ANADOLU UNIVERSITY
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
EEM 102 INTRODUCTION TO ELECTRICAL ENGINEERING
EXPERIMENT 4
THEVENIN’S THEOREM
Prepared by Prof. Dr. Atila BARKANA
EXPERIMENT 4
THEVENIN’S THEOREM
OBJECTIVE:
To observe the results of the Thevenin’s Theorem practically.
PRELIMINARY WORK:
Do parts A and B of the PROCEDURE at home using the nominal values of the elements. Your
solutions and results should be hand written neatly on size A4 paper. Make sure you draw the
graph in part B of the PROCEDURE.
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, to obtained
maximum power in the load RL, it should be equal to RTh.
In this case
IL
V
RTH
RL
V
,
2 RL
VL = RL.IL =
V
,
2
PL = VL.IL
V2
4 RL
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 = 470 Ω, and R3 = 220 Ω. Measure the actual resistor values and
record them in Table 1.
2. Set up the circuit below.
Figure 1
3. Measure the open circuit voltage Voc 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. Write it in Table 2.
6. Calculate isc using the measured values of the resistors and write it in Table 2.
7. Calculate RTh using the measured values of the resistors 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 Figure1 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. Calculate IR4 and 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.
3. Adjust the pot until you read VAB =
VOC
.
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
RTh
R’Th =
Measured
Calculated
Compare the measured and calculated values of RTh and explain the difference.
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Compare the measured and calculated values of R’Th and explain the difference.
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Compare the measured and calculated values of RTh and R’Th and explain the difference.
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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
What can you say about the behavior of the power that can be obtained between A and B.
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C. TABLE -4 :
Voc
Voc / 2
Measured R4
What can you say about this value of R4 ?
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Date:
Table No:
Name:
No:
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