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Efficiency - how to get the maximum efficiency in a circuit?

  1. Mar 3, 2014 #1
    efficiency -- how to get the maximum efficiency in a circuit?

    1. The problem statement, all variables and given/known data

    I don't quite understand how to get the maximum efficiency in a circuit.

    Exemple.

    4 Volts and 2.0Ω will produce 8 watts with a current of 2.0 amps.
    5 Volts and 3.1Ω will produce 8 watts with a current of 1.6 amps.

    There are infinitely ways to do so. Also we have an led which has to be connected.



    2. Relevant equations
    P=UI=I^2*R=U^2/R


    3. The attempt at a solution
    My intuition says that the first one is more efficient, but the battery will drain faster. I realy want to know how to mix this information together for my circuit.
     
  2. jcsd
  3. Mar 3, 2014 #2

    BvU

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    Hello Lex,
    What is the question ? How to most efficiently do what exactly ?
     
  4. Mar 3, 2014 #3

    CWatters

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    More details are required.

    Both are 100% efficient if the wanted output is heat.

    Both are 0% efficient if the wanted output is light (because there is no light bulb or LED in the circuit as described so far).
     
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