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Homework Help: Determine the total current in the attached diagram

  1. May 9, 2015 #1
    Hope this is posted in the right place:

    Determine the total current in the attached diagram

    R parallel = 1/9.7 + 1/43 = 0.366^-1 = 2.98ohms
    R series = 4.3 + 7.4 = 11.7ohms
    R total = 2.98+11.7=14.68ohms

    I=V/R
    = 30/14.68
    = 2.04A

    The answer given is 4.67A, what am I doing wrong?

    Thanks,
    Devon
     

    Attached Files:

  2. jcsd
  3. May 9, 2015 #2

    mfb

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    Staff: Mentor

    Where does 7.4 come from and what is in series here?

    If you use a number not given in the problem statement, please explain where it comes from.

    There are more things in parallel.
     
  4. May 10, 2015 #3
    My apologies the 7.4 ohms should be where the second 4.3ohms in series is on the attached sketch. I drew that up late last night.
     
  5. May 10, 2015 #4

    CWatters

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    Hint: There are actually three resistors in parallel.
     
  6. May 10, 2015 #5
    I see only 2?
     
  7. May 10, 2015 #6
    Aha thank you CWatters I see that the 7.4ohm resistor is in fact in parallel.

    Itotal=Vtotal/Rtotal
    Rparallel = 1/9.7 + 1/4.3 + 1/7.4 = 2.12ohms
    Rseries = 4.3ohms
    Rt = 2.12 + 4.3 = 6.42ohms

    It=Vt/Rt
    It = 30/6.42
    It = 4.67A
     
  8. May 11, 2015 #7

    CWatters

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    Looks right to me.
     
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