Find the Thevenin voltage and resistance for the network

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Find the Thevenin voltage and resistance for the network shown below across the terminal A.B—

1. 27 V, 3 Ω
2. 18 V, 3 Ω
3. 27 V, 1 Ω
4. 18 V, 8 Ω

Correct Option: A

Calculation for R_th
To calculate R_th when dependent source are taking into account for this, assume a imaginary source say 5 V is connected across terminal A and B and current produced by that current source is I then R_th is given by the relation.
R_th = 5/1
the equivalent circuit for calculating R_th is shown below:
5 = 2 V_x + I. 1 ....(i)
V_x = 1. I
5 = 2 I + I

I =	5	Ω
	3

so, R_th =	5	= 3 Ω
	5 / 3

Calculation for Vth:
Here the 3 A current source will drop across 1 Ω resistance

V_x = 3 × 1 = 3 V
or V_th = 2 V_x + V_x + 18
or V_th =3 V_x + 18 = 3 × 3 + 18 = 27 V