Nodal Analysis (KCL): Correct My Equations

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Discussion Overview

The discussion revolves around correcting equations for nodal analysis (KCL) in a specific circuit involving dependent sources. Participants are focused on the accuracy of the equations provided and the implications of the dependent voltage source on the analysis.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant expresses uncertainty about their second equation due to the presence of a dependent voltage source.
  • Another participant asserts that the first and second equations are incorrect, emphasizing that current flows through every element in the circuit.
  • A participant questions whether the equations are at least partially correct, reiterating the confusion caused by the dependent sources.
  • It is noted that the first equation neglects the connection of the controlled voltage source to V3 rather than ground, and the second equation fails to account for current flowing into the V3 node via the 3I2 source.
  • One participant inquires about the expected outcome, specifically whether the goal is to express the three voltages in terms of currents I1 and I2.
  • A participant mentions that they ultimately aim to solve for y-parameters and have previously used mesh analysis, seeking to verify their results through nodal equations.
  • There is a question about whether the y-parameters are needed only for a two-port configuration, suggesting a reduction of the circuit to this form.

Areas of Agreement / Disagreement

Participants generally disagree on the correctness of the initial equations, with some asserting they are wrong while others seek clarification on their partial correctness. The discussion remains unresolved regarding the accurate formulation of the nodal equations.

Contextual Notes

Participants express confusion regarding the impact of dependent sources on the equations. There are indications of missing assumptions related to the circuit configuration and the treatment of dependent sources.

Who May Find This Useful

This discussion may be useful for students and practitioners of electrical engineering, particularly those interested in circuit analysis techniques such as nodal and mesh analysis.

magnifik
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For the following circuit, can someone please correct my equations for nodal analysis (KCL)
9i5w11.png


I am especially unsure about my second equation because of the dependent voltage source to the left of the node.

1) I1 = (V1 - 3I2)/1
2) 0 = V3/2 + (V3 -V2)/2
3) I2 = (V2-V3)/2 + 2V3
 
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(1) and (2) are wrong.

N.B., current flows though every element in the circuit.
 
NascentOxygen said:
(1) and (2) are wrong.

N.B., current flows though every element in the circuit.

the dependent sources are throwing me off. are the equations at least partially correct?
 
magnifik said:
the dependent sources are throwing me off. are the equations at least partially correct?

Your third equation is okay. The first equation is ignoring the fact that the controlled voltage source 3I2 is connected to V3, not ground. The second equation is ignoring any current that may be flowing into the V3 node via the 3I2 source.

What is it you are expected to solve for? Is it the three voltages in terms of currents I1 and I2?

You might find it beneficial to write an equation in terms of the supernode (as indicated by the line breaks):

attachment.php?attachmentid=40509&stc=1&d=1320006593.gif
 

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gneill said:
Your third equation is okay. The first equation is ignoring the fact that the controlled voltage source 3I2 is connected to V3, not ground. The second equation is ignoring any current that may be flowing into the V3 node via the 3I2 source.

What is it you are expected to solve for? Is it the three voltages in terms of currents I1 and I2?

ultimately, i will be solving for y-param. i was able to do so using mesh analysis instead, but i was hoping to try and obtain the nodal equations to double check my answers.
 
magnifik said:
ultimately, i will be solving for y-param. i was able to do so using mesh analysis instead, but i was hoping to try and obtain the nodal equations to double check my answers.

Are you wanting the Y parameters only for the two-port? That is, just for V1-I1 as the input and V2-I2 as the output, in effect reducing the whole circuit to just a two-port?
 

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