Experiment 5 Thevenin’s Theorem

Aim:

Verification of Thevenin’s Theorem

Components and Equipment Required:
Multimeter, power supply, breadboard, 3 resistors, connecting wires

Theory:
Thevenin’s theorem states that a linear two-terminal circuit can be replaced by an equivalent circuit consisting of a voltage source V_Th in series with a resistor R_Th, where V_Th is the open-circuit voltage at the terminals and R_Th is the input or equivalent resistance at the terminals when the independent sources are turned off.

The basic steps for solving a circuit using Thevenin’s Theorem is as follows:

• Remove the load resistor R_L or component concerned.
• Find R_TH by shorting all voltage sources or by open circuiting all the current sources.
• Find V_TH by the usual circuit analysis methods.
• Find the current flowing through the load resistor R_L.

Formulas used:

Circuit Diagram:

(Figure 1)

for vth (Figure 2)

For rth (Figure 3)

Procedure:

1. Connect the circuit as shown in figure-1.
2. Set the particular voltage value and note down all the readings.
3. Connect the circuit as in figure-2 to obtain the Thevenin’s voltage. To find the Thevenin source voltage (V_TH) remove the load resistor from the original circuit and calculate the voltage across the open connection.
4. Connect the circuit as in figure-3 to obtain Thevenin’s resistance. To find the Thevenin resistance (R_TH) by removing all power sources in the original circuit (voltage sources shorted and current sources open) and calculating total resistance between open connection points.

Observation Table:

                                                            Original circuit                                                Thevenin’s circuit

RL (Ω)	VL (V)	IL (mA)	VL (V)	IL (mA)

Result:

Thus, the Thevenin’s Theorem is verified.

Precautions:

1. Keep the circuit neat and clean
2. Check if power supply and ammeter are working properly.
3. Avoid short circuit of output terminal