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  #1  
Old 12-12-2010, 10:21 AM
RedDead RedDead is offline
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Default Thevenin Equivalent with a dependent source

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
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  #2  
Old 12-12-2010, 10:51 AM
Jony130 Jony130 is offline
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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)
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  #3  
Old 12-12-2010, 11:11 AM
RedDead RedDead is offline
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Quote:
Originally Posted by Jony130 View Post
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?
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Old 12-12-2010, 01:10 PM
Jony130 Jony130 is offline
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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.
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  #5  
Old 12-12-2010, 01:31 PM
RedDead RedDead is offline
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thank you, you are brilliant

Last edited by RedDead; 12-12-2010 at 01:38 PM.
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  #6  
Old 12-12-2010, 01:43 PM
RedDead RedDead is offline
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Quote:
Originally Posted by Jony130 View Post
Well first you need to find Vth voltages



but where is the 4 ohm resistor which is parallel to the 8 volt source?
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  #7  
Old 12-12-2010, 01:50 PM
Jony130 Jony130 is offline
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Well I remove this resistor becaues it is connect parallel to the voltage source.
So this resistor has no effect on Va voltages.
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  #8  
Old 12-12-2010, 02:17 PM
RedDead RedDead is offline
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Quote:
Originally Posted by Jony130 View Post
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
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