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Circuit 1

  1. Sep 12, 2004 #1
    hi everyone

    i have a trouble to do this proplem, even i already read the comment hints ,can anyone please help me with this proplem, Thanks for reading

    here is the question : http://www.viethost4u.com/toan/circuit.GIF

    p/s: is the answer 1.2A ?
  2. jcsd
  3. Sep 12, 2004 #2


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    Can you please post what you've tried, tinhnho?
  4. Sep 12, 2004 #3
    the problem is to analyze all equipotential points and join them... also if a resistor is connected between 2 equipotential points then that resistor can disconnected from the circuit for analysis..(because no current flows thru equipotent points)

    the current from the battery, due to symmetry of the circuit divides itself equally into three parts to enter branch 1,2,3
    from the symmetry of the circuit connection we see that points 1,2,3 will have same potential and hence can be connected together.
    similarly points 4,5,6 also have same potential (but not equal to that of 1,2,3)
    therefore at this intermediate stage the equivalent circuit consists of 2 sets of 3 resistors connected in parallel..
    now all that left to do is to connect the remaining(6 resistors) resistors between these to points in parallel
    thus we have 2 sets of 3 resistors in parallel and 1 set of 6 resistors in parallel...
    the net resistance taking all resistors to be 1 ohm is 12
    source voltage is 1 V...therefore current is 1.2A

    The simplified circuit looks like this…forgive me for the crude drawing…that’s the best I could make. http://www.viethost4u.com/toan/pic_c.GIF
  5. Sep 13, 2004 #4


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    It is correct. Good job, tinhnho!
  6. Sep 13, 2004 #5
    i think the current should be -1.2A for final answer right ?
  7. Sep 13, 2004 #6


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    According to my logic, the answer for the question "how much current" is
    1.2 A. For the question about the sign, the answer is "-". But my logic might be different from your teacher's.

  8. Sep 14, 2004 #7
    I think the answer is 1.2A~, but this valure should be negetive, according to the direction of the current. It's just my point.. :redface:
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