Thevenin equivalent circuit parameters

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Discussion Overview

The discussion revolves around determining the Thevenin equivalent circuit parameters, specifically VTh and RTh, for a given circuit. Participants are addressing the conversion of a current source to a voltage source and the subsequent steps required to analyze the circuit.

Discussion Character

  • Homework-related
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant questions the proper method for converting a current source to a voltage source, expressing confusion about the polarity involved in this process.
  • Another participant confirms the initial conversion step and provides a visualization of the current flow through the circuit, suggesting that the voltage source should be oriented with its positive terminal pointing upwards.
  • A different participant asserts that the polarity of the voltage source in the subsequent figure should be reversed and notes that further steps are needed to simplify the circuit using a voltage divider.
  • Another contribution reiterates the conversion of the current source to a voltage source, specifying the resulting voltage and instructing to redraw the circuit with the resistor in series with the voltage supply.

Areas of Agreement / Disagreement

There is no consensus on the correct polarity of the voltage source, as one participant suggests it should be reversed while others support the original orientation. Additionally, the discussion remains unresolved regarding the complete steps needed to finalize the Thevenin equivalent parameters.

Contextual Notes

Participants express uncertainty about the conversion process and the implications of polarity, indicating that assumptions about the circuit configuration may affect their conclusions. The discussion also highlights the need for further simplification of the circuit using a voltage divider.

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Homework Statement


https://www.physicsforums.com/attachment.php?attachmentid=32837&stc=1&d=1299373667

Determine the Thevenin equivalent circuit parameters, VTh and RTh, referred to terminals A and B of the circuit shown below?

Homework Equations





The Attempt at a Solution



My only question is this step:
https://www.physicsforums.com/attachment.php?attachmentid=32838&stc=1&d=1299373667
Converted current source to voltage source (V = IR = 10 x 2 = 20 V), then combined the 10 ohm and 5 ohm resistor.

I'm pretty sure I've just ignored the polarity of the current source to get here - I've always been confused as to what to do with converting sources and polarity. Is this correct? If not, what is the proper way to convert the current source to a voltage source (assuming that is the correct method to solve the problem)?

Thanks!
 

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ya, that looks right. Just think that the 2 amps is making a loop through the 10 ohm resistor. If you made a circle on the left loop with an arrow pointing in the same direction as the current source. The current would go up through the 10 ohm resistor. So put your voltage source so the + side is pointing up.
 


1. The polarity of the voltage source in the second figure should be reversed.
2. You're not done yet. You've still got to resolve the 15Ω/5Ω voltage divider into a single resistance and voltage source.
 


Change your current source into a voltage source, which should give you a 20V voltage source. When you redraw the circuit, put the resistor in series with the voltage supply and that will give you the voltage divider that gneill was referring to.
 

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