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!

Electrostatics problem

  1. Sep 17, 2009 #1
    1. The problem statement, all variables and given/known data
    A spherical shell of radius R with uniform charge Q is expanded to a radius H.find the work done by electric forces during the shell expansion
    given answer is 1/(8pi epsilon) *Q^2(1/R-1/H)
    my attempt
    work=-change in P E
    =1/(4pi epsilon) *Q^2(1/R-1/H)
    plz explain the additional 1/2 factor
  2. jcsd
  3. Sep 17, 2009 #2


    User Avatar
    Homework Helper

    Here you have to consider the energy stored in a spherical capacitor.
    What is the capacity of a spherical conductor?
    What is the energy stored in a capacitor?
  4. Sep 18, 2009 #3
    what is the mistake in my approach?
    why not take change in potential energy as work done?
  5. Sep 18, 2009 #4


    User Avatar
    Homework Helper

    Because the electric field in continuously changing during the expansion of the spherical conductor. To find the total work done you have to take the integration.
    Energy stored in the capacitor= 1/2*Q^2/C
    Capacity of the spherical conductor = 4πεοR
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Electrostatics problem
  1. Electrostatics problem (Replies: 1)

  2. Electrostatics problem (Replies: 2)

  3. Electrostatic problem (Replies: 4)

  4. Electrostatics problem (Replies: 2)

  5. Electrostatics Problem (Replies: 5)