Why Is Kirchoff's Laws Problem Giving Different Answers?

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SUMMARY

The discussion centers on the challenges faced by a user in applying Kirchoff's Laws to a circuit problem, resulting in inconsistent answers. Key issues identified include the lack of labeling on a resistor, which complicates the analysis, and the importance of showing work to facilitate assistance. A suggested approach involves analyzing voltage loops systematically, starting with the equation for the top half of the circuit. The user is encouraged to clarify the unknown resistor and provide additional loop equations for further guidance.

PREREQUISITES
  • Understanding of Kirchoff's Voltage Law (KVL)
  • Basic circuit analysis techniques
  • Familiarity with resistor labeling and circuit diagrams
  • Ability to formulate equations based on circuit loops
NEXT STEPS
  • Review Kirchoff's Laws with a focus on practical applications
  • Practice circuit analysis using labeled diagrams
  • Learn how to effectively present circuit problems for peer assistance
  • Explore common pitfalls in circuit analysis and how to avoid them
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Students studying electrical engineering, educators teaching circuit analysis, and hobbyists working on electronics projects who seek to improve their understanding of Kirchoff's Laws.

andy s
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Hey guys, I am really struggling with a question on Kirchoff's Laws. I've attempted it 6 times, and each time have got a different answer. Please help.

See attached file.

Thanks in advance :)


p.s Apoligies if I've posted this in the wrong thread, i wasnt sure where to put it so i though "general physics" would be the best.
 

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Just as a pointer for the future, a lot of people probably did not respond because they were afraid that your attachment may have a virus, so if you want to post a picture of something in the future then try and do it as a jpg image (in fact maybe you want to do it now). Macs are immune to most viruses, so I came along. :)

Also the resistor in the bottom left is not labeled, may not have helped your cause. Furthermore, the policy here is to show some of the work you have done so we can tell where you went wrong.

I'll be nice and give you a start. Let's say I want to find the equation for the voltage loop in the top half, going counter-clockwise. I go through and look at all the potential drops, and then add them up such that they are all zero. For example

[tex]-12V + I_1*5 + 9 + (I_3)15 = 0[/tex]

There are two more loops to look at, what did you get for them? Can you tell me what the mysterious resistor is also?
 

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