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!

Confused by surface charge and voltages

  1. Oct 1, 2012 #1
    How can a conducting sphere have no voltage at the surface, and yet have a surface charge when there's a charge outside of the sphere? Wouldn't the surface charge create voltage at the surface?
  2. jcsd
  3. Oct 2, 2012 #2


    User Avatar
    Science Advisor
    Gold Member
    2017 Award

    A conducting sphere means that it consists of a material, where charges are (quasi-)free to move around. Thus, if you bring a charge distribution outside of the sphere, their electromagnetic field acts on the free-moving charges such that in the stationary limit the sphere becomes a surface of constant electric potential, because then and only then the tangent components of the electric field vanish along the sphere, and this they have to, because in the stationary limit there must be no current along the surface, and there was a current, if the tangent components of the electric field were not vanishing because of Ohm's Law [itex]\vec{j}=\sigma \vec{E}.[/itex]
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook