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## Homework Statement

The problem ask for Thevenin Equivalent for the circuit attached.

## Homework Equations

Vth = Vab

Rth = Req

Rth = Vth / Isc

Rth = 1 / It

## The Attempt at a Solution

Already calculated Vth = 166.67 V. I've no problem with that. Already confirmed by textbook answer.

However, my issue is with Rth,

As per book there 3 methods to calculate Rth

1st Method : Kill independent sources and Rth = Req as seen by terminals. (Provided all sources in the circuit are independent).

2nd Method : Make a wire (short circuit) between a & b going from a to b. Calculate current of this wire (Isc), Req = Vth / Isc

3rd Method : Kill independent source, Put test voltage source with value 1 V, Put test current (It) going from - to + , calculate current, Rth = 1 / It

For the attached circuit, 1st method cannot be used as there is dependent source in the circuit.

I used third method and got Rth = 10 ohm, which is the correct answer.

My issue with the 2nd method !

If i used the second method and make short circuit between a & b, 10 ohm will be removed as it is parallel with short circuit. Then i calculate Isc and it is zero ! i used different methods (kcl kvl, mesh) still zero!

which will make Rth = 166.67 / 0 = infinity! which wrong for sure. Answer should be Rth = 10 ohm

My questions are :

(1) Did i summarize the methods correctly?

(2) Why is Isc = 0 when I use the second method?

Thanks in advance.