LAB 2 PART B: Network Theorems II
1. Thevenin Theorem
Introduction:
This lab focuses on the Thévenin theorem. Complex circuits are often replaced with their Thévenin
equivalent to simplify analysis. For example, in the analysis of large industrial power systems the Thévenin
equivalent is used in short circuit studies.
Objective:
By the end of this lab, the student should be able to verify Thévenin's equivalence theorem.
Preparation:
Read the material in the textbook that describes Thévenin's equivalence theorem.
Equipment Needed:
NI-ELVIS workstation. Individual resistors as required. Resistance substitution box.
Procedure:
1)
This part of the lab illustrates the use of Thévenin's theorem. Adjust the output of the DC
power supply to 10V (on the VPS window opened on the NI Instrument Launcher). Set up the circuit
as shown in Fig. 5.1. Measure the open circuit voltage and short circuit current between nodes A and
B with load resistor (RL) removed. Using these measurements, determine the Thévenin equivalent
circuit. Set up the newly determined Thévenin equivalent circuit and verify that this circuit has the
same open circuit voltage and short circuit current as the previous circuit. Save this circuit for Part 2.
Figure 5.1 - Determining the Thévenin equivalent circuit.
2). This part of the lab is to illustrate maximum power transfer. Use the Thévenin equivalent circuit
developed in part 1 as in figure 5.2. Measure the current through and voltage across RL if RL = 0-Ω.
Then repeat for RL = 20-Ω, 40-Ω, 60-Ω, 80-Ω, 100-Ω, 120-Ω, 140-Ω, 160-Ω, 170Ω, 175-Ω, 177-Ω,
179-Ω, 180-Ω, 200-Ω 220-Ω 240-Ω. Determine the power dissipated by the resistor for each value of
R. Plot power vs. resistance. At which value is the power maximum?
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Report:
Your lab report is due during next lab session.
NOTE: Every student MUST come with a Pre-lab report (showing tables and calculations)
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2. Norton’s Theorem
Aim
To verify Norton’s Theorem for a linear network.
Equipment needed:
NAME
1. Bread Board.
2. Resistors
3. Voltmeter
4. Ammeter
5. Ohm-meter
RANGE
QUANTITY
5.6-KΩ
1-KΩ
3
1
1
1
1
Theory:
Any linear bilateral network containing one or more current sources can be replaced by an
equivalent circuit consisting of an equivalent current source, in parallel with an equivalent
resistance. Value of current source is equal to the short circuit current through the output
terminals with the load resistance shorted.
The Norton’s equivalent resistance is equal to the effective resistance measured between the
output terminals with the load resistance removed, and with all the energy sources replaced
by their internal resistances. (RESISTORS TO BE USED ARE 5.6-KΩ )
Procedure:
1. Connect the circuit as per CIRCUIT-1. Note down the current through the load
resistance.
2. Calculate the value of short circuit current, Norton’s equivalent resistance and
the current through the load resistance using Norton’s theorem.
3. Find out RNORTON by shorting the voltage source and measuring the equivalent
resistance across open circuited RLoad (1KΩ) terminals using a multimeter. Compare
this value with the calculated value.
4. Remove the load resistor RLoad and connect the circuit as per CIRCUIT-2 and
Note down the reading of ammeter as INORTON
5. Connect the Norton’s equivalent circuit as shown in CIRCUIT-3 and Note
down the reading of ammeter.
6. If current through the load resistance using Norton’s theorem is equal to the
measured value of the current from circuit1, Norton’s Theorems is verified.
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Observations:
Theoretical:
Short circuit current IN =
Norton’s
Equivalent
Resistance RN = Current
through the load resistor IL =
Measured:
Short circuit current IN =
Norton’s
Equivalent
Resistance RN = Current
through the load resistor IL =
Results:
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