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Homework Help: Electric Field of a Straight Wire at a Particular Distance from Wire

  1. Feb 4, 2012 #1
    1. The problem statement, all variables and given/known data
    See attached document


    2. Relevant equations
    dE=kdQ/r^2
    Ex=Ecos∅

    3. The attempt at a solution
    dE=kdQ/r^2
    E=kλ∫dy/(x^2+y^2) (integrating from y= -L/2 to L/2)
    Ex=2kλ∫xdy/(x^2+y^2)^3/2 (change integration to y= 0 to L/2, multiplying expression by 2)

    Let y=xtan∅
    dy=x(sec∅)^2 d∅

    =2kxλ∫x(sec∅)^2/x^3(sec∅)^3 d∅
    =2kλ/x∫cos∅ d∅
    =2kλ/x(sin∅)
    =2kλ/x(sin(arctan(y/x)) (evaluated from y=0 to y=L/2)
    =2kλ/x(y/(x^+y^2)^1/2 (evaluated from 0->L/2)
    =2kλ/x(L/2)(x^2+(L^2)/4)^.5
    =((1.8X10^10)λL/(2x))*(1/x^2+(L^2)/4)^.5)

    I would appreciate any help or guidance!
     
  2. jcsd
  3. Feb 5, 2012 #2

    tiny-tim

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    Science Advisor
    Homework Helper

    Hi The Head! :smile:
    erm :redface:

    what attached document? :biggrin:

    (and please use the X2 and X2 buttons just above the Reply box :wink:)
     
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