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!

Gauss' Law With an Infinite Cylinder of Charge

  1. Oct 27, 2007 #1
    [SOLVED] Gauss' Law With an Infinite Cylinder of Charge

    1. The problem statement, all variables and given/known data

    The test question was to find the potential difference between a point S above a cylinder of charger per length lambda, and a point on the surface of the cylinder having radius R and infinite length.

    2. Relevant equations

    Stupid me tried to grind through it during the test. But looking at the prof's solution:

    http://www.phys.washington.edu/users/schick/321A/321-07exam1soln.pdf

    Here's the test if you need to know the question how he worded it:

    http://www.phys.washington.edu/users/schick/321A/321-07exam1.pdf

    Problem #1.

    I don't get how he got "E(s)*2pi*L*S

    I get the 2pi and L come from integrating over phi and the length of the cylinder, but I can't figure out where that S came from.


    Is it because you'd need a cosine(theta) for the direction that the cylinder is from S? Where cosine is S/distance? Then wouldn't he have to add in a bunch of other stuff? I'm just not seeing something here and I feel embarrassed.
     
  2. jcsd
  3. Oct 27, 2007 #2
    [tex]\int E \cdot dA = EAcos(\Theta)[/tex]

    Where [tex]\Theta[/tex] is the angle between the surface of the cylinder and the electric field.

    Now, simplify this last expression. What is A? What is [tex]\Theta[/tex]?
     
  4. Oct 27, 2007 #3
    Ohhhhhh I get it. A is 2pi*Length*radius, and he's just using S as the radius, since it shouldn't matter.

    Gotcha, thanks a bunch.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Gauss' Law With an Infinite Cylinder of Charge
Loading...