Circuit with switch.

Discussion in 'Homework Help' started by cdummie, Sep 18, 2015.

  1. cdummie

    Thread Starter Member

    Feb 6, 2015
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    When the switch in the circuit is closed, then I=(3-j)A. Find complex power of Ig1 when the switch is off if we know that then, complex power of Ig2 is Sig2=(10+j6)VA.

    Known values are: Z=(2-j2)Ohms , Z1=(1+j2)Ohms, Z2=Z4=(2+j4)Ohms, Z3=(2-j4)Ohms, Ig1=(0.5+j1.5)A and E=(7+j3.5)V.

    kolo.jpg

    In the first case, there's no impedance Z in the circuit, does it means that there's no Ig2 in the circuit since both ends of Ig2 are on the same potential or i'm wrong, i am not really sure about this because that would mean that Ig2 is zero and how then it's complex power can be (10+j6)VA?
     
    RRITESH KAKKAR likes this.
  2. WBahn

    Moderator

    Mar 31, 2012
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    Think about this for just a moment.

    Ig2 is a constant current source. By definition, whatever current it put out yesterday it is putting out today and it will put out tomorrow.
     
  3. cdummie

    Thread Starter Member

    Feb 6, 2015
    104
    1
    So how should i approach this, any hints?
     
  4. shteii01

    AAC Fanatic!

    Feb 19, 2010
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    Mesh-Current Method or Node-Voltage Method, you pick one.
     
  5. cdummie

    Thread Starter Member

    Feb 6, 2015
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    I though about that, but i don't know the values of E2, E3 and Ig2.
     
  6. shteii01

    AAC Fanatic!

    Feb 19, 2010
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    You know power at Ig2 when switch is Off. So you can probably figure out Ig2.

    E2 and E3... yeah, I would need to get some equations going to figure out if finding their values is possible.
    I notice that you are not doing it, therefore I don't see any reason why I should.
     
  7. cdummie

    Thread Starter Member

    Feb 6, 2015
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    I understand, but i think that this could be solved using theorems, doing it with methods could take way too much time and it could be useless, so i thought about theorems, but i couldn't figure out which one would be good. Anyway, i will try to use the power of Ig2 somehow in second case, as you mentioned, so thanks for advice.
     
  8. Russmax

    Member

    Sep 3, 2015
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    This is a methods problem, not a theorems problem. You have to do a fair amount of algebra here.
     
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