Title: Thevenin’s theory.
Aim: Using thevenin’s theory to find current of the load.
Theory:
Thevenin theory states that a linear two-terminal circuit can be replaced by an equivalent circuit
consisting of a voltage source VTh (Thevenin voltage) in series with a resistor RTh (Thevenin
resistance), where VTh is the open-circuit voltage at the terminals and RTh is the input or
equivalent resistance at the terminals when the independent sources are turned off. To find the
Thevenin resistance switch off all independent sources by shorting all voltage sources as shown
(A).
(A) R1 (A) R1
Remove the resistive load (RL) for which current is to be found (B).
(B)
The equivalent Thevenin resistance is found by combining all the resistors in the circuit
(C)
With the help voltage divider rule use the original circuit to find the voltage across the load (A).
After finding the Thevenin resistance and the Thevenin voltage the circuit will be likewise.
, 𝑉Th
Use the following formula to find the current across the load (RL) IL = 𝑅Th + 𝑅𝐿
Method:
1. Choose three resistors for R1, R2 and RL. Measure their resistance values by using a
multimeter.
2. Using a voltage power supply and the three resistors set up the circuit as shown below.
R1
3. Remove the resistor containing the load (RL) as shown below.
4. Using a digital multimeter measure the voltage across terminal “a” and “b” with no load
connect. This is the voltage Thevenin equivalent.
5. Repeat step four 2 times and record in the table.
6. Remove the voltage source and connect an ohmmeter across points “a” and “b”. This is
equivalent to the Thevenin Resistance.
7. Calculate the current through the load considering all measurements (step’s 4 and 5)
using the following formula:
𝑉Th
IR =
𝑅Th + 𝑅𝐿
Aim: Using thevenin’s theory to find current of the load.
Theory:
Thevenin theory states that a linear two-terminal circuit can be replaced by an equivalent circuit
consisting of a voltage source VTh (Thevenin voltage) in series with a resistor RTh (Thevenin
resistance), where VTh is the open-circuit voltage at the terminals and RTh is the input or
equivalent resistance at the terminals when the independent sources are turned off. To find the
Thevenin resistance switch off all independent sources by shorting all voltage sources as shown
(A).
(A) R1 (A) R1
Remove the resistive load (RL) for which current is to be found (B).
(B)
The equivalent Thevenin resistance is found by combining all the resistors in the circuit
(C)
With the help voltage divider rule use the original circuit to find the voltage across the load (A).
After finding the Thevenin resistance and the Thevenin voltage the circuit will be likewise.
, 𝑉Th
Use the following formula to find the current across the load (RL) IL = 𝑅Th + 𝑅𝐿
Method:
1. Choose three resistors for R1, R2 and RL. Measure their resistance values by using a
multimeter.
2. Using a voltage power supply and the three resistors set up the circuit as shown below.
R1
3. Remove the resistor containing the load (RL) as shown below.
4. Using a digital multimeter measure the voltage across terminal “a” and “b” with no load
connect. This is the voltage Thevenin equivalent.
5. Repeat step four 2 times and record in the table.
6. Remove the voltage source and connect an ohmmeter across points “a” and “b”. This is
equivalent to the Thevenin Resistance.
7. Calculate the current through the load considering all measurements (step’s 4 and 5)
using the following formula:
𝑉Th
IR =
𝑅Th + 𝑅𝐿
