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Homework Help: Calculating voltage

  1. May 2, 2010 #1
    1. The problem statement, all variables and given/known data
    R1=30Ω R2=20Ω R3=20Ω R4=10Ω R5=40Ω R6=10Ω I4=4A
    I need to calculate U (total voltage)
    schematic:
    http://i43.tinypic.com/2jvbx2.png


    2. Relevant equations



    3. The attempt at a solution
    R23=1/(1/10+1/20)=10ohm
    R234=10+10=20ohm
    R2345=1/(1/R234+1/R5)=1/(1/20+1/40)=13,33ohm
    Rv=R1+R2345+R6=30+13.33+10=53,33ohm
    U=I4*Rv=4*53.33=213,33V

    213,33V is not correct...
     
    Last edited: May 2, 2010
  2. jcsd
  3. May 2, 2010 #2

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    Welcome to PF!

    Hi stefanomm! Welcome to PF! :smile:

    (try using the X2 tag just above the Reply box :wink:)
    No, I4 is the current through R4 only

    you need to find the "overall" current

    (call it I, and find the relation between I and I4). :smile:
     
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