How can Kirchhoff's Laws be used to solve for current in a circuit?

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    Kcl Kvl Laws
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Discussion Overview

The discussion focuses on applying Kirchhoff's Laws (KVL and KCL) to solve for currents in a circuit. Participants explore the challenges of analyzing a specific circuit configuration and share their approaches to deriving node voltages and branch currents.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Homework-related

Main Points Raised

  • One participant reports difficulty using KVL and KCL, noting that R6 has 0V and 0A, suggesting it may be shorted out.
  • Another participant agrees that R6 is shorted and suggests eliminating it from the circuit diagram, recommending a re-draw for clarity and labeling the voltages at the nodes.
  • A participant expresses uncertainty about identifying patterns in the circuit analysis despite receiving guidance.
  • Further advice is given to label unknown voltages at the nodes and write KCL equations to determine if there are enough equations to solve for the unknowns.
  • Another participant suggests attaching currents to all resistors and naming potentials for nodal analysis, providing specific loop names and current values derived from their analysis.

Areas of Agreement / Disagreement

Participants generally agree on the approach of using KVL and KCL for circuit analysis, but there is no consensus on the specific steps or solutions, as some express confusion and seek clarification.

Contextual Notes

Some participants mention the need for clearer circuit diagrams and the importance of labeling nodes and currents, indicating potential limitations in the initial problem setup.

Who May Find This Useful

This discussion may be useful for students or individuals learning about circuit analysis, particularly those struggling with Kirchhoff's Laws and nodal analysis techniques.

NatsuIgneelFT
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Homework Statement
Use KVL and KCL to determine all voltages and currents through each resistor, and determine current in source.
Relevant Equations
All given is the power source is 5V. All the other elements are resistors (in ohms).
XmB8Rbz.png


I've been trying to use KVL/KCL here but I can't get any. The only thing I accomplished is R6 has 0V, 0A (KVL with its loop). All the other ones I can't get any? Thanks
 
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Welcome to the PF.:smile:

You are correct that R6 is shorted out, so eliminate it from the drawing. You can re-draw it a little more cleanly with the 5V source vertical with its bottom considered a common "ground". When I do that it looks like a bridge circuit, so label the 3 voltages at the 3 nodes (not including ground) and write the KCL equations. Can you show us that work?
 
IMG_20190903_230918.jpg


Thank you. Is this how to do it? I still can't see any patterns here, sorry.
 
Label the unknown voltages on the 3 right nodes and write the KCL equations for them. Then see if you have enough equations to solve for the unknown voltages. Once you have the node voltages, that gives you the branch currents...
 
Kirchoff or nodal.jpg

Attach currents to all resistors -for instance I1 through R1 and so on.

For nodal analyze name X and Y the potentials as per attached sketch.

For Kirchhoff way you have 3 loops:

abdfa, abcefa, abdefa

and two current sum points: d and e

I1=0.03852;I2=0.015485;I3=0.0171638;I4=0.02135755;I5=0.032649
 

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