Finding Mesh Currents

Discussion in 'General Electronics Chat' started by Navito, Sep 12, 2012.

  1. Navito

    Thread Starter New Member

    Sep 12, 2012
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  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    I3= 4mA
    so 4ma *1k= 4volts dropped across the first 1K resistor leaving 2Volts across the 3 parallel resistors.

    6V-4v= 2Volts across the 3 parallel resistors( 2k/2k/1k) = 2v/0.5k = 4ma

    I1=2mA, so 4mA-I1=2mA, so I0+I2= 2mA

    as they are both 2K each the current is split equally

    1mA in each, so I0=1mA and I2=1mA
     
    Last edited: Sep 12, 2012
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  3. lizard

    New Member

    Sep 10, 2012
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    SO simply explained..................by senior.
     
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  4. Navito

    Thread Starter New Member

    Sep 12, 2012
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    Thanks Dodgydave, great explanation!!
     
  5. bretm

    Member

    Feb 6, 2012
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    That doesn't look right. The 4mA is a superposition of i3 and i2. So the top 1k doesn't have 4mA and doesn't drop 4V.
     
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  6. bretm

    Member

    Feb 6, 2012
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    Let's call the top resistor R1 and it drops V1, the left-most resistor R2 and it drops V2, the bottom-center resistor R3 and it drops V3, and the bottom-right resistor is R4 and drops V4.

    From inspection we know V1 / 1000ohm = i3

    We know that i1 = 2mA, so we can see V2 / 1000ohm = 2mA - i3.

    On the right-hand side we can see V3 / 2000ohm = -2mA - i3

    From the center node we can see V4 / 2000ohm = 4mA + i3

    So all four voltages are in terms of i3. What value of i3 is correct? We know that V1 - V2 - V3 + V4 have to add up to -6V (look for the path). The only value that makes this work is i3 = -(2/3) mA.

    Since 4mA = i2 - i3, we have i2 = (10/3) mA.

    That means i0 = -(4/3) mA.
     
    Last edited: Sep 12, 2012
  7. Dodgydave

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    Jun 22, 2012
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    There must be MINIMUM of 4mA through the 1K resisitor at the top, as that is the highest current flowing in the circuit! ( the circuit wont work as its just theory)
     
  8. t_n_k

    AAC Fanatic!

    Mar 6, 2009
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    Hi there - bretm is correct. Io is -4/3 mA.
     
  9. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    It sounds like you have made a conclusion before you made an analysis. I've run the numbers and arrived at the same answer as bretm did (he beat me to posting it so I did not bother).
     
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