Attempt at Thevenin Equivalent Circuit

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Discussion Overview

The discussion revolves around determining the Thevenin equivalent circuit, specifically focusing on finding the open-circuit voltage (Voc) and Thevenin voltage (Vth) in a given circuit involving capacitors, inductors, and dependent sources. Participants explore various methods and approaches to solve the problem, including superposition and impedance calculations.

Discussion Character

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

Main Points Raised

  • One participant describes their process of converting voltage sources to rectangular format and using KCL to find voltages at specific nodes.
  • Another participant requests clarification on the results and terminology used, specifically questioning the meaning of Vd and suggesting it might be Vb.
  • A participant inquires about the current through the inductor during the open circuit condition, highlighting a lack of information regarding this current.
  • One participant expresses confusion about whether the Thevenin impedance (Zth) is equivalent to the load resistor between nodes A and B, proposing that they could use Zth to find the voltage across the inductor.
  • Another participant asserts that in an open circuit, the current through the inductor would be zero, reinforcing the idea that no current flows due to infinite resistance.
  • A later reply confirms that there is no voltage drop across the inductor in the open circuit condition, supporting the previous assertion about current flow.
  • In a concluding post, one participant claims to have solved for Voc, stating that VL is 0V and thus Vth equals 1V, while expressing initial uncertainty about the problem.

Areas of Agreement / Disagreement

Participants generally agree that in an open circuit condition, the current through the inductor is zero, leading to no voltage drop across it. However, there are differing views on the methods to find Vth and the implications of Zth, indicating that multiple approaches and interpretations remain in the discussion.

Contextual Notes

Some participants mention specific terminology used in their course, which may not be universally understood. There are also unresolved aspects regarding the initial conditions and assumptions about the circuit elements.

Who May Find This Useful

Students and practitioners interested in circuit analysis, particularly those studying Thevenin's theorem and its applications in electrical engineering.

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Hi, I am having trouble trying to determine Voc on this circuit.
I have done the following to attempt it:

1) Converted my Voltage source to rectangular format (from polar)
2) Converted my capacitor and inductor to Xc and XL
3) I tried using KCL to find Va that's at the three-way on the circuit, with ground node put at the bottom of Vd.
4) I've done method 3 of Thevenin equivalent circuits (using Vtest at nodes a and b of the circuit, shorting my voltage source, and solving for Zth anyway).

I just can't wrap it around my head how to find Vth knowing that my current source requires voltage off of the inductor.

I've asked one of my professors from another class and he told me to use superposition, but it doesn't make sense to me either.

Any help would be greatly appreciated, thank you!
 

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It would help if you showed your results so far. This way you can get some feedback.
b?
Also, what is Vd? Did you mean Vb?
 
What is the current through the inductor during open circuit condition?
 
magoo said:
It would help if you showed your results so far. This way you can get some feedback.
b?
Also, what is Vd? Did you mean Vb?

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In this workout, I only solved for Z-Thevenin. I was not able to solve for V-Thevenin.

I also meant Id, my apologies, not Vd. In this course, our professors refer to Dependent sources as Vd and Id, and independent sources as Vs, and Is, all labeled 1, 2, and 3 respectively.

scottdave said:
What is the current through the inductor during open circuit condition?

That was the issue, I was not given anything regarding current going through the inductor during open circuit condition. So does this mean that I am only able to solve for Thevenin Impedance?
 

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Also, please forgive me if this is an ignorant question. But isn't the Zth impedance the same as the load resistor between nodes A and B?

If it is, can't I just plug my Z-thevenin impedance back in, complete the circuit, and solve for voltage at inductor? Then I am able to complete finding out current Id of the circuit, and therefore finding the Vth of the circuit.

Thank you!
 
The Thevenin impedance is the equivalent impedance between nodes a and b.

If it is an open circuit, how much current would flow through the inductor?
 
magoo said:
The Thevenin impedance is the equivalent impedance between nodes a and b.

If it is an open circuit, how much current would flow through the inductor?

Wouldn't that be considered a current of 0 going through the inductor?
It's an open circuit, meaning it is infinity resistance, therefore the resistance of air is so high no current is able to complete the circuit. At least that was what I learned in my previous courses.

I will find out the answer tomorrow and report back in case anyone is curious of the results. I just figured I could solve this before class tomorrow morning as good practice.

Thank you!
 
You are correct as far as the current through the inductor. I'm glad that scottdave asked you that question. That means there is no voltage drop across the inductor in this open circuit coindition.
 
The problem for Voc was solved. Thank you for everyones help. VL=0v. Therefore Id=0.25*0, making the Voc equal to 1V=Vth. It was a dumb question, and i knew in my head it was 0V for VL (i just thought it was a trick question somehow).
 

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