ESKİŞEHİR TECHNICAL UNIVERSITY
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
EEM 102 INTRODUCTION TO ELECTRICAL ENGINEERING
EXPERIMENT 4
THEVENIN’S THEOREM
EXPERIMENT 4
THEVENIN’S THEOREM
OBJECTIVE:
To observe the results of the Thevenin’s Theorem practically.
INTRODUCTION:
Thevenin’s Theorem
Thevenin’s theorem says that a linear two-terminal network can be replaced by an ideal
voltage source VTh , which is equal to the open-circuit voltage Voc between the terminals, in series
with a resistance RTh, which is the resistance seen between the terminals with all the independent
sources killed.
Maximum Power: When a load RL is connected between the terminals A and B, it should be equal
to RTh to obtain maximum power in the load RL. In this case;
IL =
V
V
V
V2
=
, VL = RL I L = , PL = VL I L =
RTH + RL 2 RL
4 RL
2
Potentiometers: Potentiometers are actually resistors with a center tap as seen in the figure. They
can be used as voltage dividers.
R1 = Resistance between a and c.
R2 = Resistance between b and c.
R = R1 + R2 = Resistance between a and b.
Vout =
V
R2
R
.
Rheostas: Rheostas are actually potentiometers with b and c terminals shorted. Thus, they can
be used as variable resistors. Using terminals a and c of a potentiometer with b open will also
result in a variable resistor. Similarly, you may use b and c with a open.
PROCEDURE:
A. 1. Take R1 = 560 Ω, R2 = 1000 Ω, and R3 = 330 Ω. Measure the actual resistor values and
write them in Table 1.
2. Set up the circuit below.
Figure 1.
3. Measure the open circuit voltage Voc (VTh) between A and B. Write it in Table 2.
4. Connect a current meter between A and B to measure the short circuit current isc. Write it in
Table 2.
5. Disconnect the source E and short-circuit C and D. Then, measure the equivalent resistance
RTh seen by A and B. Write it in Table 2.
6. Find R*Th by dividing measured open circuit voltage Voc to short circuit current isc and write it
in Table 2.
7. Write the calculated Voc, isc and RTh values in Table 2.
8. Find R*Th by dividing calculated open circuit voltage Voc to short circuit current isc and write
it in Table 2.
B. 1. Take the R4 = 1 KΩ potentiometer and adjust its resistance to 100 Ω.
2. Connect the pot between A and B of Figure 1 and measure VAB and write it in Table 3.
3. Increment the resistance of the pot by 100 Ω and repeat step B.2 until you reach 1000 Ω.
4. Measure IR4 and calculate PR4 for each step.
5. Plot PR4 versus R4.
C. 1. Measure Voc between A and B in Figure 1.
2. Connect the R4 = 1 KΩ pot between A and B.
𝑉
𝑂𝐶
3. Adjust the pot until you read 𝑉𝐴𝐵 = 2 .
4. Take pot out carefully without changing its resistance and measure its resistance.
5. Fill out Table 4.
Name: …………………………..
No :…………………………......
Table No:……………………….
Group :…………………………..
EXPERIMENT 4
THEVENIN’S THEOREM
REPORT
A. TABLE -1 : Resistor values
Resistor
R1
R2
R3
Nominal
560
1000
330
Measured
TABLE -2 : Measured and calculated values of Voc, isc, and RTh.
Voc
isc
R*Th
RTh
Measured
Calculated
Compare the measured and calculated values of RTh and R*Th. Explain the differences between
them if any.
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B. TABLE -3 : Power obtained at the load.
R4 (ohms)
100
200
300
400
500
600
700
800
900
1000
VR4
IR4
PR4
Explain the behavior of the power that is obtained between A and B with its reasons.
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C. TABLE -4 :
Voc / 2
Voc
Measured R4
What can you say about the value of R4 ?
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Date:
Table No:
Name:
No:
Pre-Lab
Grades
Report
Performance
Total
0
