Thevenin’s theorem states that any linear circuit no matter how complex can be replaced by an equivalent circuit with a single voltage source in series with a resistance. The equivalent voltage, known as the Thevenin voltage, is denoted by Vth and the equivalent resistance, known as Thevenin resistance, as Rth. Suppose it is required to find the voltage and current across a certain load resistor in a given circuit. Then to find the Vth we remove the load resistor and calculate the voltage across the terminals. To find the Rth short the sources in the circuit and find the resistance across the load resistance. The equivalent circuit is made by replacing the actual circuit by its Thevenin equivalent across the load.