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: Surface integral without using Gauss's Theorem

  1. Sep 8, 2010 #1
    1. The problem statement, all variables and given/known data

    Find the value of the surface integral [tex]\int[/tex]A [tex]\bullet[/tex] da, where A = xi - yj + zk, over the surface defined by the cylinder c2 = x2 + y2. The height of the cylinder is h.

    2. Relevant equations

    I found the answer quite easily using Gauss's theorem, as the divergence of the vector A is simply 1, so the volume integral reduces to [tex]\int[/tex]dv, which just becomes the volume of the cylinder. However, I was wondering how to integrate directly without using Gauss's theorem; i.e., integrate the original surface integral [tex]\int[/tex]A [tex]\bullet[/tex] da. I feel like this is a pretty simple question and I'm thinking way too hard.
  2. jcsd
  3. Sep 8, 2010 #2


    User Avatar
    Homework Helper
    Gold Member

    Divide the cylinder's surface up into 3 pieces: two endcaps and one curved surface. What is [itex]d\textbf{a}[/itex] for each of these 3 pieces? What variables change over each surface, which stay the same (and what are their fixed values)?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook