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Page 2
Superposition
It states that, in any linear circuit containing multiple independent sources, the total current
through or voltage across an element can be determined by algebraically adding the voltage or
current due to each independent source acting alone with all other independent source set to
zero.
Source Transformation
It states that as independent voltage source
S
V in series with a resistance R is equivalent to
independent current source ?
Ss
I V / R in parallel with a resistance R.
Or
An independent current source
S
I in parallel with a resistance R is equivalent to a dependent
source
SS
V I R ? in series with a resistance R.
Thevenin’s Theorem
It states that any network composed of ideal voltage and current source, and of linear resistor,
may be represented by an equivalent circuit consisting of an ideal voltage source
TH
V in series
with an equivalent resistance
TH
R .
Methods to calculate thevein equivalent
The therein voltage ? ?
TH
V is equal to open circuit voltage across load terminals.
Therein resistance is input or equivalent resistance at open circuit terminals (load terminals) when
all independent source are set to zero (voltage sources replaced by short circuit & current source
by OC)
Case – 1 : Circuit with independent sources only
Page 3
Superposition
It states that, in any linear circuit containing multiple independent sources, the total current
through or voltage across an element can be determined by algebraically adding the voltage or
current due to each independent source acting alone with all other independent source set to
zero.
Source Transformation
It states that as independent voltage source
S
V in series with a resistance R is equivalent to
independent current source ?
Ss
I V / R in parallel with a resistance R.
Or
An independent current source
S
I in parallel with a resistance R is equivalent to a dependent
source
SS
V I R ? in series with a resistance R.
Thevenin’s Theorem
It states that any network composed of ideal voltage and current source, and of linear resistor,
may be represented by an equivalent circuit consisting of an ideal voltage source
TH
V in series
with an equivalent resistance
TH
R .
Methods to calculate thevein equivalent
The therein voltage ? ?
TH
V is equal to open circuit voltage across load terminals.
Therein resistance is input or equivalent resistance at open circuit terminals (load terminals) when
all independent source are set to zero (voltage sources replaced by short circuit & current source
by OC)
Case – 1 : Circuit with independent sources only
To calculate
TH
V , open circuit of RL
Using sources transformation
? ? ?
?
TH
2
V 24 12V
22
To calculate Rth
Short I & V sources & open 6mA source
? ?
? ? ? ? ?
th
R 1 2 1 1 2k
Page 4
Superposition
It states that, in any linear circuit containing multiple independent sources, the total current
through or voltage across an element can be determined by algebraically adding the voltage or
current due to each independent source acting alone with all other independent source set to
zero.
Source Transformation
It states that as independent voltage source
S
V in series with a resistance R is equivalent to
independent current source ?
Ss
I V / R in parallel with a resistance R.
Or
An independent current source
S
I in parallel with a resistance R is equivalent to a dependent
source
SS
V I R ? in series with a resistance R.
Thevenin’s Theorem
It states that any network composed of ideal voltage and current source, and of linear resistor,
may be represented by an equivalent circuit consisting of an ideal voltage source
TH
V in series
with an equivalent resistance
TH
R .
Methods to calculate thevein equivalent
The therein voltage ? ?
TH
V is equal to open circuit voltage across load terminals.
Therein resistance is input or equivalent resistance at open circuit terminals (load terminals) when
all independent source are set to zero (voltage sources replaced by short circuit & current source
by OC)
Case – 1 : Circuit with independent sources only
To calculate
TH
V , open circuit of RL
Using sources transformation
? ? ?
?
TH
2
V 24 12V
22
To calculate Rth
Short I & V sources & open 6mA source
? ?
? ? ? ? ?
th
R 1 2 1 1 2k
Case – 1 : Circuit with both dependent & independent sources
Methodology 1:
?
Th
V can be found in same way.
? For
TH
R set all independent sources to zero.
? Remove load & put a test source
test
V across its terminals, let current through test source is
test
I .
? ?
test
TH
test
Thevenin resistance ,
V
R
I
? This method is must if independent sources are absent.
Methodology 2:
?
TH
V is calculated in same way.
? For
TH
R short circuit load terminals & leave independent sources as it is
? Obtain
SC
I through load terminals.
?
TH OC SC
R V I ?
Norton’s Theorem
Any network composed ideal voltage & current sources, and of linear resistors, may be
represented by an equivalent circuit consisting of an ideal current source
N
I in parallel with an
equivalent resistance
N
R .
? ?
N TH
RR
? To calculate
N
I we short circuit load terminals & calculate short circuit current.
? Therein equivalent & Norton equivalent are dual of each other.
Page 5
Superposition
It states that, in any linear circuit containing multiple independent sources, the total current
through or voltage across an element can be determined by algebraically adding the voltage or
current due to each independent source acting alone with all other independent source set to
zero.
Source Transformation
It states that as independent voltage source
S
V in series with a resistance R is equivalent to
independent current source ?
Ss
I V / R in parallel with a resistance R.
Or
An independent current source
S
I in parallel with a resistance R is equivalent to a dependent
source
SS
V I R ? in series with a resistance R.
Thevenin’s Theorem
It states that any network composed of ideal voltage and current source, and of linear resistor,
may be represented by an equivalent circuit consisting of an ideal voltage source
TH
V in series
with an equivalent resistance
TH
R .
Methods to calculate thevein equivalent
The therein voltage ? ?
TH
V is equal to open circuit voltage across load terminals.
Therein resistance is input or equivalent resistance at open circuit terminals (load terminals) when
all independent source are set to zero (voltage sources replaced by short circuit & current source
by OC)
Case – 1 : Circuit with independent sources only
To calculate
TH
V , open circuit of RL
Using sources transformation
? ? ?
?
TH
2
V 24 12V
22
To calculate Rth
Short I & V sources & open 6mA source
? ?
? ? ? ? ?
th
R 1 2 1 1 2k
Case – 1 : Circuit with both dependent & independent sources
Methodology 1:
?
Th
V can be found in same way.
? For
TH
R set all independent sources to zero.
? Remove load & put a test source
test
V across its terminals, let current through test source is
test
I .
? ?
test
TH
test
Thevenin resistance ,
V
R
I
? This method is must if independent sources are absent.
Methodology 2:
?
TH
V is calculated in same way.
? For
TH
R short circuit load terminals & leave independent sources as it is
? Obtain
SC
I through load terminals.
?
TH OC SC
R V I ?
Norton’s Theorem
Any network composed ideal voltage & current sources, and of linear resistors, may be
represented by an equivalent circuit consisting of an ideal current source
N
I in parallel with an
equivalent resistance
N
R .
? ?
N TH
RR
? To calculate
N
I we short circuit load terminals & calculate short circuit current.
? Therein equivalent & Norton equivalent are dual of each other.
Maximum Power Transfer Theorem:
A load resistance
L
R will receive maximum power from a circuit when load resistance is equal to
Thevenin’s/ Norton’s resistance seen at load terminals.
?
L Th
RR
In case of AC circuit, this condition translates to
?
L
*
th
ZZ
? But if load is resistive in AC circuit then
?
L Th
RZ
?
For maximum power transfer
? ?
? ? ?
2
2
LL Th Th
R R X X
?
For maximum power transfer
L Th
X X 0 ??
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