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: Electric field around a wire

  1. Sep 14, 2010 #1

    Uku

    User Avatar

    1. The problem statement, all variables and given/known data
    I know that around an infinitely long wire with even charge distribution the electric field is expressed as:

    [tex]E=\frac{1}{2\pi\epsilon_{0}}\frac{\lambda}{r}[/tex] (1)

    Where [tex]\lambda[/tex] can be expressed as [tex]\lambda=\frac{dq}{dl}[/tex]

    Right, but I want to know where I get this formula from, I mean the E field.

    3. The attempt at a solution

    So I know that in general:

    [tex]E=\frac{1}{4\pi\epsilon_{0}}\int\frac{\rho}{r^{2}}\widehat{r}dV[/tex]

    In my case I don't have volume, I have a thread. I can also forget about the unit vector, since the field is radially pointed outward. The charge is evenly distributed so I can write:

    [tex]E=\frac{1}{4\pi\epsilon_{0}}\lambda\int\frac{1}{r^{2}}dL[/tex]

    Okay, but now... I can integrate the expression from minus infinity to infinity, but how do I get to that formula (1)
     
  2. jcsd
  3. Sep 14, 2010 #2
    You can find a number of sites that work this out for you. A google search, or even a search here at PF will give you many looks at this problem. Here is one, for example.

    http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elelin.html
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook