1. Not finding help here? Sign up for a free 30min 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!

Coaxial Cable Problem - Finding volume charge density.

  1. Sep 18, 2013 #1
    1. The problem statement, all variables and given/known data

    A long coaxial cable consists of an inner solid cylinder, radius a, and an outer thin coaxial cylindrical shell, radius b. The outer shell carries a uniform surface charge density σ.
    Find the uniform volume charge density ρ that the inner cylinder must have in order that the whole cable (inner + outer) is neutral.

    2. Relevant equations

    Acylinder = 2πbl

    Vcylinder = πa^2l

    Qenc = ∫Vρdτ

    3. The attempt at a solution


    I started by using dq = sigma*dS, and integrating to get Q_b = -2(pi)(sigma)bL. That should be the total charge on the outer cylindrical shell.

    Then I set -Q_b = Q_a, so the net charge of the entire system would be equal to 0.

    Next I used Q_a = row*integral(dVolume) = -Q_b

    to get to (row)(pi)(a^2)(L) = 2(pi)(sigma)(b)(L)

    Solving for row gave me:

    row = [2(sigma)(b)] / a^2


    Does this look like a proper method and correct solution?

    Thank you so much for your time.

    WJ
     
  2. jcsd
  3. Sep 18, 2013 #2

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    That looks right.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Coaxial Cable Problem - Finding volume charge density.
  1. Coaxial cable (Replies: 2)

Loading...