? What is the total charge enclosed by a spherical, concentric Gaussian surface of radius r>>R? So, if the potential at r=infinity is zero, what must the potential be at any point outside the sphere?
  4. May 15, 2010 #3

    I've found a comprehensive and detailed explanation in Griffiths Intro to Electrodynamics. Should have known it'll be there - gotta love that book!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook