Calculating Source Voltage and Maximum Power in a Practical Circuit

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Discussion Overview

The discussion revolves around calculating the source voltage and maximum power in a practical circuit involving a voltage source with specified efficiency and load conditions. Participants explore the implications of voltage efficiency, internal resistance, and the relationship between load resistance and power transfer.

Discussion Character

  • Homework-related
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant presents a homework problem involving a practical voltage source with a voltage efficiency of 90% and asks for assistance in determining the source voltage and maximum power.
  • Another participant suggests writing equations for the two load situations to help determine the open-circuit voltage (Vo) and internal resistance (Ri) of the source.
  • A participant questions the meaning of "voltage efficiency," proposing that it might relate to a voltage divider equation, suggesting that 0.9 * Vo could equal the load voltage.
  • There is uncertainty regarding the calculation of internal resistance, with one participant proposing that it could be equal to 1 Ohm based on the efficiency formula.
  • Another participant reiterates the question about the correctness of 1 Ohm as the internal resistance and suggests using a voltage divider equation to find Ri.

Areas of Agreement / Disagreement

Participants express differing views on the concept of "voltage efficiency" and its implications for calculating internal resistance. There is no consensus on the correct interpretation or calculation method for internal resistance.

Contextual Notes

Participants note potential confusion regarding terminology, particularly the use of "voltage efficiency" versus "power efficiency," and the implications for circuit analysis. The discussion reflects varying interpretations of the problem's parameters.

Who May Find This Useful

Students and individuals interested in circuit analysis, particularly those dealing with practical voltage sources and efficiency calculations.

Kobayashi
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Homework Statement


A practical voltage source has a voltage effieciency of 90% when connected to a load of 9 Ohms. When connected to a load of 4 Ohms, the load voltage was 160V. Determine the source voltage and the max power.

Can anyone help me with this question?


Homework Equations


P = (I^2)*(R)


The Attempt at a Solution


I'm not getting the correct answer.
 
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Show us a little more work. A "practical" or real voltage source has an internal resistance (call it Ri) in series with an "ideal" voltage source (that has an open-circuit voltage of Vo). Write the two equations for the two load sitations given, and see if that helps you to determine what Vo is.

And once you know Vo and Ri, do you know how to choose the load resistor value to get the maximum power transfer to it?
 
Hi, if there is a voltage effieciency of 90%: Voltage effieciency = R / R+r

Does this mean the internal resistance is equal to 1 Ohm.
 
I honestly have no idea what "voltage efficiency" is. Is this your translation from another language? There is power efficiency, but efficiency does not pertain to voltage alone.

Maybe they mean that 0.9 * Vo = Vload?
 
Is 1 Ohm incorrect then? How else can internal resistance be calculated in this case? That's the only way I can figure out.
 
Kobayashi said:
Is 1 Ohm incorrect then? How else can internal resistance be calculated in this case? That's the only way I can figure out.

Well if they mean voltage divider instead of voltage efficiency, write the equation for a voltage divider to figure out what Ri is.
 

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