Ex. No: 1 VERIFICATION OF THEVININ’S THEOREMS
AIM:
The aim of this exercise is to examine the use of Thévenin’s Theorem to create
simpler versions of DC circuits as an aide to analysis.
APPARATUS REQUIRED:
S. No
Name of the Apparatus
Range
Type
Quantity
1
Voltmeters
(0-30)V
MC
1
2
Ammeters
(0-50)mA
MC
1
3
RPS
(0-30)V
1
4
Resistors
2KΩ,1Ω
2,2
5
Bread board
1
6
Connecting wires
As required
THEORY:
Any linear, bilateral network having a number of voltage, current sources and resistances can
be replaced by a simple equivalent circuit consisting of a single voltage source in series with a
resistance, where the value of the voltage source is equal to the open circuit voltage and the
resistance is the equivalent resistance measured between the open circuit terminals with all energy
sources replaced by their ideal internal resistances.
Steps for finding Thevenin's Equivalent Circuit
1. Obtain THEVENIN’S EQUIVALENT RESISTANCE, RTH:
To obtain Thevenin’s Equivalent Resistance RTH, short circuit all the voltage sources and
open circuit the current sources (if any). Remove the load resistor RL, By viewing into the network
from the load terminals AB, determine the value of RT H.
2. OBTAIN OPEN CIRCUIT VOLTAGE VOC:
To obtain the open circuit voltage (VTH or VOC) across terminals AB of the network,
using mesh analysis determines the current in loop. Determine voltage drop across the resistor
between terminals. This voltage is equal to the open circuit or Thevenin’s voltage.
3. THE THEVENIN’S EQUIVALENT CIRCUIT:
The Thevenin’s equivalent circuit is as shown in step- 4 is drawn with a voltage Source in
series with Thevenin’s resistance RT H. Now connect the load resistor RL, to the equivalent circuit
and find the current through that resistance.
4. THE THEVENIN’SCIRCUIT LOADCURRENT:
IL = VTH / (R TH + RL)
PRECAUTIONS:
1. Switch off the supply while giving connections
2. Check for zero readings of the meters.
PROCEDURE:
1. Connections are made as per the circuit diagram
2. Set a particular value of voltage using RPS and note down the corresponding
ammeter readings.
To find VTH
3. Remove the load resistance and measure the open circuit voltage using multimeter (VTH).
To find RTH
4. To find the Thevenin’s resistance, remove the RPS and short circuit it and find the RTH
using multimeter.
5. Give the connections for equivalent circuit and set VTH and RTH and note the
corresponding ammeter reading.
6. Verify Thevenins theorem.
CIRCUIT:
Observation
Supply Voltage: 20 V
Electrical
Quantity
Vth or open
circuit voltage
(Vth)
Thevenin’s
equivalent
resistance
Local Current
Actual Network
Equivalent
Network
Theoretical
Practical
simulation
Percent error
(Theoretical Vs
Practical)
THEORETICALCALCULATIONS:
Analysis:
1. When RL=2KOHM, Do the circuit analysis and make a comment on which is faster,
analyzing each load with the original circuit or analyzing each load with the Thévenin
equivalent.
2. Do the load voltages for the original and Thévenin circuits match for both loads? Is
it logical that this could be extended to any arbitrary load resistance value?
RESULT:
Thus, the thevenin’s theorem was verified with the given network and the load current was
determined.
Ex. No 2: VERIFICATION OF NORTON’S THEOREM
AIM:
To verify Norton’s theorem for the given network and to find the load current.
APPARATUS REQUIRED:
S. No
Name of the Apparatus
Range
Type
Quantity
1
Voltmeters
(0-30)V
MC
1
2
Ammeters
(0-50)mA
MC
1
3
RPS
(0-30)V
1
4
Resistors
2KΩ,1KΩ
2,2
5
Bread board
1
6
Connecting wires
As required
THEORY:
Statement:
A complex network consist of a linear, bilateral, active or passive elements with two
accessible terminals can be reduced to a single current source (IN) connected in parallel with
equivalent Thevenin’s resistance(RTH).
Steps for finding Norton’s Equivalent Circuit
1. NORTONS’S EQUIVALENT RESISTANCE, RN:
To obtain Norton’s Equivalent Resistance RN, short circuit all voltage sources and open
circuit the current sources (if any). Remove the load resistor RL, by viewing into the network
from the load terminals AB, determine the value of RN.
2. THE SHORT CIRCUIT CURRENT ISC:
To obtain the short circuit current (IN or ISC) across to terminals AB of the network, using
mesh current analysis determines the current in loops as ISC. This current is equal to Norton’s
current or short circuit current.
3. THE NORTON’S EQUIVALENTCIRCUIT:
The Norton’s equivalent circuit is drawn with a current source is parallel with Thevenin’s
resistance RTH. Now connect that load resistor RL to the equivalent circuit and find the
current through that load resistance (using current divided rule).
4. THE NORTON’S CIRCUIT LOAD CURRENT:
IL=ISC[(RTH/(RTH+RL)]
PRECAUTIONS:
1. Switch off the supply while giving connections
2. Check for zero readings of the meters.
Procedure:
1. Connections are given as per circuit diagram.
2. Set a particular value in RPS and note down the ammeter readings in the original
circuit.
To Find IN:
3. Remove the load resistance and short circuit the terminals.
4. For the same RPS voltage note down the ammeter readings.
To Find RN:
5. Remove RPS and short circuit the terminal and remove the load and note down
the resistance across the two terminals.
Equivalent Circuit:
6. Set IN and RN and note down the ammeter readings.
7. Verify Norton’s theorem.
CIRCUIT
NORTON’S EQUIVALENTCIRCUIT:
TABULAR COLUMN:
Supply Voltage: 20V
Electrical
Quantity
Short Circuit
current
Norton’s
equivalent
resistance
Local Current
Actual Network
Equivalent
Network
Theoretical
Practical
simulation
Percent error
(Theoretical Vs
Practical)
THEORETICAL CALCULATIONS:
Analysis:
1. When RL=3KOHM, Do the circuit analysis and make a comment on which is faster,
analyzing each load with the original circuit or analyzing each load with the Norton’s
equivalent.
RESULT:
Thus, the Norton’s theorem was verified with the given network and the load current was
determined.