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Design a Circuit

  1. Jul 29, 2014 #1

    Zondrina

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    Homework Helper

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

    You are given two ideal batteries with ##\epsilon_1 = 1.5 V## and ##\epsilon_2 = 9.0 V##. You are also given three ##120 \Omega## resistors.You may use any or all of the components. Design a circuit where there is a current of ##21 \pm 1 mA## through at least one of the resistors.

    Do NOT use EMF sources in parallel.

    2. Relevant equations



    3. The attempt at a solution

    I've already tried several combinations of resistors and batteries with no avail. The closest I've been is when all three resistors are in series with the ##9.0 V## emf. Then the current across the whole circuit is ##25 mA##. I've also tried creating several multiloop circuits, but those haven't worked either.

    Anyone have some design advice? It would be very appreciated.

    EDIT: Never mind guys I got it, just place the resistors in series and then oppose the emfs. Then the current is ##\frac{9.0-1.5}{360} = 21 mA##.
     
    Last edited: Jul 29, 2014
  2. jcsd
  3. Jul 29, 2014 #2

    phinds

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    2016 Award

    glad to see you got it. I've never understood the utility of such problems, they just seem silly to me but I've seen them before.
     
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