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Homework Help: Circuits and Loop Rule

  1. Apr 10, 2010 #1
    1. The problem statement, all variables and given/known data

    Write the loop rule for each of the following circuits:

    2. Relevant equations
    Depending on the loop:
    -emf + IR1 + IR2 + .... + IRn = 0
    V = IR
    If in series: R1 + R2 + ... Rn = R
    If in parallel: 1/R1 + 1/R2 + ... 1/Rn = 1/R

    3. The attempt at a solution

    I really don't know how to do these because we usually only had 1 battery. But here's my shot:

    (A) Could you say that both batteries are in series and treat them as one battery, then say the R2 and R3 are in parallel?

    (B) and (C) I don't have the slightest clue. For (B), I don't know if you can say that R1, R2, and R3 are in series with emf3 there, and (C) we've never had a battery in parallel (We either had 1 battery or 2 batteries in series).
  2. jcsd
  3. Apr 10, 2010 #2


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    Science Advisor
    Homework Helper

    Hi DeadFishFactory! :wink:

    "Loop rule" means that you only consider one loop at a time … that means everything is in one (series) circuit.

    Forget the series and parallel rules … only apply Kirchhoff's rules …

    voltage gain across each battery is the voltage (obviously! :rolleyes:), and voltage drop across each resistor is I times R, and for each loop t all has to add to zero …

    what do you get? :smile:

    (and don't forget to draw the currents in … I1 I2 I3 etc)
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