Analyze this circuit with 2 sources and 4 resistors

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Discussion Overview

The discussion revolves around analyzing a circuit with two sources and four resistors, focusing on current flow, the meaning of a dependent source, and the configuration of resistors. Participants are exploring the application of nodal analysis and Kirchhoff's laws to understand the circuit's behavior.

Discussion Character

  • Exploratory
  • Technical explanation
  • Homework-related
  • Debate/contested

Main Points Raised

  • One participant questions how current flows in the circuit and the actual path it takes, regardless of the diagram's directions.
  • Another participant explains that the "5i" above the dependent source represents a voltage dependent on the current through a specific resistor.
  • There is a request for clarification on whether two resistors are in series or parallel.
  • Some participants emphasize the need for the original poster (OP) to show their work and attempt to set up Kirchhoff's Current Law (KCL) equations.
  • Multiple participants discuss the independence of equations needed for a unique solution, with some suggesting that the proposed equations may not be independent.
  • There are differing opinions on the role of the 6-ohm resistor, with some stating it has no effect on the circuit's analysis.
  • Participants express the need for clearer definitions of currents at each node and the implications of dependent sources on the analysis.
  • Several participants engage in clarifying the relationship between voltages and currents in the context of the circuit analysis.

Areas of Agreement / Disagreement

Participants do not reach a consensus on several points, including the independence of equations, the role of the 6-ohm resistor, and the correct interpretation of the dependent source. The discussion remains unresolved with multiple competing views.

Contextual Notes

Participants highlight the importance of defining nodes and currents clearly, as well as the need for independent equations in circuit analysis. There are references to potential communication issues regarding the definitions and roles of various components in the circuit.

  • #31
mkamalzayed said:
Depending on your assumptions
Node v2 does not receive any current
How do I apply the KCL law?
v2 receives i2, i4, i5.
 
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  • #33
mkamalzayed said:
Where????
These currents flows out of v2
View attachment 353471
Look at the diagram in post #15. i2, i4 and i5 are shown.
 
  • #34
i2,i4,i5 flows from v2
There are not currents entering the node v2
 
  • #35
mkamalzayed said:
i2,i4,i5 flows from v2
There are not currents entering the node v2
You are forgetting what BvU said in post #15: "No worries about the directions of the currents: the correct sign will come out in the analysis."

The arrows on the diagram may not be showing the direction of physical current flow. What if i2 has a negative value?
 
  • #36
Proceed like this. First note that the 6 ohm resistor is connected across voltage sources so it has no effect on the values of v1, v2 and v3; remove it--that means i6=0.

Treating v1, v2 and v3 as a supernode means that you don't write 3 KCL equations for each of v1, v2 and v3. Instead you write one KCL equation for the supernode (the supernode being the combination of v1, v2 and v3). That equation expresses the fact that the sum of the currents entering or leaving the supernode sum to zero.

If i6=0, then i=i4 and i3=i5 so the 3 currents i, i2 and i3 are the only currents entering or leaving the supernode. So we have i+i2+i3=0. Can you express that equation using v1,v2,v3 and the values of the 3 resistors?

To finish you'll need two constraint eqations; I'll help you with those.
 
  • #37
mkamalzayed said:
How ?? "5i" is a current not a voltage
BvU said:
The diamond
1730723722591.png
represents a dependent voltage source of 5i Volts, where i is the current through the 2Ω resistor (
1730723903277.png
in the diagram).


You have chosen not to answer any of the questions asked in #14, so why should I bother to answer
mkamalzayed said:
Depending on your assumptions
Node v2 does not receive any current
How do I apply the KCL law?
Before diving into supernodes, you should first come to understand the diagram and why KCL says ##\ \ i_2+i_4+i_5=0\ \ ## (or ##-i_2-i_4-i_5=0##, which is equivalent).



##\ ##
 
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  • #38
The OP is on a 10-day vacation from PF for several issues, so I'll go ahead and close this thread for now. It may be reopened after the OP is back if they send me a PM and show me what they understand about this circuit analysis. Thank you to all who have been patiently trying to help this user in this thread.
 

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