In the circuit shown below, viewed from AB, the circuit

In the circuit shown below, viewed from AB, the circuit can be reduced to an equivalent circuit as—

1. 5V source in series with 10Ω resistor
2. 7V source in series with 2·4Ω resistor
3. 15V source in series with 2·4Ω resistor
4. 1V source in series with 10Ω resistor

The given circuit:

Equivalent circuit for R_th

From figure, R_th = 4|| 6 = 2·4Ω
V_th = 10 – 6 I
where,

l =	10 - 5	=	5	= 0.5A
	6 + 4		10

Now,
V_th = 10 – 6 × 0·5 = 10 – 3 = 7V