Why Does the Maximum Power Transfer Theorem Yield a Negative Resistance?

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Discussion Overview

The discussion revolves around the application of the Maximum Power Transfer Theorem in a circuit involving a 6 ohm resistor. Participants explore the conditions under which the theorem applies, particularly focusing on the calculation of Thevenin equivalent resistance and the implications of obtaining a negative resistance value.

Discussion Character

  • Homework-related
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant describes a scenario where they calculated the Thevenin equivalent resistance across a 6 ohm resistor and found it to be negative, raising a question about the implications of this result.
  • Another participant suggests that understanding the Maximum Power Transfer Theorem is crucial for addressing the issue and asks for a diagram of the circuit to provide better assistance.
  • A further contribution confirms that the circuit consists of an ideal source and other resistances, and mentions the process of finding the Thevenin equivalent resistance.
  • One participant reiterates that maximum power transfer occurs when the load resistance equals the source resistance and prompts the original poster to ensure they have correctly determined the Thevenin equivalent of the circuit.

Areas of Agreement / Disagreement

Participants generally agree on the principle that maximum power transfer occurs when load resistance equals source resistance. However, the discussion remains unresolved regarding the implications of obtaining a negative resistance value in this context.

Contextual Notes

Limitations include the absence of a circuit diagram, which may affect the clarity of the discussion. There is also a lack of consensus on how to interpret the negative resistance result, as well as potential dependencies on the definitions of the components involved.

prashantgolu
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i was solving one question...it said find out value of r in a circuit so that the 6 ohm resistor consumes maximum power...i applied max power theorem ...and calculated the thevenin eqivalent resistance accrss 6 ohm resistance...and put it equal to 6...but the r cam eout to be negative...so wat to conclude from this...
 
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It would help if you posted a diagram of the circuit in question. If this is an ideal source in series with a source resistance and the 6 ohm resistor, then this question is best answered by thinking about the following question:

What is the max power transfer theorem?

I suspect a Mod will be by shortly to move this question, but homework questions like these should be posed in the Homework section:
https://www.physicsforums.com/forumdisplay.php?f=152
 
yes...its just an ideal source...some resistances and a 6 ohm resistance...i just removed it and found out thevenin equivalent across its terminals...and compared it to be 6 for max theorem..i am attaching a file
 

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As you surmise, max power transfer happens when the load resistance is equal to the source resistance. Have you determined the Thevenin equivalent of the circuit connected to the 6 ohm resistor (i.e. everything to the left of that resistor)?
 

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