Help with this network analysis question

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Discussion Overview

The discussion revolves around a network analysis problem involving a circuit with a source voltage, resistors, and a dependent source. Participants explore the application of Kirchhoff's Voltage Law (KVL) and the calculation of current through the circuit, while also seeking advice on tackling two-port network problems.

Discussion Character

  • Technical explanation
  • Homework-related
  • Debate/contested

Main Points Raised

  • One participant presents a circuit analysis using KVL, leading to a calculated current of 2.66A, while their teacher claims the answer is 8A.
  • Another participant suggests that the first participant may have made an arithmetic error and confirms their own calculation of 8A using the same equations.
  • Questions are raised about the effect of reversing the polarity of the dependent source on the current, with one participant estimating it to be 1.6A.
  • Participants express difficulties in applying theorems in circuit analysis, particularly in two-port network problems, and seek advice on how to approach these types of problems.
  • One participant suggests remembering whether to short or open circuit a port and recommends using reference materials for assistance.

Areas of Agreement / Disagreement

There is disagreement regarding the correct current calculation, with one participant asserting 2.66A and another confirming 8A. The discussion on the effects of reversing the polarity of the dependent source remains exploratory, and participants express varying levels of uncertainty regarding two-port network analysis.

Contextual Notes

Participants have not reached a consensus on the correct current value, and there are unresolved questions about the application of circuit analysis techniques and the specifics of two-port network problems.

Who May Find This Useful

Students and individuals studying electrical engineering or circuit analysis, particularly those struggling with KVL applications and two-port network concepts.

Pratik77
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given:
source voltage =120V
voltage across 15 ohm resistor = Va
there is a dependent source 2Va
and a 30 ohm resistor.


I tried applying KVL i.e 120-30I+2Va-Va=0
where Va=15I

and got I=2.66A
whereas my teacher told me that the answer is 8A. how is it so? Is it some basic knowledge that I have overlooked?
Also as a side note, I have difficulty knowing which theorem to apply in which circuit. I do practise problems but even then I have difficulties especially in chapters like 2-port network. Are there any tips regarding that?
 
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Pratik77 said:
I tried applying KVL i.e 120-30I+2Va-Va=0
where Va=15I

and got I=2.66A
whereas my teacher told me that the answer is 8A.

Show your working. I think you just made an arithmetic error. I used your equations and get 8A.
 
Umm.. yep you are correct. what would have been the current if the polarity of 2Va was reversed?
Do you have any advice on how to deal with two port network problems. I just don't know how to approach the problems for the asked parameters(z,y,h,etc.)
 
Pratik77 said:
Umm.. yep you are correct. what would have been the current if the polarity of 2Va was reversed?

I made that 1.6A.

Do you have any advice on how to deal with two port network problems. I just don't know how to approach the problems for the asked parameters(z,y,h,etc.)

Usually it's a matter of remembering if you should short or open circuit a port and then working out the effect of that on the circuit. Perhaps print out some of the slides from here to have as a reference?..

http://www.slideshare.net/PinkyChaudhari/two-port-network

If I've misunderstood perhaps start a new thread with an example.[/quote][/QUOTE]
 
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Thanks!
 

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