Need help finding node equations

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Discussion Overview

The discussion focuses on finding node equations for a circuit involving node voltages V1 and V3, with an emphasis on leaving resistor R3 as a variable. Participants are examining the equations related to the circuit diagram provided by the original poster.

Discussion Character

  • Homework-related
  • Technical explanation
  • Debate/contested

Main Points Raised

  • The original poster presents a request for help in finding node equations for voltages V1 and V3.
  • One participant encourages the original poster to share their attempts and specific points of confusion to facilitate assistance.
  • The original poster shares two equations they have derived, which they believe pertain to the node voltages.
  • Another participant questions the validity of the equations provided, suggesting that they may not accurately reflect the circuit and challenges the identification of nodes and paths in the equations.
  • Concerns are raised about the paths described in the equations, particularly regarding the connections between nodes and the presence of resistors in the circuit.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus, as there are disagreements regarding the accuracy of the equations and the identification of nodes in the circuit.

Contextual Notes

There are indications of missing assumptions about the circuit configuration, and the equations may depend on the correct identification of nodes and paths, which remains unresolved.

elec_eng
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Need help finding node equations!

[url=http://www.0zz0.com][PLAIN]http://www11.0zz0.com/2012/02/22/06/267083816.jpg[/url][/PLAIN]

I need to find the node equations for node voltages 1 and 3 to find voltages V1 and V3 leaving R3 as a variable!

hope to get help soon!
 
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welcome to pf!

hi elec_eng! welcome to pf! :wink:

show us what you've tried, and where you're stuck, and then we'll know how to help! :smile:

(btw, please don't post such wide pictures!)
 


This is what i tried!
(v1-v4)/R1+ (v1-v3)/R4=0
(v3-v2)/R4+ (v3-v1)/R3+ (v3-v4)/R5= 0
 


elec_eng said:
This is what i tried!
(v1-v4)/R1+ (v1-v3)/R4=0
(v3-v2)/R4+ (v3-v1)/R3+ (v3-v4)/R5= 0

Those equations don't appear to match the circuit. Perhaps you're not correctly identifying everything that comprises the individual nodes? Presumably the first equation is supposed to pertain to NODE 1? If so, what path does the second term describe? Where is the path from NODE 1 to NODE 2?

If the second equation pertains to NODE 3, then the last term is incorrect; it describes a path from NODE 3 to NODE 4 via resistor R5, but this path doesn't exist. Resistor R5 terminates at NODE 0 (Ground).
 

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