The Thévénin Equivalent of a circuit consists of a Thévénin voltage source in series with a Thévénin resistor
and is valid for any load. In AC circuits a Thévénin equivalent circuit is valid for a single frequency.
Original Circuit Prior to the Thévénin Equivalent
Thévénin Equivalent
The Thévénin voltage is the open circuit voltage at the output. calculation is straightforward node or loop circuit
analysis. Using loop analysis:
V_{oc}: [8 * I1] + [(8+2+6) * I2]  [6 * I3] = 1 A
I2 = ½A ==> Voc = ½A * 6
Ω= 3 V = V_{th}
Calculate the Thévénin resistance from the open circuit voltage and the short circuit current (set R_{L}
= 0 and solve for I3) using Ohm's Law.
R_{th} = V_{oc} / I_{sc} = 3 V / [(4/9) A] = 27 / 4 Ω = R_{th}
