"Thevenin, Norton, and Maximum Power" worksheet

Discussion in 'Feedback and Suggestions' started by acalhoon, May 14, 2013.

  1. acalhoon

    Thread Starter New Member

    May 14, 2013
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    0
    I've only just gone through a handful of the questions in the "Thevenin's, Norton's, and Maximum Power Transfer Theorems" worksheet (http://www.allaboutcircuits.com/worksheets/thev.html) I'm fairly confident the Thevenin series resistance is incorrect for question 8. The revealed answers show:
    Vth = 8.77 V
    Rth = 210.53 ohm

    Calculations for Thevenin equivalent voltage:
    R1 = 300 ohm
    R2 = 1000 ohm
    R3 = 2000 ohm
    R4 = 400 ohm

    Vth = I2 * R3
    I1(R1 + R2) - I2(R2) = 15
    -I1(R2) + I2(R2 + R3 + R4) = 0

    I1 = 271/14820 A
    I2 = 1/228 A
    Vth = 2000/228 = 8.77V

    Calculations for Thevenin equivalent resistance (Looking in method):
    ((R1 || R2) + R4) || R3 = 479.5 ohm

    Calculations for Thevenin equivalent resistance (Short circuit current method):
    Ith = I2
    I1(R1 + R2) - I2(R2) = 15
    -I1(R2) + I2(R2 + R4) = 0

    I1 = 21/280
    I2 = 3/164

    Rth = Vth/Ith
    Rth = 2000/228*164/3 = 479.5 ohm
     
    Last edited: May 14, 2013
  2. acalhoon

    Thread Starter New Member

    May 14, 2013
    2
    0
    Another issue:

    The "note" associated with the answer for question 11 reads:
    This should read:
     
  3. Georacer

    Moderator

    Nov 25, 2009
    5,142
    1,266
    Thank you, acalhoon.

    I, myself solved the exercise and initially made the same mistake as the author. That is, to first solve for the Thevenin voltage, and then use the same transformed circuit to find the resistance, not noticing that the merged resistances where unusable.

    I would also add, for Question 8, that it should read "Find the Thevenin equivalent circuit" instead of "Thevenize".
     
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