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Current in the circuit

  1. Jan 31, 2014 #1
    1. The problem statement, all variables and given/known data
    In the given circuit find the current i1,i2,i3.
    (Image of the circuit is attached)

    2. Relevant equations
    current=(emf)/total resistance

    3. The attempt at a solution
    The original question actually asks me to find the currents using Kirchoff's laws .Since I feel this method to be a little tedious I tried to do it another way.
    But the problem is the answers are not coming correct this way ,(which is as follows )

    First since the two cells are connected opposite to each other i have assumed the resultant emf of the 21V to be 4V and I have neglected the other 17V cell.
    then considering 2Ω and 5Ω resistances to be parallel to each other their resultant comes to be
    (10/7)Ω .And this one being in series with 3Ω, The final resistance of the circuit comes out to be
    Accordingly current should be i1=28/31 A
    I am going seriously wrong somewhere:grumpy: , but can't figure out where.:cry: .
    Can you please help?
    Thanks in advance!!

    Attached Files:

    Last edited: Jan 31, 2014
  2. jcsd
  3. Jan 31, 2014 #2
    What you have presumed would have been correct if the two batteries would have been in series .Do you think the batteries are in series ?

    Please be careful ,there is a middle branch between the two batteries.The current flowing through them will not be the same .

    Wrong .

    Wrong .
  4. Feb 2, 2014 #3


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    You'll need to use Kirchhoff's rules here, tedious as they are.

    As Tanya Sharma said, since the two batteries are not actually in series, you can't simply subtract their voltages.
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