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

AI Thread Summary
The discussion revolves around troubleshooting a voltage divider circuit where the user is confused about obtaining a negative value for R2. They express frustration with the simplicity of the problem and seek guidance on solving it. Key points include the need to ensure R1 is twice the equivalent resistance (Req) to achieve the desired voltage drop across the load. The user also mentions calculating current close to 5mA and suggests using a Thevenin equivalent for simplification. The conversation emphasizes the importance of setting up equations based on load conditions to find R1 and R2 accurately.
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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