Why do I get different answers with different methods - Thevenin

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Discussion Overview

The discussion revolves around determining the Thevenin equivalent of a given circuit, with participants exploring different methods and approaches to arrive at the solution. The focus includes theoretical understanding and practical application of Thevenin's theorem.

Discussion Character

  • Homework-related
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant presents a circuit and mentions using three different approaches to find the Thevenin equivalent, expressing uncertainty about which method is correct.
  • Another participant requests detailed steps of the methods used to clarify the reasoning behind the different results.
  • A later reply suggests that one of the attempts is correct, stating a specific value for the Thevenin voltage (Uth = 5V) and providing a value for the Thevenin resistance (Rth = 5500 Ohms).
  • There is a challenge regarding the first method, where it is pointed out that the participant may have incorrectly calculated a current by shorting the output instead of determining the open circuit voltage.

Areas of Agreement / Disagreement

Participants express differing views on the correctness of the various methods used to determine the Thevenin equivalent, and there is no consensus on which approach is definitively correct.

Contextual Notes

Participants have not provided complete details on the assumptions or definitions used in their calculations, and there are unresolved steps in the mathematical reasoning behind the different methods.

Yealtas

Homework Statement


Determine the Thevenin equivalent of the following circuit:
https://imgur.com/a/74UjA (Top image)

upload_2017-12-18_9-53-13.png


Homework Equations


-

The Attempt at a Solution


The last 3 images in the Imgur album are all different approaches.

I can't figure out what the right one is, and why the other ones are wrong. I spent hours searching on google, and I feel like I understand Thevenin/Norton well -now I am not so sure..-, but to no avail.

Extra information:
- Ub = Usource
- "zal door Rv gaan" means "will pas through Rv"

EDIT: I think my second attempt is correct. Uth = 5V. The 1st and 3rd method are presumambly wrong. I sort of have an idea of why, but I am still not 100% convinced.
 

Attachments

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Can you write down the steps you are taking eg...

1) Remove load resistors (none to remove in this case)
2) Replace current sources with..

etc
 
Hi Yealtas,

Please upload your images and embed them in your posts as local attachments. You can use the UPLOAD button at the bottom right of the edit window.

We find that off-site stored images and documents have a tendency to "evaporate" over time, rendering their threads here nearly worthless to members who come across them in the future.

Thanks.
 
Last edited:
Yealtas said:
EDIT: I think my second attempt is correct. Uth = 5V.

Yes and Rth = 5500 Ohms.

Re: First image/attempt: You appear to be shorting the output to calculate I5 when you should be calculating the open circuit voltage (so I5 = 0).
 

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