# "Thevenin, Norton, and Maximum Power" worksheet

#### acalhoon

Joined May 14, 2013
2
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

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#### acalhoon

Joined May 14, 2013
2
Another issue:

"Let students know that there really is such a thing as a perfect current source, just as there is no such thing as a perfect voltage source. However, there are devices the closely approximate ideal current sources (current transformers in AC circuits and "current mirror" DC transistor circuits, for example)."