Beginner Circuitry Analysis - Assistance Appreciated =)

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Discussion Overview

The discussion revolves around analyzing a circuit with two current sources using mesh-current and nodal-voltage analysis. Participants explore the setup of equations and the application of circuit analysis techniques, particularly focusing on the challenges of incorporating multiple current sources.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant expresses difficulty in applying mesh-current analysis with two current sources, noting confusion about voltage differences across current sources.
  • Another participant suggests that the initial approach complicates the problem by introducing unnecessary variables and recommends using KCL instead.
  • A third participant proposes that only nodal analysis is needed, indicating that mesh analysis may not be necessary.
  • A later reply presents a set of nodal equations and claims to have solved for voltages Va and Vb, suggesting that the results satisfy KCL and KVL.
  • One participant affirms the correctness of the method used without verifying the arithmetic.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the best approach to the problem, with differing opinions on the necessity of mesh versus nodal analysis. The discussion remains unresolved regarding the correctness of the arithmetic in the final solution.

Contextual Notes

Some participants point out potential issues with variable definitions and the complexity introduced by additional currents, but these concerns are not fully resolved. The discussion reflects varying levels of familiarity with circuit analysis techniques.

slh3410
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I'm given that i1=5.4A and i2=1.5A. I know that I need to apply mesh-current and then nodal-voltage analysis, but I have never dealt with two current sources. It seems like however I set it up, I am missing a piece.

My first attempt at a KVL equation using mesh analysis incorrectly established that the voltage differences V1 and V2 both had to be zero. Unless there is a voltage difference over a current source, I do not know where to start a correct solution.

Here was my first set of equations in full, with my currents numbered 1-4, left to right, in the clockwise direction.

KVL 1) (i1-i2)(40)=0
KVL 2) (i2-i1)(40)+(i2)(80)+(i2-i3)(80)=0
KVL 3) (i3-i2)(80)+(i3-i4)(120)=0
KVL 4) (i4-i3)(120)=0
 
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current source #1 is defined as i1
current source #2 is defined as i2

you redefined i2 as i4. in the future it would be better practice to call the current from left to right i1,i3,i4,i2...

now that being said you are making this very difficult to solve. by adding the currents i3 and i4, you are adding extra variables to solve.

If i were you, I would writ 2 KCls, then use the resulting equations to solve for v1 and v2
 
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You won't need mesh and nodal, just use nodal
 
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Am I on the right track now? I took the 'just use nodal-voltage analysis' advice.

pEFlLfE.jpg


For Va) [(Va-Vb)/8]+[Va/40]-[5.4]=0
For Vb) [(Vb-Va)/8]+[Vb/80]+[Vb/120]+[1.5]=0

Solving that, Va=96V and Vb=72V

Solving for V1 and V2 in the original problem, I again get V1=96V and V2=72V. This seems right to me. The final circuit satisfies KCL and KVL for all loops and nodes. Can somebody please verify for me?
 
Last edited:
Your method is correct!

I did not check the arithmetic.
 
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Alright, I'll double check the arithmetic because that is certainly not your job :)

Thank you to everyone.
 

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