Why Do I Get a Negative Value for R2 in My Voltage Divider Circuit?

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Discussion Overview

The discussion revolves around a voltage divider circuit, specifically addressing the issue of obtaining a negative value for resistor R2. Participants explore the circuit configuration, relevant equations, and the implications of resistor values on voltage drops.

Discussion Character

  • Homework-related, Technical explanation, Exploratory

Main Points Raised

  • One participant expresses frustration with consistently obtaining a negative value for R2 and seeks guidance on solving the circuit.
  • Another participant suggests that R1 must be twice the equivalent resistance (Req) to achieve the desired voltage drop across the load, indicating a relationship between R1 and R2.
  • A later post proposes using a Thevenin equivalent to simplify the circuit analysis, suggesting that the output voltage can be evaluated under different load conditions.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on the correct approach to resolve the negative value for R2, and multiple perspectives on circuit analysis methods are presented.

Contextual Notes

There are unresolved assumptions regarding the circuit configuration and the specific values of resistors and voltage sources, which may influence the calculations and outcomes.

Who May Find This Useful

Students and individuals interested in circuit analysis, particularly those working on voltage divider problems or seeking to understand Thevenin equivalents.

Matt1234
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Homework Statement


Hello, can someone please help me create the following curcuit? Id like to know the steps so i can to solve this. I don't seem to be getting the correct answer its very frustrating because it seems so simple. please advise.

[PLAIN]http://img517.imageshack.us/img517/8919/54967623.jpg

Homework Equations



KVL
KCL
Ohms Law


The Attempt at a Solution



Notice i keep getting a negative R2:
Please advise

[PLAIN]http://img404.imageshack.us/img404/5573/lastscanq.jpg
 
Last edited by a moderator:
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After some more review, R1 must be 2 times greater then Req in order to get that drop arrcoss the load. Req being the equivalent resistance of R2 and 1000 ohms.

Now the current being close to 5ma is the next step.
 
Last edited:
anyone please?
 
Suppose you were to replace the 15V supply and R1 and R2 with a Thevenin equivalent. Then you'd have a supply in series with a single resistor.

Now consider the output voltage with 0mA and 5mA loads. If you set them to your +/- 10% conditions, you should have two equations in two unknowns, they being R1 and R2...
 
Last edited:

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