Confirmation with exercises on thévenin (part two)

Discussion in 'Homework Help' started by jorgemotalmeida, Jun 3, 2008.

  1. jorgemotalmeida

    Thread Starter Member

    Oct 23, 2007
    23
    2
    Hi


    This one... I've tried to use mesh analysis... but it seems more tricky... please tell me what I'm doing wrong in this exercise.


    I attached 3 files. See first the exercise1_1part.jpg, then exercise1_2part.jpg, and finally the file named as quizz22.jpg

    Please see the quizz22 and tell me how comes the value V Thev = (60) (60) / 80 ... in the other 2 files, the doubts are identified.

    Thanks.
     
  2. jorgemotalmeida

    Thread Starter Member

    Oct 23, 2007
    23
    2
    I forgot to put the first file. Here goes...
     
  3. jorgemotalmeida

    Thread Starter Member

    Oct 23, 2007
    23
    2
    I realized why I mistaked on mesh analysis... because really i2-i1= 1,5 A and not i2=1,5 A. we have a super mesh! :D I will make it again. :)

    Please see now only the other doubts. Thanks.

    edit:

    Is it right? >>>

    Mesh 1 and Mesh 2:

    60 i2 + 20 i2 + 30 (i2 - i3) + 10 (i1 - i3) + 40 i1 = 0

    Mesh 3:
    -30 + 10 (i3 - i1) + 30 (i3 - i2) = 0

    Mesh 3 + Mesh 2 : i2 - i1 = 0

    Then it appears like this:

    50 i1 + 110 i2 - 40 i3 = 0
    -10 i1 - 30 i2 + 40 i3 = 30
    -i1 + i2 = 1

    resolving the system give us .... i1 = -0.417 A and i2 = 0.5833 A...

    If our V(A) is V = R I == V = (60+20) * i2 == V = 80 * 0.5833 and it gives 46,64 V....

    NOT so precise as nodal analysis.. (it gave 45 V)
     
    Last edited: Jun 3, 2008
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