Voltage Divider Circuits - calculation error?

Discussion in 'Feedback and Suggestions' started by zordiac, Sep 29, 2008.

  1. zordiac

    Thread Starter New Member

    Sep 29, 2008
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    0
    In the voltage divider circuits article, there appears to be an error; though, I am a novice, so perhaps I don't understand something?
    http://www.allaboutcircuits.com/vol_1/chpt_6/1.html

    Below this line in the article:
    From here, we can use Ohm's Law (I=E/R) to determine the total current, which we know will be the same as each resistor current, currents being equal in all parts of a series circuit:

    The chart shows 2m as the result of I; however, with other calculators I've used, I get 1m, not 2m. I'm unable to produce 2m no matter what I do. Can someone clarify or correct this issue?

    Thanks very much.
     
  2. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
    5,692
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    Can you show your actual calculation? 45V/22.5k =2mA

    John
     
  3. zordiac

    Thread Starter New Member

    Sep 29, 2008
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    I think I just don't understand how it works... I assumed you should divide the total voltage by the total resistance. From your example, it looks like you're just using the highest resistance in the circuit? Is this how it should be done?

    Thanks.
     
  4. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
    5,692
    901
    22.5k is the total resistance, composed of 5 + 10 + 7.5. The column labeled "total" is not a single resistance, but is a calculation of the sum of the three actual resistors.

    Can you draw and post something to show what you understand the circuit to be -- just to be sure we are talking about the same circuit? John
     
  5. zordiac

    Thread Starter New Member

    Sep 29, 2008
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    John, we're talking about the same circuit. I think this is a result of staying up a little too late. I didn't register that the column was "total" for some reason; though it's plainly obvious now that I look again. Sorry about the misconception.

    Thanks for all your help.
     
  6. jessica

    Guest

    This site is awesome i learned more in this one day, then 2 months in class. Thanks all.
     
  7. Unregistered

    Guest

    I don't understand why there are so many lets say, unhappy comments on this site. I understood the material very well. kVL law and voltage and voltage divider law. It was put very simple and sweet.
     
  8. raybo

    Member

    Oct 18, 2008
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    0
    Is insane to suggest that a potentiometer can be used to obtain lower voltages. well it can provided that the load remains the same and the load is considered in the design. He forget to mention some potentiometers are notlinear but a log function like volume controls. Otherwise reinventing ohms law. but well illustrated. rheostat?
     
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