Electrical Engineering - circuits - Reactive Networks

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  • #51
gneill
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@gneill also do we now take into account the current source and resistor on the left? since there is no longer a short circuit, as there will now be a current source there
No. The short still divides the two circuits.

Here's the situation with the Thevenin model in place:

upload_2016-1-30_13-31-11.png


Replace the Thevenin model with a Norton model. What do you get?
 
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  • #52
Thanks! Any idea for part D and E as im stumped :(
 
  • #53
gneill
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Thanks! Any idea for part D and E as im stumped :(
I'll need to see an attempt from the OP before I can share :smile:
 
  • #54
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Sorry about the delay, only just had a chance to give part C a go!

I'm feeling a bit more sure about this part, but I've attached my work anyway just to be sure
20160131_195513.jpg
 
  • #55
gneill
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Ah. You've mixed the Thevenin model with the original circuit there. You can't just drop the Thevenin voltage into the original circuit as it already expresses the effects of the other components.

You can, on the other hand, start with the entire Thevenin equivalent circuit and proceed from there. A Thevenin equivalent entirely replaces the original circuit and exhibits the same behavior. So you can convert the Thevenin model directly to a Norton equivalent.
 
  • #56
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So would this be the correct conversion?

20160131_201623.jpg
 
  • #57
gneill
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Yes. It's common practice to rename ##Z_{th}## to ##Z_N## for the Norton model, even though they have the same value.
 
  • #58
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So as for the calculations, where I've previously used Zc, should I just use Zth to work out In?
 
  • #59
gneill
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So as for the calculations, where I've previously used Zc, should I just use Zth to work out In?
Yes. Once you've got the Thevenin equivalent you can throw out the original circuit and never look at it again :smile:
 
  • #60
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I've re-done my calculations using Zth instead of Zc, does this look better?
20160131_214943_0.jpg
 
  • #61
gneill
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Your Thevenin Impedance ##Z_T## looks very odd. Where did it come from ?
 
  • #62
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I added the impedance of the capacitor and inductor, is this not the correct method?
 
  • #63
gneill
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I added the impedance of the capacitor and inductor, is this not the correct method?
We examined that before. How are those components connected to each other when the voltage supply is suppressed?
 

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