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mesh analysis PROBLEM

Discussion in 'General Electronics Discussion' started by djengala, Feb 4, 2016.

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  1. djengala

    djengala

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    Feb 4, 2016
    hi all im new in electronics and las week i had an exam and a question on the exam was how many meshes are in this circuit http://puu.sh/mUbFA/98ed6b8ad1.png really basic meshes no super meshes or somthinng like that

    please help because i think the teacher is wrong thanks in advance
     
  2. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
    What was his answer, you didn't say.
    Adam
     
  3. djengala

    djengala

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    Feb 4, 2016
    his answer was 13 mesh but i think its 4
     
  4. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
    I would have said 4 also. But there must be a reason he said 13?
    Adam
     
  5. djengala

    djengala

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    Feb 4, 2016
    HERE are the 13 meshes he took [​IMG]
     
  6. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
    Well yeah but to work it out I dont think you need all 13. I know a guy that will know all this @Ratch, care to comment?
     
  7. Ratch

    Ratch

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    Mar 10, 2013
    Depending on the definition of a mesh, I would think that if you can write a KVL equation on it, it is a mesh. For instance, using the above numbering, and selecting loops #9, #5, and #7, one could solve for all the voltages and currents. That is because those three loops cover all the resistors and voltage source. There are other combinations that also cover all the circuit elements.

    Ratch
     
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  8. djengala

    djengala

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    Feb 4, 2016
    isnt it a single loop ?
     
  9. Ratch

    Ratch

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    Mar 10, 2013
    Isn't what a single loop?

    Ratch
     
  10. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    Of course you can draw 13 meshes as shown in post #5. This is what the exam asked for, therefore the teacher's answer is correct.
    This kind of "test" is a common entertainment.

    It is, however, not necessary to identify these 13 meshes and set up the equations for them to solve the circuit, see post #7 by Ratch. This is where you have gotten confused during the exam. In any test, not specifically an electronics exam, it is essential to carefully read and understand the task before answering.
     
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  11. djengala

    djengala

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    Feb 4, 2016
    well this kinda sucks because if there is no point in identifying the other meshes then why bother
    anyways thanks for all your answers
     
    Last edited: Feb 6, 2016
  12. dorke

    dorke

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    Jun 20, 2015
    Well,
    your teacher is correct.

    The definition of a Mesh(in planar circuits) is:
    A loop which does not enclose any other loops.
    That number here is indeed 13 as shown.

    A different question is what is the minimal number of mesh equations needed to "solve" this circuit.
    That number here is 1!
    Hint:
    That circuit can be easily "degraded" to a single mesh (#1) by parallel and serial equivalents of most resistors in it...;)
     
    Last edited: Feb 7, 2016
    Arouse1973 likes this.
  13. djengala

    djengala

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    Feb 4, 2016
    thank you for the explanation
     
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