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Homework Help: Flux integral help

  1. Nov 12, 2007 #1
    1. The problem statement, all variables and given/known data
    Well, I'm trying to take advance in my course and learn about how to calculate flux integrals. I have a few problems I can try out but I can't seem to understand the method they are using to solve the problems.

    2. Relevant equations

    I don't know..

    All I have is int(surface) v x dA

    3. The attempt at a solution

    For example, I tried doing one of the problems. The question asks me to find the flux of the vectorial field through the surface.

    F = yj through the square of sides 4 in the plane y=5. The square is centered on the y axis, its sides are parallel to the axis' and is oriented in the positive y direction.

    Now I was trying to figure out some sort of method of how to solve problems like these.

    This is what I did. I replaced y=5 in the equation F=yj and then multiplied it by the orientation which gave me F = 5. In this case, my dA was jdxdy.

    From there, I had a double integral such as int(0,4) int(0,4) F x dA.

    int(0,4) int(0,4) 5dxdz = 80

    That does give me the correct answer but I want to know if the way I got to it is correct. If its not, are there any equations or other information that I should know about. None are given in the book :(.

  2. jcsd
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