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: E field of sphere

  1. Sep 5, 2011 #1
    1. The problem statement, all variables and given/known data

    A nonconducting solid sphere of radius (R) .1m has uniform volume charge density (2*10^-6 C/m^3 was calculated and verified accurate). Find the magnitude of the e field at a distance (r) .05m from the sphere's center.

    2. Relevant equations3. The attempt at a solution
    flux=E*4*pi*r^2 = Q/Eo
    I calculated Q by multiplying the volume charge density by its volume (4/3)*pi*(.1^3) which got me 8.38e-9 C.

    I solved for E=Q/(Eo * 4 * pi * r^2) which got me 30000 N/C. But that answer was 470 N/C. What did i do wrong?
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Sep 6, 2011 #2
    you have to use the electric field inside the sphere since r=0.05 m is less than the radius
    R= 0.1 m. Electric field inside the sphere at a distance r from the center is

    [tex]E(r)=\frac{1}{4\pi \epsilon_o}\;\frac{Q}{R^3}\;\; r[/tex]

    where Q is the total charge

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook