How do dependent sources change the analysis of a circuit?

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Discussion Overview

The discussion revolves around the analysis of circuits containing dependent sources, particularly focusing on how these sources affect circuit behavior and the methods for analyzing such circuits. The scope includes homework-related questions and technical explanations regarding circuit analysis techniques like KCL (Kirchhoff's Current Law) and Thevenin's theorem.

Discussion Character

  • Homework-related
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant expresses confusion about how to approach a circuit with a dependent source, questioning whether to start with KCL on a specific loop.
  • Another participant confirms that starting with KCL is indeed the correct approach.
  • A different participant shares their struggle with understanding the impact of additional components on the open circuit voltage, suggesting that one can ignore certain elements when analyzing the circuit.
  • One participant proposes a step-by-step method to find the Thevenin equivalent of a circuit involving a current source and resistors.
  • Another participant advises on how to determine the Thevenin voltage (Vth) and resistance (Rth), emphasizing the need to consider the independent voltage source and the implications of current flow in the circuit.

Areas of Agreement / Disagreement

Participants generally agree on the need to apply KCL and Thevenin's theorem in the analysis, but there are varying interpretations of how to handle specific components and assumptions in the circuit. The discussion remains unresolved regarding the best approach to analyze the circuit with dependent sources.

Contextual Notes

Participants express uncertainty about the role of certain components in the circuit and the implications of dependent sources on voltage and current measurements. There are also assumptions about current flow that are not fully explored.

Who May Find This Useful

Students and individuals studying circuit analysis, particularly those encountering dependent sources for the first time or seeking clarification on Thevenin's theorem and KCL applications.

siylence
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Homework Statement



theveniandep.png

Homework Equations


v = IR

The Attempt at a Solution



Okay, so up until this point, I was doing okay... but now I'm stuck.

I do not understand how I'm supposed to work with this because until now I have not had a dependent source.

Am I supposed to start by doing a KCL on the loop to the left?

Also, this may sound stupid, but on the resistor that is running in parallel, why is there a +/- Vz symbol? Is it just there to point direction of current flow or am I missing something?
 
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Am I supposed to start by doing a KCL on the loop to the left?

Yes.
 
This always tripped me up too. You see, there's all this stuff on that top node and you are supposed to find the open circuit voltage? Geez. Why is all that stuff there, how can that not be a factor in the open circuit voltage?

So, your assumption is correct! Since the loop to the left is open, you just imagine that stuff is gone and you are just trying to find the voltage across that one resistor (Vz). Since there is a current source...I think you know what to do.
 
1st:
find the Th. equivalent for the 8A-3ohm-2ohm circuit.
2nd:
connect the equivalent in series with 4ohm-5Vz
 
You can Ignore everything in the branch from the node to port 'a' because current will not travel somewhere that will trap it. After, you analyze what you have left and see what you need. So you need Vth and Rth. To find Rth, zero out your independent SOURCES, then find the Req. Then Rth will equal Req. To find Vth don't assume it is = Vz. Why? because Vth is measured at the terminal 'a' to 'b'. We said there is no current through the branch from node to 'a' so there is no voltage drop through the 4ohm resistor BUT there is a voltage independent voltage source so you will have to deal with that to find the Vth
 

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