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!

Potential of Concentric Cylindrical Insulator and Conducting Shell

  1. Sep 10, 2011 #1
    An infinitely long solid insulating cylinder of radius a = 5.3 cm is positioned with its symmetry axis along the z-axis as shown. The cylinder is uniformly charged with a charge density ρ = 45 μC/m3. Concentric with the cylinder is a cylindrical conducting shell of inner radius b = 14.2 cm, and outer radius c = 16.2 cm. The conducting shell has a linear charge density λ = -0.42μC/m.

    1)What is Ey(R), the y-component of the electric field at point R, located a distance d = 44 cm from the origin along the y-axis as shown?

    2)What is V(P) – V(R), the potential difference between points P and R? Point P is located at (x,y) = (44 cm, 44 cm).




    E = Qenc/[itex]\epsilon[/itex]
    E = [2k([itex]\lambda[/itex](cylinder) + [itex]\lambda[/itex](shell))]/r


    [itex]\lambda[/itex]c = [itex]\rho[/itex]*A
    = [itex]\rho[/itex]*2[itex]\pi[/itex]*0.053*0.044
    = 7.0*10^-6 C/m

    E = (2*(8.99*10^9)*(7.0*10^6+(-4.2*10^-7)))/0.44m
    = 268883 N/C


    But that answer is not correct. Please help me! I would appreciate detailed explanation or work, thank you!
     
  2. jcsd
  3. Sep 11, 2011 #2

    diazona

    User Avatar
    Homework Helper

    Surely you don't mean you want someone here to do the work for you?

    Anyway, I see several errors in your calculation:
    That formula is not correct, as you could see if you check the units
    What's k? If you're using [itex]k = \frac{1}{4\pi\epsilon_0}[/itex], then I don't see how you get that formula.


    That line seems right (assuming you meant the c to be a subscript, not a variable on its own)
    but that line is not. Hint: what's the area of a circle? (What does the variable A physically represent?)
     
  4. Sep 11, 2011 #3

    ehild

    User Avatar
    Homework Helper
    Gold Member

    I think A is supposed to be the cross section of the inner cylinder, and ρ its radius. So why ρ*2π? and what is 0.044?

    ehild
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Potential of Concentric Cylindrical Insulator and Conducting Shell
Loading...