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CHITTAGONG UNIVERSITY OF ENGINEERING AND TECHNOLOGY
DEPARTMENT OF MECHANICAL ENGINEERING,
CHATTOGRAM-4349, BANGLADESH.
COURSE NO.: EEE 132
Experiment No. 4
Verification of the Thevenin’s Theorem
Instructions:
Revise the lecture notes on the topic Thevenin’s Theorem (Course code: EEE 131).
Read this laboratory manual carefully prior to start the laboratory class.
DO NOT copy others.
Submit your lab report before the roll call.
Objective:
(a) Experimental verification of the Thevenin’s Theorem
Required Instruments:
1) Variable DC Power Supply
2) Multi-meter/voltmeter
3) Ammeter
4) Resistors
5) Connecting Wires
6) Bread board
Thevenin’s Theorem: The Thevenin’s theorem states that any two terminal linear bilateral
network containing sources and passive elements can be replaced by an equivalent circuit
consist of a voltage source VTh in series a resistor RTh where –
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Figure – 1: Equivalent Circuit of the Thevenin’s Theorem
VTh = The open circuit voltage (VOC) at the two terminals a and b.
RTh = The resistance looking into the terminals A and B of the network with all sources
removed.
There are several methods for determining Thevenin resistance RTh. An attractive method for
determining RTh is:
1. Determine the open circuit voltage
2. Determine the short circuit current ISC as shown in the figure
Figure – 2: Circuit diagram for measuring RTh
Circuit Diagram:
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Figure – 3: Original Circuit Diagram
Figure – 4: Circuit Diagram for finding Voc
Figure – 5: Circuit for finding Isc
Figure – 6: Thevenin equivalent circuit for figure - 3
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Steps to follow:
1. Connect the three resistors R1, R2 and R3 with a variable DC power supply as shown in
Figure – 03.
2. Measure VL and IL for different RL and record the data in Table.
3. Remove the load resistance RL and find the open circuit voltage between terminals A
& B. This voltage is Thevenin voltage i.e. VTh=VOC.
4. Place a short circuit between terminals A & B and find the short circuit current ISC.
Divide the open circuit voltage by the short circuit current to find the Thevenin
resistance RTh.
5. Construct the Thevenin’s equivalent circuit as shown in Figure – 6, setting the power
supply at VTh volts and the resistor at RTh ohms. Now measure the load current IL and
the load voltage VL for the values of RL determined in step 2. Compare these values
with previous values.
Experimental Data:
Table – 1: Data for Original Circuit
R1 = R2 = R3 = V=
No. of Obs. RL (ohms) VL (volts) IL (amps)
01.
02.
03.
04.
05.
VTh = RTh =
Table – 2: Data for Thevenin Circuit
No. of Obs. RL (ohms) VL (volts) IL (amps)
01.
02.
03.
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04.
05.
Reports:
1. Provide the results in tabular form.
2. Comment on the results and anomalies (if any).
Home Task:
Include the answers of the following questions in your lab report –
1. Define unilateral, bilateral & equivalent circuit.
2. Describe other methods for determining Thevenin resistance.
3. Mention the advantages of using Thevenin Theorem.
