Thevenin Equivalent with a dependent source

[RedDead]

Find the Thevenin Equivalent circuit between A and B
the circuit is in the attachments...
i don't know how to start
and what is the difference if A and B were for e.g after the 6V source?

thanks

[Jony130]

To find Thevenin's equivalent at terminals a & b you need to find

1. The open circuit voltage Vab = Vth.
2. The current flowing from a to b when a & b are shorted together.
3. Hence find Rth = Vab(open circuit)/Iab(short circuit)

[RedDead]

Originally Posted by Jony130

To find Thevenin's equivalent at terminals a & b you need to find

1. The open circuit voltage Vab = Vth.
2. The current flowing from a to b when a & b are shorted together.
3. Hence find Rth = Vab(open circuit)/Iab(short circuit)

i know that, but i am confused about how to start because there is a dependent source.
how can i find Vx?

[Jony130]

Well first you need to find Vth voltages
So diagram look like this



Vth = - V1 * R2/ (R2+R3) = -3.2V

And now we need to find Isc



So I write nodal equation

(Va - (-8V) )/3Ω = (0V-Va)/1Ω + ( (-5•Va) - Va )/2Ω

So the only think you need to do, is to find voltage at Va node.

[RedDead]

thank you, you are brilliant

[RedDead]

Originally Posted by Jony130

Well first you need to find Vth voltages

but where is the 4 ohm resistor which is parallel to the 8 volt source?

[Jony130]

Well I remove this resistor becaues it is connect parallel to the voltage source.
So this resistor has no effect on Va voltages.

[RedDead]

Originally Posted by Jony130

Well I remove this resistor becaues it is connect parallel to the voltage source.
So this resistor has no effect on Va voltages.

ah, i get it now
thanks again
you saved me