Solving 0th-Order Circuit Equations with Two Variables

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Discussion Overview

The discussion revolves around solving 0th-order circuit equations involving two variables, specifically focusing on the equations derived from a circuit diagram. Participants are attempting to find the correct values for the voltages v1 and v2 based on their circuit analysis and simulations.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant presents two equations derived from a circuit analysis but struggles with the signs and current directions.
  • Another participant suggests a different approach to writing the equations, emphasizing that the sum of currents out of a node should equal zero.
  • A later reply indicates a breakthrough in understanding, providing corrected equations and voltage values for v1 and v2.
  • Another participant questions the validity of the calculated value for v2, asserting that it should be less than the voltage of the right-side source (320V).
  • A subsequent post corrects a previous typo regarding the value of v2, stating it should be 200V, which matches results from Mathematica and multisim.

Areas of Agreement / Disagreement

Participants express differing views on the correctness of the voltage values, particularly for v2, and there is no consensus on the final values or the approach to solving the equations.

Contextual Notes

Participants mention issues with signs and current directions, indicating potential misunderstandings or misapplications of circuit analysis principles. The discussion includes corrections and refinements of earlier claims without resolving the overall problem.

Who May Find This Useful

Students or individuals interested in circuit analysis, particularly those working on similar homework problems or seeking to understand the nuances of setting up circuit equations.

pat666
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Homework Statement



see attached

Homework Equations


The Attempt at a Solution



[tex]0=(v_1-128)/5-V_1/60-(v_2-V_1)/4[/tex]
[tex]0=(v_2-v_1)/4-v_2/80-(v_2-320)/10[/tex]
I obviously know what the answer should be from multisim but its not coming out. I've tried multiple combinations of this mainly just changing -s to +s because I can never get the current direction right for some reson.

Thanks

edit: the covered up resistor is a 10ohm
 

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pat666 said:

Homework Statement



see attached

Homework Equations





The Attempt at a Solution



[tex]0=(v_1-128)/5-V_1/60-(v_2-V_1)/4[/tex]
[tex]0=(v_2-v_1)/4-v_2/80-(v_2-320)/10[/tex]
I obviously know what the answer should be from multisim but its not coming out. I've tried multiple combinations of this mainly just changing -s to +s because I can never get the current direction right for some reson.

Thanks

edit: the covered up resistor is a 10ohm

Yeah, your signs are kind of strange. I just write the sum of the currents out of a node is equal to zero. Don't do subtractions or whatever you are doing.

So your first equation should be:

(v1-V1)/5 + v1/60 + (v1-v2)/4 = 0

Write out both equations using this form, and see if it all solves up better...
 
Yeah, I had an epiphany last night and started getting these right:)
(v1-128)/5 + v1/60 + (v1-v2)/4 = 0
(v2-V1)/4+v2/80+(v2-320)/10=0

v1=162
v2=320
 
pat666 said:
Yeah, I had an epiphany last night and started getting these right:)
(v1-128)/5 + v1/60 + (v1-v2)/4 = 0
(v2-V1)/4+v2/80+(v2-320)/10=0

v1=162
v2=320

v2 looks wrong. V2 = 320V is the right side source, so v2 has to be less than 320V...
 
oops that's a typo v2 cane out as 200V, I put it in Mathematica and it matched multisim so i assumed that I was correct.
 

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