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Homework Help: Some Electricity Questions!

  1. Mar 9, 2010 #1

    bon

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    1. The problem statement, all variables and given/known data

    1) Where I(t) = Iocoswt, and V' is the voltage across an inductance V' = L dI/dt, Im asked to work out the time average of <I V' >..

    when i work it out, the answer comes to zero...any ideas why?

    2)I'm asked to sketch I(t) = Acos(w1 t)cos(w2 t) where w2 << w1...

    is this just fast oscillations of speed (w2) within a boundary that is itself oscillating (more slowly..) ? so a cos graph within a cos graph with bigger period?

    3) Find the bandwith of the signal I(t) = A cos^2 (wt) cos(10wt)..

    I know bandwith is the randge of angular frequencies present in I, but here its not just 10wt-wt is it? How do I work it out?

    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Mar 9, 2010 #2

    bon

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    no ideas?
     
  4. Mar 10, 2010 #3

    bon

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    anyone?
     
  5. Mar 10, 2010 #4
    No power is dissipated in a network with only inductors and capacitors.

    yes

    cos^2 (wt) is also a product of two cosines, so you can replace it with a sum involving
    cos (0) and cos (2wt)
     
  6. Mar 10, 2010 #5

    bon

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    Just a quick questionn about I = Acos(w1 t)cos(w2 t) one..

    so w2 << w1 so would w2 be the outer shell, and w1 be the inner, fast oscillations.. how would you describe this?
     
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