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Some Electricity Questions!

  • Thread starter bon
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  • #1
bon
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Homework Statement



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?

Homework Equations





The Attempt at a Solution

 

Answers and Replies

  • #2
bon
559
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no ideas?
 
  • #3
bon
559
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anyone?
 
  • #4
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228

Homework Statement



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?
No power is dissipated in a network with only inductors and capacitors.

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?
yes

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?
cos^2 (wt) is also a product of two cosines, so you can replace it with a sum involving
cos (0) and cos (2wt)
 
  • #5
bon
559
0
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)
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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