Using source transformation for dependent sources

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Discussion Overview

The discussion revolves around the application of source transformation techniques in circuits involving dependent sources. Participants explore the implications of using source transformations to analyze circuit behavior and address discrepancies in results obtained through different methods, such as nodal analysis.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant questions the feasibility of using source transformation for dependent sources, suggesting it is possible based on a specific problem.
  • Another participant notes a discrepancy between their answer obtained through source transformation and the result from voltage node analysis, prompting a discussion on the reliability of these methods.
  • A participant explains that transforming away a component related to a controlled source can lead to differences in voltage or current, emphasizing that the overall behavior at the output remains consistent.
  • Several participants express confusion over the placement of voltage drops in their analyses, particularly regarding the relationship between voltage drops and specific resistors in transformed circuits.
  • One participant highlights that the node where resistors connect remains a valid reference point despite transformations, which may clarify some misunderstandings about circuit behavior.
  • Another participant shares a link to an external solution that they believe correctly addresses a similar problem, indicating a search for validation of their approach.

Areas of Agreement / Disagreement

Participants express differing views on the application of source transformation in circuits with dependent sources, with some agreeing on the challenges it presents while others remain uncertain about the correct approach. The discussion does not reach a consensus on the best method for analysis.

Contextual Notes

Participants note limitations in their understanding of how transformations affect circuit components and reference points, indicating a need for clarity on the implications of these transformations in circuit analysis.

Who May Find This Useful

This discussion may be useful for students and practitioners of electrical engineering or circuit analysis, particularly those grappling with the complexities of dependent sources and source transformation techniques.

Saeed.z
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Hi all ,

is it possible to use the source transformation for dependent source ..?

i guess yes because i came across a problem which asks to use source transformation to find Vx as shown :

http://img571.imageshack.us/img571/2389/50111057.jpg

and my solution was :

http://img36.imageshack.us/img36/7417/ansu.jpg

thanks ..:smile:
 
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BTW, i checked my answer by using Voltage node analysis and found that Vx = 7.5 V !

why the 2 answers are different ? thanks
 
You "transformed away" the component that the controlled source referred to. When you make a transformation there's no guarantee that the "new" components will have the same voltage or current as the "old" components they replace, only that the overall behavior at the output of the transformed block of components will be the same.
 
Hi I was also having trouble with a similar problem I was working on and solved it in a similar manner to the poster with the same issues arising of getting a different answer than when using nodal analysis. I found a similar problem online that gets the correct solution:
The solution is online under example 2 at http://waleedeid.tripod.com/Lecture7_cir_analysis.pdf
(sorry my browser won't let me copy the image into the post).

My question is why did he make the voltage drop vx across the the 3V source and the 1Ohms resistor? When I did the problem I only put the voltage drop across the 1 Ohm resistor because I though R(Norton) = R(thevnin).
 
sandmanumd said:
Hi I was also having trouble with a similar problem I was working on and solved it in a similar manner to the poster with the same issues arising of getting a different answer than when using nodal analysis. I found a similar problem online that gets the correct solution:
The solution is online under example 2 at http://waleedeid.tripod.com/Lecture7_cir_analysis.pdf
(sorry my browser won't let me copy the image into the post).

My question is why did he make the voltage drop vx across the the 3V source and the 1Ohms resistor? When I did the problem I only put the voltage drop across the 1 Ohm resistor because I though R(Norton) = R(thevnin).
See my post immediately above yours. If you transform away a specific component then you can no longer use that component as a reference. Doesn't matter if a "replacement" component has the same numerical value; it's a different component in a different circuit configuration.

The only thing guaranteed is that the OUTPUT TERMINALS of the transformed circuit block will behave the same as the original.

In your referenced example, Vx is not so much associated with a particular 2Ω resistor but the NODE where all the resistors come together. That node remains despite the source transformations that take place, so it remains a "safe" reference point.

attachment.php?attachmentid=45375&stc=1&d=1332425616.gif
 

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o ok, I see that now and understand. Thanks so much for all your help!
 
Thanks all of you for your help , i appreciate that !

BTW i got the same answer here :

http://img715.imageshack.us/img715/6691/ee1w.png

http://img198.imageshack.us/img198/2976/ee2u.png

thanks again :)
 
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