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!

Homework Help: Electric field in a cavity in a spherical charge density

  1. May 12, 2017 #1
    1. The problem statement, all variables and given/known data
    A uniform spherical charge density of radius R is centred at origin O. A spherical cavity of radius r and centre P is made. OP = D = R-r. If the electric field inside the cavity at position r is E(r), the correct statement is:
    1)E is uniform, its magnitude is independent of r but its direction depends on r
    is uniform, its magnitude depends on r and direction depends on r
    is uniform, its magnitude is independent of D but direction depends on r
    is uniform and both it's magnitude and direction depend on D.

    2. Relevant equations
    E =
    Where ε is permittivity of medium.
    Electric flux,Φ= q/ε where q is net charge inside gaussian surface.
    3. The attempt at a solution
    I don't even know where to begin

  2. jcsd
  3. May 12, 2017 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Begin by finding the electric field inside a sphere of uniform volume charge density. Then consider superposition. You get zero charge by adding a positive spherical distribution and a negative spherical distribution so if you add a spherical distribution centered at P of opposite charge, you get a cavity.
  4. May 13, 2017 #3
    Thanks. I'll try that
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted