Mesh eqs

Discussion in 'Homework Help' started by n_adam, Apr 4, 2014.

  1. n_adam

    Thread Starter New Member

    Mar 1, 2014
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    Hi guys,

    I need to solve this problem with the mesh current method. I am having trouble figuring out the three equations for the three loops. What confuses me is the current source and that the voltage is unknown across it. Any help or hint would be highly appreciated.
     
  2. shteii01

    AAC Fanatic!

    Feb 19, 2010
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    Ok. You did first step. Define the problem.

    Next step is to draw mesh currents. Go do that and post a picture.
     
  3. n_adam

    Thread Starter New Member

    Mar 1, 2014
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    here are the mesh currents
     
  4. n_adam

    Thread Starter New Member

    Mar 1, 2014
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    and the three equations I came up with
     
  5. shteii01

    AAC Fanatic!

    Feb 19, 2010
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    Ok.

    Now. Look at i1. Do you see that i1 enters the current source and exits the current source?
     
  6. n_adam

    Thread Starter New Member

    Mar 1, 2014
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    Yes, so i1 = 0.01A I assume
     
  7. shteii01

    AAC Fanatic!

    Feb 19, 2010
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    Yes. i1=10 mA.

    However. In the future you have to examine these things carefully. Current has magnitude and direction. In your case the magnitude is 10 mA. We assume clockwise direction of i1 means that i1 is positive. So we look at the direction of the current from the current source, it matches the direction of i1. So i1=10 mA.

    However. If direction of current source was opposite of i1, then i1 would have been -10 mA. Meaning that magnitude of i1 is 10 mA, but its assumed direction is wrong which we indicate by the negative sign.
     
  8. n_adam

    Thread Starter New Member

    Mar 1, 2014
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    Ok thank you I got the right answer.
     
  9. n_adam

    Thread Starter New Member

    Mar 1, 2014
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    I have an other problem I can't figure out. I am sure I am really close to the solution but something is not right. Would you mind taking a look at what I have so far?
     
  10. shteii01

    AAC Fanatic!

    Feb 19, 2010
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    Use mesh current. You have 3 meshes. You will have three mesh currents. The current in left mesh and current in center mesh will have to be solved for. The current in the right mesh is going to the be current of the current source, but watch the direction of the mesh current, the mesh current will point down, the current source current points up, that means mesh current will be -28 A.

    Now find the other two mesh currents. Then find the voltages v2 and v3 using Ohm's Law.
     
  11. n_adam

    Thread Starter New Member

    Mar 1, 2014
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    the book specifically asks for node voltage method..
     
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