Thevenin Circuit: Help Me Verify My Solution

  • Context: Engineering 
  • Thread starter Thread starter vikasagartha
  • Start date Start date
  • Tags Tags
    Circuit Thevenin
Click For Summary

Discussion Overview

The discussion revolves around verifying a solution for finding Thevenin equivalents in a circuit. Participants explore the process of identifying load components, calculating Thevenin voltage and resistance, and comparing Thevenin and Norton equivalents. The scope includes homework assistance and conceptual clarification.

Discussion Character

  • Homework-related
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant expresses uncertainty about correctly identifying the load component in the circuit and seeks verification of their solution.
  • Another participant points out that the resistor between terminals A and B is part of the network and should not be removed, indicating a misunderstanding of the circuit's configuration.
  • A participant describes their revised approach, including calculations of currents using a system of equations and finding Thevenin voltage (Vth) but expresses confusion about calculating Thevenin resistance (Rth).
  • One participant suggests checking the sign of a calculated current and provides guidance on finding Rth by suppressing voltage sources and combining resistors.
  • A participant claims to have determined Rth and Vth values and poses a question about the advantages of Thevenin versus Norton equivalents, indicating a desire for deeper understanding.
  • Another participant responds that both equivalents have their advantages depending on the circuit context and suggests that familiarity with both methods is beneficial for problem-solving.

Areas of Agreement / Disagreement

Participants generally agree on the process of finding Thevenin equivalents, but there are varying levels of understanding and some confusion regarding the identification of components and the calculation of Rth. The discussion remains unresolved regarding the best approach to learning Norton equivalents.

Contextual Notes

Participants express uncertainty about specific calculations and the implications of circuit configurations. There is a lack of consensus on the best method for transitioning between Thevenin and Norton equivalents.

vikasagartha
Messages
15
Reaction score
0

Homework Statement


Ive never done Thevenin equivalents before, and I am not sure if I have removed the correct "load component". Could someone please take a look @ my solution and let me know if I have done this correctly? Thanks in advance! I really appreciate it!
Circuit Diagram:
https://www.dropbox.com/s/q5kubgapyu89blt/Screenshot from 2014-09-06 10:15:12.png?dl=0


Homework Equations


V=IR, KCL

The Attempt at a Solution


Written by hand, screenshot attached.
https://www.dropbox.com/s/3u4ku96uvksioul/2014-09-06-101902.jpg?dl=0
https://www.dropbox.com/s/dg1meg27ojsyvtc/2014-09-06-101846.jpg?dl=0
 
Physics news on Phys.org
As drawn the circuit has no load between terminals A and B. A and B is where a load would be attached. The 5 k resistor between A and B is not a load resistor, it is part of the network to be analyzed so don't remove it!
 
  • Like
Likes   Reactions: 1 person
Clearly a conceptual misunderstanding. Makes much more sense now. Thanks for pointing it out:)
 
Second try

New procedure:
1) Left 5k resistor in as A and B have no load in between

2) Used three current loops I1, I2, I3 and calculated three currents using a system of equations.
Current equations
Currents solved
* I1=173.91 micro Amps
* I2= 8.69 micro Amps
* I3= 382.6 micro Amps

3) Found voltage drops over resistors
https://www.dropbox.com/s/xbx05mykzjvjw2y/2014-09-07-061535.jpg?dl=0

4) Used the voltage drops to find the Vth = 826mV
vthevenin

5) Now I am stuck. I have no idea how to find Rth for this circuit! Help!?

PS, sorry the webcam is garbage. My laptop was made ~200 yrs ago;)
 
Check the sign on I2.

To find Rth start by suppressing all the voltage sources, then look for opportunities to combine serial and parallel combinations of resistors. I.e., reduce the circuit. Don't be fooled by the geometrical layout of the drawing --- pay attention to the actual connections of the components by identifying the nodes.
 
thanks for the help gneill. I think I have it figured out. Rth = 1.884k and Vth = 826mV.

I have another conceptual question, if you don't mind. Thevenin vs Norton - I am comfortable with thevenin so I normally find the Vth and Rth and use Vth/Rth = In to then find the norton equivalent. Is there an advantage to one model over the other? Should I bother learning how to find Norton equivalents first?
 
vikasagartha said:
thanks for the help gneill. I think I have it figured out. Rth = 1.884k and Vth = 826mV.
Those values look alright.

I have another conceptual question, if you don't mind. Thevenin vs Norton - I am comfortable with thevenin so I normally find the Vth and Rth and use Vth/Rth = In to then find the norton equivalent. Is there an advantage to one model over the other? Should I bother learning how to find Norton equivalents first?

Both equivalents have their advantages in certain situations. If you're given a circuit that already has current sources, direct reduction to a Norton equivalent may provide a more straightforward approach. Or, perhaps a circuit is just simpler to analyze with mesh equations, where one of the mesh currents is identified with the short circuit current that you're looking for. Then you may only need to find that single mesh current rather than solve for them all (Cramer's Rule rules!).

You should be able to work problems either way if for no other reason than you might be required to demonstrate it on an exam :wink:
 

Similar threads

  • · Replies 4 ·
Replies
4
Views
3K
Replies
3
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 8 ·
Replies
8
Views
3K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 7 ·
Replies
7
Views
3K
  • · Replies 7 ·
Replies
7
Views
4K
  • · Replies 20 ·
Replies
20
Views
12K
Replies
8
Views
3K
Replies
1
Views
2K