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: Charge Density (rod)

  1. Feb 26, 2007 #1
    Never mind, i got it, whew



    1. The problem statement, all variables and given/known data
    http://img137.imageshack.us/img137/6250/chargqg0.th.jpg [Broken]
    The rod has a nonuniform charge density lambda = ax (a is a positive constant). Find electric potential at point A.
    2. Relevant equations
    V = kq/r
    E = kqq/r^2
    V = -[tex] \[ \int_a^b E dot dr\] [/tex]

    3. The attempt at a solution
    I am pretty close to the answer, I'm just not quite there.
    If I'm not mistaken it is something like:
    [tex] \[ \int_d^{L+d} kax*r/r^2\,dr [/tex]
    but I'm not quite sure what to do with the 'x', from the answer, I know that it has to end up being the integral of 1/r, so x can't be r because it would end up being just the integral of dr

    Maybe the limits are incorrect?
     
    Last edited by a moderator: May 2, 2017
  2. jcsd
  3. Feb 24, 2008 #2
    Hi! I have a similar problem...

    A rod of length L lies along the y-axis with its center at the origin. The rod has a nonuniform linear charge density lambda =a | y | , where a is a constant with the units {\rm C}/{\rm m}^{2} . Determine the constant a in terms of L and the rod's total charge Q.

    I know that for uniform charge its lambda=L*Q and then integrate but what do I do in this case?

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