How do I Find Vth With the node voltage method?

Thread Starter

student441

Joined Nov 6, 2021
11
Hello.
I'am practicing circuit analisis about the norton and thevenin's circuits and I can't seem to manage to get the right thevenin's voltage using the node voltage for a)
For the circuit in Fig. 4.111, obtain the Thevenin equivalent as seen from terminals (a) a-b (b) b-c

Captura de ecrã 2022-04-17 204648.png
resolution
1) I did source transformation turning the current source(2A) into a voltage source (10V)
applied node voltage discarding the 1ohm resistance.
I got that Va=18V AND VB=10V
and since vth is in parallel with the 4 ohm resistance then: Vth=(Va-Vb)/4=2 but the solution says that Vth=4
Can you help me get to the desired result.
Your time and attention are deeply appreciated.
Thank you.
 

MrAl

Joined Jun 17, 2014
8,976
Hello.
I'am practicing circuit analisis about the norton and thevenin's circuits and I can't seem to manage to get the right thevenin's voltage using the node voltage for a)
For the circuit in Fig. 4.111, obtain the Thevenin equivalent as seen from terminals (a) a-b (b) b-c

View attachment 265342
resolution
1) I did source transformation turning the current source(2A) into a voltage source (10V)
applied node voltage discarding the 1ohm resistance.
I got that Va=18V AND VB=10V
and since vth is in parallel with the 4 ohm resistance then: Vth=(Va-Vb)/4=2 but the solution says that Vth=4
Can you help me get to the desired result.
Your time and attention are deeply appreciated.
Thank you.


Hello,

How did you get 10v at B ?
DId you remember that when you convert a current source with parallel resistance into a voltage source that voltage source must have a resistance in SERIES with that new voltage source. You also have to know exactly what that series resistor value is which i presume you know or else you have to look that up or ask someone.
Try that and see if you can get the right result this time.
 
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