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Homework Help: Electric & magnetic field vector help. E=Bc

  1. Oct 16, 2011 #1
    1. The problem statement, all variables and given/known data
    At one instant, the electric and magnetic fields at one point of an electromagnetic wave are E = 300i + 50j − 200k V/m, and B = Bsub0 (1.7i − 3.9j + ak μT.

    (a) What are the values of a and B0?
    (b) What is the Poynting vector at this time and position?

    2. Relevant equations
    E = Bc
    s = (E x B) / (mu sub0)

    3. The attempt at a solution

    i tried to find Bsub0 using the equation E = Bc for the i and j vectors but the answers are inconsistent. any help would be appreciated
  2. jcsd
  3. Oct 17, 2011 #2
    You know E dot B = 0 that should give you the unknown a. See vector dot product,


    And you know the magnitude of E is related to the magnitude of B, that relationship will give you B_o.

    Good luck!
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