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Homework Help: Find the current

  1. Jul 3, 2017 #1
    1. The problem statement, all variables and given/known data
    the image of circuit is in attachment
    the question is to find the current through the battery

    2. Relevant equations

    3. The attempt at a solution
    I think that there is a y connection
    so above two and centered one form y from formula the whole resistance is 1
    than I imagine bottomed ones and this and above ones as new y type connection and
    I get 1/R = 1/(1/1 + 1/2 + 1/3) and r is equal to 11
    all in all the current should be I=U/R = 3/11
    but in book the answer is 21/19
    please help

    Attached Files:

  2. jcsd
  3. Jul 3, 2017 #2
    you can use delta to y conversion
  4. Jul 3, 2017 #3


    User Avatar

    Staff: Mentor

    Please show the formula used and the details of how you applied it for your Y to Δ transformation. What do you mean by the "whole resistance is 1"?
  5. Jul 3, 2017 #4
    this is the your current equivalent circuit you could change it to the form of
    sorry for my poor drawing skills
  6. Jul 3, 2017 #5
    1/R = 1/(1/r1+1/r2+ 1/r3)
  7. Jul 3, 2017 #6
  8. Jul 3, 2017 #7
    i am sorry i will draw again
    the 3 and 2 are the same old resistors but Ra , Rb , Rc are resistances to be determined using the delta to y conversion hope this clears up
    what i am saying is that this circuit is equivalent to the old circuit if proper values of resistance for a b and c are used
  9. Jul 3, 2017 #8
    i dont understand what formula that is
  10. Jul 3, 2017 #9


    User Avatar
    Homework Helper
    Gold Member

    This is the formula for finding the equivalent resistance of 3 resistors in parallel. Not the delta-wye formula.
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