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FAKULTI KEJURUTERAAN ELEKTRIK
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Nama Matapelajaran : MAKMAL KEJ. ELEKTRIK
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Kod Matapelajaran
: SEE 2742
No. Prosedur
:3
: Julai 2008
: 2005
: PK-UTM-FKE-(O)-10
SEE 2742
FAKULTI KEJURUTERAAN ELEKTRIK
UNIVERSITI TEKNOLOGI MALAYSIA
KAMPUS SKUDAI
JOHOR
ELECTROTECHNIC LABORATORY
THEVENIN AND NORTON THEOREMS
(Experiment 3)
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1
FAKULTI KEJURUTERAAN ELEKTRIK
UNIVERSITI TEKNOLOGI MALAYSIA
ELECTROTECHNIC LABORATORY
EXPERIMENT
: 3
TITLE
: THEVENIN AND NORTON THEOREMS
1.
PRELIMINARY EXCERCISES
[You are required to do this exercise before conducting the experiment. In order to
complete this exercise, you may need to refer to any textbook such as ‘Fundamentals of
Electric Circuits, 3th Alexander & Sadiku, McGraw Hill’]
2.
(a)
For the circuit in Fig. 10, calculate IL at RL = 0 Ω; 10 Ω: 20 Ω; 30 Ω; 50 Ω;
100 Ω and 200 Ω
(b)
What are the two component of a Thevenin and Norton equivalent circuit?
(c)
Define Thevenin equivalent voltage, VTH
(d)
Define Thevenin equivalent resistance, RTH
(e)
For the original circuit in Figure 1.0, determine the Thevenin and Norton
equivalent circuit as viewed from terminals A and B. hence, calculate IL at
RL = 0 Ω; 10 Ω: 20 Ω; 30 Ω; 50 Ω; 100 Ω and 200 Ω
(f)
State the maximum power transfer theorem. Show that for maximum power
transfer, RL = RTH.
Aims :
i.
To obtain Thevenin and Norton equivalent circuit from a complex circuit.
ii.
To perform comparison analysis between the complex circuit and the
Thevenin and Norton equivalent circuits.
iii.
To show that Thevenin and Norton theorems are the simplest method to
analyze simple and complex circuits.
iv.
To determine the value of load resistance for which maximum power is
transferred.
2
3.
Theory :
It often occurs in practice that a particular element in a circuit is variable (usually
called the load) while other elements are fixed. Each time the variable element is
changed, the entire circuit has to be analyzed all over again. To avoid this
problem, Thevenin and Norton Theorems provide a technique by which the
complex circuit is replaced by an equivalent circuit.
Thevenin’s theorem states that a linear two-terminal circuit (refer Figure (a)) can
be replaced by an equivalent circuit called Thevenin equivalent circuit consisting
of a voltage source VTH in series with an equivalent resistance RTH (refer Figure
(b)), where VTH is the open-circuit voltage at the terminals and RTH is the input or
the equivalent resistance at the terminals.
Norton’s theorem states that a linear two-terminal circuit (refer Figure (a)) can
be replaced by an equivalent circuit called Norton equivalent circuit consisting of
a current source IN in parallel with an equivalent resistance RN (refer Figure (c)),
where IN is the short-circuit current through the terminals and RN is the input or
the equivalent resistance at the terminals.
Rth
A
VS1
RL
B
R2
R1
IS
Vth
Figure (b): Thevenin Equivalent Circuit
A
R3
RL
VS2
A
B
IN
RL
RN
B
Figure(a) Complex Circuit
Figure (c): Norton Equivalent Circuit
Thevenin equivalent resistance and Norton equivalent resistance are equal; that is,
RTH = RN
Thevenin voltage ,
VTH = IN x RN
Norton current ,
IN =
VTH
RTH
3
Therefore the Norton equivalent circuit can be obtained from the Thevenin equivalent
circuit or vice-versa.
4.
Equipments:
No
1
Equipments
Resistor 12Ω , 10Ω, 150Ω, 20Ω, 100Ω
2
Decade resistor
3
Ampere meter
4
Volt meter
5
Multimeter
6
DC power supply
7
Connection wire
5.
Procedures :
Serial No.
Experiment A : Load current measurement in complex circuit.
i.
Circuit connection (refer to Figure 1.0).
10 Ω
12 Ω
18 V
150 Ω
A
A
IL
RL
100 Ω
B
Figure 1.0
ii.
Measure and record the ammeter readings for load resistance, RL = 0 Ω;
10 Ω: 20 Ω; 30 Ω; 50 Ω; 100 Ω and 200 Ω (Table 1.0)
4
Experiment B : Thevenin and Norton Theorem
i.
ii.
From Figure 1.0, open the terminals A and B.
a.
Measure the Thevenin equivalent resistance, RTH at terminals A and B.
b.
Measure the open circuit voltage at terminals A and B.
c.
Measure the short circuit current at terminals A and B.
Use the measured value of equivalent resistance, RTH and open circuit
voltage, VTH, connect the circuit as in Figure 2.0, measured and record
ammeter reading in Table 2.0.
RTH
A
A
VTH
RL
B
Figure 2.0
iii.
Use the measured value of equivalent resistance, RTH and short circuit
current, IN, connect the circuit as in Figure 3.0, Adjust the voltage supply
(E) to achieve the Norton current IN. measured and record ammeter reading
in Table 3.0.
10 Ω
A
A
IN
RN
E
RL
B
Figure 3.0
5
A