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: Compute flux through rectangular area

  1. Mar 15, 2010 #1
    1. The problem statement, all variables and given/known data

    There is an aXb rectangular area in the same plane as a wire with current I. The wire is parallel to side b, and a distance d away. Compute the flux through the rectangular area.

    2. Relevant equations



    cylindrical coordinates... rdrd[tex]\theta[/tex]dz
    3. The attempt at a solution

    dr is from d to d+a
    d[tex]\theta[/tex] is from 0 to 2[tex]\pi[/tex]
    dz is from 0 to b

    The solution to this ends up having natural logs in it, and to do that I would have to drop r, but I don't feel like that is right. Could someone please help point me in the right direction on setting up this integral.

    Thank you.
  2. jcsd
  3. Mar 15, 2010 #2
    Re: flux

    I am not sure why some things look like subscripts or exponents so just a warning there are no exponents are subscripts lol
  4. Mar 16, 2010 #3
    Re: flux

    I think I see why now. I should be using rectangular coordinates huh?
    I don't know what I was thinking... I must have been thinking partially of amperes law
  5. Mar 16, 2010 #4
    Re: flux

    ([tex]\mu[/tex]I)/(2[tex]\pi)[/tex][tex]\int[/tex][tex]\int[/tex](1/r) dr dy

    dr from d to d+a
    dy from 0 to b

    would this be the correct set up?
  6. Mar 16, 2010 #5


    User Avatar
    Homework Helper

    Re: flux

    Yes, that's the correct setup. Your solution should have a natural log in it.
  7. Mar 16, 2010 #6
    Re: flux

    [tex]\frac{ \mu I }{2\pi} \int_0^b \int_d^{d+a} \frac{1}{r} dr dy [/tex]

    Code (Text):

    \frac{ \mu I }{2\pi} \int_0^b \int_d^{d+a} \frac{1}{r} dr dy
    Hope that helps, though it's nothing to do with the actual question.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook