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Vector solution differs mine

  1. Jul 31, 2009 #1
    the shown solution in the link is so different
    http://i30.tinypic.com/35mfo94.gif

    what those vectors represent
    where are they
    why they subtract them
    i totally dont understand thing
    did in a simpler way and got
    a different result
    where is the mistake

    [tex]
    B=\frac{\mu _0 I}{4\pi}\int\frac{ds \hat{r}}{r^2}=\frac{\mu _0 I}{4\pi}\int_{0}^{\frac{2\pi}{3}}\frac{d\theta }{{R_1}^2}
    [/tex]
     
  2. jcsd
  3. Jul 31, 2009 #2

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    Hi electron2! :wink:

    It looks as if you're subtracting them because the first line is for W3, and the second line is for W4, so when you add them, they're in opposite directions, so one comes out negative. :smile:
     
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