KCl and KVL

Discussion in 'Homework Help' started by tanzer1234, Oct 22, 2010.

  1. tanzer1234

    Thread Starter New Member

    Oct 22, 2010
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    i have tried many current assumptions with the problem hower each time i solve the two kvl equations i get different values for current and voltage please help.
    i did kvl in the two bottom right and left loops and used the fact that delta v=500 *i1 wer i is assumed current
     
  2. The Electrician

    AAC Fanatic!

    Oct 9, 2007
    2,282
    326
    It sounds like you're on the right track, but to help you I would need to see more details of your work.

    In order to efficiently help, it would be good if we used the same set of unknown currents and voltages.

    I've attached an picture of your circuit with unknown currents and voltages designated.

    If you would show your equations using those unknowns, I can help you see where you are going wrong.
     
  3. tanzer1234

    Thread Starter New Member

    Oct 22, 2010
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    0
    and then i solve the final two simultaneous ,is there anything wrong till here?
     
  4. tanzer1234

    Thread Starter New Member

    Oct 22, 2010
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    0
    any idea whats wrong
     
  5. tanzer1234

    Thread Starter New Member

    Oct 22, 2010
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    0
    i got that i0=0.152A
    i1=0.112A
    v delta =56v
     
  6. The Electrician

    AAC Fanatic!

    Oct 9, 2007
    2,282
    326
    You haven't shown me the equations that preceded the last two, so I can't really help. You probably have an inconsistent set of equations. You need the powers absorbed or delivered by all 4 sources, so you need to completely solve the network; you need ALL the currents and voltages.

    Using the mesh method, you can solve the network, using the currents and voltages in the image I attached to post #2. You will need 4 equations in 4 unknown. The mesh method works best when all the sources are voltage sources, but you also have two current sources, so some of your equations won't be KVL equations, but will be constraint equations.

    What I would do is to write two KVL equations for the I1 loop and the I3 loop, then two more constraint equations.

    KVL equations:

    Eq 1: 100*(I1) + 250*(I1 - I2) = 20
    Eq 2: 500*(I3 - I2) + 200*(I3) = .4*250*(I1-I2)

    and two constraint equations:

    Eq 3: I4 - I2 = .2
    Eq 4: I4 = .003*500*(I2-I3)

    Can you solve these 4 simultaneous equations?

    After you do, you will know all the currents and voltages across the 4 sources, and then you can calculate the various powers.

    Try it, and see what you get.
     
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