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!

Surface current density

  1. Jun 24, 2015 #1
    Surface current density, K is defined as:
    K = σv
    where σ is surface charge density and v is velocity.

    Given a uniformly charged spherical shell with radius R, spinning at constant angular velocity ω, find the current.

    So, I start with this formula:
    dI = K dl
    dI = σ Rω dl
    and I placed the spherical shell at cartesian coordinate with its center at origin and try to solve the question in spherical coordinate.

    What path should I take to express dl? Professor explained, dl = R dθ. What I don't understand is, why do we have to take R? Why not R sin(θ)?
     
  2. jcsd
  3. Jun 24, 2015 #2

    PeroK

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    What might "uniformly" charged mean in this case? Imagine you had 10 wires wrapped round the upper hemisphere. You could do that "uniformly" in two different ways.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook




Loading...