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Homework Help: B-field from E-field

  1. Mar 28, 2009 #1
    1. The problem statement, all variables and given/known data

    E = 20 cos([tex]\omega[/tex]t-50x) [tex]\widehat{y}[/tex] find H in free space?

    2. Relevant equations

    I used ([tex]\nabla[/tex] X E ) = -dB/dt , and then integrated that expression with respect to t , for some reason I am getting an incorrect answer ?!

    3. The attempt at a solution

    the correct answer is H = 0.4 w*(eps) *cos([tex]\omega[/tex]t-50x) [tex]\widehat{z}[/tex]
    Last edited: Mar 28, 2009
  2. jcsd
  3. Mar 29, 2009 #2


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    Gold Member

    remember that H and B are not the same.

    D = eps*E
    H = B/mu


    ( [tex]\nabla[/tex] X H ) = -dD/dt

    or for linear media:

    ( [tex]\nabla[/tex] X B ) = mu*eps*dE/dt

    also remember that the curl pertains to spatial, not temporal derivatives.
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