ACTIVE AND PASSIVE ELEMENTS IN A CIRCUIT
SEC B
GROUP II
ACTIVE AND PASSIVE
ELEMENTS
IN A CIRCUIT
3/21/2013
F.E CIS SEC.B
GROUP II
CS-114 NABIA WASEEM
CS-079 RABIYA WASEEM
CS-081 UMMUL AALA
THE REPORTS DESCRIBES THE TYPES OF ACTIVE AND PASSIVE ELEMENTS THAT
COMPLETES THE CIRCUIT AND THUS ARE A PART OF CIRCUIT ANALYSIS.
ACTIVE AND PASSIVE ELEMENTS IN A CIRCUIT
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GROUP II
TABLE OF CONTENTS
S.NO CONTENTS
DESCRIPTION
1 INTRODUCTION
2 WHAT ARE ACTIVE ELEMENTS
*INDEPENDENT SOURCES
*DEPENDENT SOURCES
EXAMPLES
*GENERATORS
*BATTERIES
*OP-AMPS
*TRANSISTORS
*VACUUM TUBES
3 WHAT ARE PASSIVE ELEMENTS
*RESISTORS
*CAPACITORS
*INDUCTORS
4 ANSWERS TO POSSIBLE QUESTIONS
5 SOURCE USED(BIBLIOGRAPHY)
PAGE
NO:
ACTIVE AND PASSIVE ELEMENTS IN A CIRCUIT
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INTRODUCTION
IN THE NAME OF ALLAH THE MOST BENEFICENT AND THE MOST MERCIFUL
First of all, we, group II members, would like to thank MAM ARJUMAND for providing us with the
opportunity to work over the topic of circuit analysis and research on the topic of ACTIVE AND
PASSIVE elements that would enhance our abilities to better understand the topic, thereby
solving circuits more easily.
Circuit analysis is a wider area or electrical engineering that deals
with circuit and the development of the circuits that actually runs at
the back of the system providing energy to many of the appliances and
other electrical elements attached. How the system works? How the
current we provide serves the elements attached? How much current
is sufficient for the circuit to function properly? Several questions like
these are answered in the study of circuit analysis.
Circuit analysis is the process by which voltage or current is measured across the element. All the
circuit elements can be categorized into two types: active and passive elements that play a salient role
in the circuit formation .these elements contribute to the circuit by fulfilling the requirements needed
behind the objective of its development. They are connected by wires to form a closed path thus
allowing current to flow.
To establish a flow of charge in a closed path, it is necessary to exert a kind of force on the electrons
that carries the charge known as the electromotive force. It can be a current or a voltage source.
This report describes a detailed study of what the active and passive elements are and how they
function and its applications. It contains all the indispensable details about how these elements are
majorly controlling the working of the circuit. With the help of circuit representations, the
performance and behavior of any electrical/electronic device can be studied in simple, accurate and
efficacious manner.
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ACTIVE ELEMENTS:
What are active elements?
An active element is a component or a device in a circuit that is capable of generating or producing
energy. In reality, energy is stored in the active elements in non-electrical form that is then converted
into electrical form. Active elements can be categorized into current and voltage sources as both
provide a drive to the circuit and manage the flow in it. Voltage sources are those sources due to
which the voltage at the terminal is equal to the voltage present internally. On the other hand,current
sources keep the terminal current same to that of the internal current. Thus voltage sources have series
impedances which are relatively same, while current sources would have shunt admittances almost
equals to zero.
In an ideal voltage source the current from the source varies depending upon the loadconnected.
Likewise in an ideal current source, the voltage across the source varies depending on the circuit
parameters. However, it is not possible practically to construct an ideal source.
Sources can be classified into two types: mainly independent sources and the dependent sources. In
independent sources, the generated voltage or current does not rely on any other circuit voltage or
current and the value is constant being unaffected. Whereas, dependent sources have the voltage that
depends on any other circuit current or voltage.
VCCS
VCVS
DEPENDENT SOURCES
CCCS
CCVS
ACTIVE ELEMENTS
INDEPENDENT
SOURCES
VOLTAGE OR
CURRENT
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INDEPENDENT SOURCES:
Independent sources are those that generate electrical energy. The output voltage of an
independent voltage or current source does not depend on any circuit element i.e. whatever
load or passive element is attached, its value of energy dissipation wills not alter.an ideal
voltage source has zero internal resistance and can never be short circuited.
Internal ideal current source has infinite internal resistance due to which maximum voltage
drop is there and all of the current flows out into the circuit. It can never be open circuited.
V-I
CHARACTERISTIC S
OF PRACTICAL
VOLTAGE SOURCE
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V-I
CHARACTERISTICS
OF PRACTICAL
CURRENT SOURCE
THE ABOVE TWO MENTIONED GRAPHS SHOWS HOW A PRACTICAL INDEPENDENT CURRENT AND
VOLTAGE SOURCE DIFFERS FROM THE IDEAL ONE.
DEPENDENT SOURCES:
Dependent sources, also referred to as controlled sources, do supple energy to
the circuit but they rely on any other factor, either current or voltage, of source
for their functionality.
There are four further categories of how these dependent sources rely on other
independent source of the circuit or even any varying quantity such as current or
voltage across a branch. These are usually representated b y a diamond shaped
source that shows that it is dependent.
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These descriptions are described as:

VOLTAGE CONTROLLED VOLTAGE SOURCE
 VOLTAGE CONTROLLED CURRENT SOURCE
 CURRENT CONTROLLED CURRENT SOURCE
 CURRENT CONTROLLED VOLTAGE SOURCE
VOLTAGE CONTROLLED VOLTAGE SOURCE (VCVS)
A voltage controlled voltage source has its output a factor times to the voltage at
any other point on the circuit.
Vs=αVx
Where α is a constant and Vx is the voltage across any given element.
VOLTAGE
CONTROLLED
CURRENT SOURCE (VCCS)
A voltage controlled current source has its output a factor times to the voltage at
any other point on the circuit. The output is current
Is=βvx
Where β is a constant and Vx is the voltage across any given element.
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CURRENT CONTROLLED CURRENT SOURCE (CCCS)
A current controlled current source gives an output that depends upon the
current
flowing through any part of the circuit. The output current is
Is=γIx
Where γ is a constant and Ix is the current across any given element.
CURRENT CONTROLLED VOLTAGE SOURCE:
A current controlled voltage source gives an output that depends upon the
current across any part of the circuit. The output voltage is
Vs=μIx
Where μ is a constant and Ix is the current flowing in the circuit taken into
consideration.
There are a number of active
elements that are both independent and dependent and so they contribute to the
contribute to the circuit by providing a flow into it.
ACTIVE AND PASSIVE ELEMENTS IN A CIRCUIT
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Some of them are mentioned below:
 Power supply
o A.c
o D.c
o Batteries
 Generators
 Transformers
 Transistors
 Operational amplifier
And many more.
This report gives a brief description of how these elements function thus
completing the circuit.
POWER SUPPLY:
A power supply is a device that supplies electric power to an electric
load. It controls the output voltage or current to a specific value; the
controlled value is held nearly constant despite variations in either load
current or voltage supplied by power supply’s energy source.
Common examples of this include
 Power supplies that convert ac line voltage to dc voltage.
 Energy storage devices such as batteries and fuel cells.
 Electromechanical systems such as generators and alternators.
 Solar power.
AC POWER SUPPLY
An ac power supply typically takes the voltage from the main supply and
makes it to the desired voltage. It is actually the sinusoidal wave form
that comes as an input to the circuit.
DC POWER SUPPLY:
It a straight line wave form that is constant and is rectified form of the
A.c supply. Batteries give D.c supply. Mobile phones operate on dc
supply.
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BATTERY:
A battery is a device that converts stored chemical energy to electrical
energy. USES:
Energy sources in many household
Industrial applications.
There are two types of batteries: primary batteries (disposable batteries),
which are designed to be used once and discarded, and secondary
batteries (rechargeable batteries), which are designed to be recharged and
used multiple times.
Batteries come in many sizes, from miniature cells used in hearing aids
and wristwatches to room-size battery banks that serve as backup power
supplies in telephone exchanges and computer data centers.
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GENERATORS:
Electric generator works over the principle of converting mechanical energy,
provided by the external system, into electrical energy by the principle of
magnetic induction. They provide power that runs machines in factories,
provides lighting, and operates homeappliances.
The size of large generators is usually measured in kilowatts. One kilowatt
equals 1,000 watts.
There are two main types of generators.
Direct-current (DC) generators produce electric current that always flows in the
same direction.
Alternating-current (AC) generators, or alternators, produce electric current that
reverses direction many times every second.
Both kinds of generators work on the same scientific principles. But they differ
in the ways they are built and used.
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TRANSFORMERS:
Transformers works over the principle of magnetic induction.there are two types
of winding namely primary and secondary. When a current is supplied to the
primary winding a magnetic flux is generated in the coil and by the law of
magnetic induction and continuous change in magnetic flux, a voltage is
induced at the secondary coil which is used as the output.
The number of turns of the coil usually contributes by increasing or decreasing
the output voltage. This is known as:
 Step up transformer: where voltage is increased at the output terminal.
 Step down transformer: that reduces the voltage at the output terminal.
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TRANSISTORS:
According to a website following description of transistor and its working is
shown.
http://www.cedengineering.com/upload/Transistors.pdf
Transistors
are
semiconductors
found
everywhere in electronic circuits. They are used
as amplifiers and switching devices. As
amplifiers, they are used in high and low
frequency stages, oscillators, modulators,
detectors and in any circuit needing to perform a
function. In digital circuits they are used as
switches.
Being forward or reverse biased, a transistor
allows current to pass through or even opposes it
depending upon its placement. Moreover, it
depends upon the base current flowing.
Some types of transistors are:




Bipolar junction transistor
Field- effect transistor
Diffusion transistor
Unijunction transistor, etc
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OPERATIONAL AMPLIFIER (op-amp):
An operational amplifier is a device used to compare between two voltages
being input into it and amplify it.
It is used as
 A comparator
It compares the two voltages that can be monitored in terms of
temperature change or light dependency as well. It involves the usage of
negative feedback where one output is used as an input next time.
 Inverting amplifier
It uses negative feedback but not all of the
output voltage is fed back into the inverting
input (-)
 Non inverting amplifier
Here the input voltage is applied to the noninverting input; part of the output voltage is
fed back to the inverting input.
Thus, by op-amp usage the gain is increased to a higher value but it is
made sure that the overall gain is almost the same due to which distortion
is less and the signal remain constant for large frequencies as well.
Gơ=output voltage/input voltage
An ideal op-amp has the following characteristics:
1. Infinite open loop gain voltage(no feedback used)
2. Infinite input resistance(no current drawn from supply)
3. Zero output resistance(no internal resistance no voltage drop)
4. Infinite bandwidth(same over large frequencies)
5. Infinite slew rate( time delay between input and output)
6. Zero noise contribution
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PASSIVE ELEMENTS
A passive component only absorbs energy or absorbs energy then later releases
it.
Main three types of passive components are:
1. Resistor
2. Capacitor
3. Inductor
 RESISTANCE
Definition:
“The hindrance or opposition offered by the atoms of a conductor in the flow of
electric current is called Resistance.”
Or
“It is a ratio of the potential difference to the current.”
Symbol:
Resistance is designated by the symbol R.
Unit:
The unit of measurement for resistance is ohms 𝜴.
Factors on which resistance depends:
The amount of resistance depends upon
1. Length
2. Cross-section
3. Temperature
4. Nature of the substances
OHM’S LAW DEFINES RESISTANCE:
In 19th century, German mathematician, George Simon Ohm gave the following
law: "Voltage across the conductor is directly proportional to the electric
current passes through a conductor."
VαI
V=IR
Relationship between current and voltage can be represented as,
ACTIVE AND PASSIVE ELEMENTS IN A CIRCUIT
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Figure 1 v-I relationship of an ideal resistor
OHM’S LAW TRIANGLE
There is an easy way to remember which formula to use.
COMBINATION OF RESISTANCES:
1. Serial Combination:
 It is formed when any numbers of resistors are connected in a circuit endto-end so that there is only one path for current to flow
 The total or equivalent resistance is always larger than the individual
resistance
 Current is the same anywhere it is measured in a series circuit
Total or equivalent resistance (Req) can be calculated as,
Req = R1 + R2 + R3 +…………………
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2. Parallel Combination:
 It is formed when two or more resistances are placed side-by-side so that
current can flow through more than one path.
 The total or equivalent resistance is always smaller than any individual
resistance
 Voltage is the same anywhere it is measured in a parallel circuit
Total or equivalent resistance (Req) can be calculated as,
𝟏
𝐑𝐞𝐪
=
𝟏
𝐑𝟏
+
𝟏
𝐑𝟐
+
𝟏
𝐑𝟑
…………….
Circuit Symbol:
Two ways are:
Units of Measurement
Special prefixes that are commonly used when dealing with values of
resistance:
Prefix
Symbol
Decimal
1 kilo ohm
1 KΩ
1000 Ω
1 mega ohm
1 MΩ
1,000,000 Ω
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COLOR CODING:
SOME OF THE DIFFERENT TYPES OF RESISTORS USED ARE:
 Axial
 Surface mount
GROUP II
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 CAPACITOR
Capacitor is made of two metal plates with separated by insulating material.
When a voltage is applied to the plates, electrons are forced onto one plate. The
plate with an excess of electrons is negatively charged. The plate with a
deficiency of electrons is positively charged.
Symbol: Capacitor is designated by the symbol
C. Unit: The unit of measurement for
capacitor is Farad (F).
Factors on which capacitance depend:
The amount of capacitor depends upon
1. Area of the plates
2. Distance between the plates
3. Material of the dielectric
Simple Capacitive Circuit
In the following circuit, initially the switch is open and no voltage is applied to
the
Capacitor and when the switch is closed, potential across the capacitor will rise
rapidly at first, then more slowly as the maximum value is approached.
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Combination of Capacitors:
1. Serial Combination:
 It is formed when any numbers of capacitors are connected in a circuit
end-to-end so that there is only one path for current to flow
 The total or equivalent capacitor is always smaller than the individual
capacitor
 Current is the same anywhere it is measured in a series circuit
Total or equivalent resistance (Ceq) can be calculated as,
𝟏
𝐂𝐞𝐪
=
𝟏
𝐂𝟏
+
𝟏
𝐂𝟐
+
𝟏
𝐂𝟑
…………….
2. Parallel Combination:
 It is formed when two or more capacitors are placed side-by-side so that
current can flow through more than one path
 The total or equivalent capacitor is always larger than any individual
capacitor
 Voltage is the same anywhere it is measured in a parallel circuit
Total or equivalent resistance (Ceq) can be calculated as,
Ceq = C1 + C2 + C3 +…………………
Circuit Symbol:
Two ways are:
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 INDUCTOR
Definition:
Inductance is the property of an electric circuit that opposes any change in
electric current.
Inductance opposes change in current flow.
Symbol:
Inductance is designated by the letter “L”.
Unit:
The unit of measurement for inductance is the Henry (H).
Expression:
The relationship between the time varying voltage across an inductor L and time
varying current passing through it can be expressed as,
V (t) = L
𝒅 𝒊(𝒕)
𝒅𝒕
Factors on which inductance depend:
The amount of inductance depends upon
1. Number of turns in the coil
2. Spacing between the turns
3. Coil diameter
4. Core material
5. Type of winding
Examples:
Examples are:
1. Transformers
2. Chokes
3. Motors
Simple Inductive Circuit
If an inductor is used, the current does not
change as quickly. In the following circuit,
initially the switch is open and there is no current
flow and when the switch is closed, current will
rise rapidly at first, then more slowly as the maximum value is approached.
ACTIVE AND PASSIVE ELEMENTS IN A CIRCUIT
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Circuit Symbol:
Two ways are:
Combination of Inductances:
1. Serial Combination:
 It is formed when any numbers of inductors are connected in a circuit
end-to-end so that there is only one path for current to flow
 The total or equivalent inductance is always larger than the individual
inductance
 Current is the same anywhere it is measured in a series circuit
Total or equivalent resistance (Leq) can be calculated as,
Leq = L1 + L2 + L3 +…………………
2. Parallel Combination:
 It is formed when two or more inductance are placed side-by-side so that
current can flow through more than one path
 The total or equivalent inductance is always smaller than any individual
resistance
 Voltage is the same anywhere it is measured in a parallel circuit
Total or equivalent resistance (Leq) can be calculated as,
𝟏
𝐋𝐞𝐪
=
𝟏
𝐋𝟏
+
𝟏
𝐋𝟐
+
𝟏
𝐋𝟑
…………….
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DIFFERENCES BETWEEN ACTIVE AND PASSIVE ELEMENTS:
Some of the differences between these elements are described below. Both
contribute a lot to the circuitry and thus to many of the electrical and electronic
revolutions that has taken place but the ways they differ are mentioned below:
ACTIVE
ELEMENTS
PASSIVE
ELEMENTS
control the flow of
electric energy within
the circuit
dissipate or store the
electric energy
does not depend on
other elements for
operations
depends on others for
elements
there should be a
power source for its
working
don't require power
from the supply to
produce its effect on a
signal
active elements cannot
store energy.
Some passive
components also have
the capability to store
energy and release
later
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DESPITE OF THESE DIFFERENCES, ONE CANNOT DENY THE
IMPORTANCE OF ACTIVE AND PASSIVE ELEMENTS IN
TODAY’S LIFE.
THEREFORE, SOME OF THE CONTRIBUTION AND HOW IT
CARRIES WEIGHT ARE DESCRIBED BELOW:
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BIBLIOGRAPHY:
http://en.wikipedia.org/wiki/Power_supplies
http://www.google.com.pk/search?hl=en&site=imghp&tbm=isch&source=hp&biw=1024&bih=630&
q=dependent+sources+in+a+circuit&oq=dependent+sources+in+a+circuit&gs_l=img.3...179.7353.0.7
561.30.18.0.12.12.2.280.2221.9j4j5.18.0...0.0...1ac.1.7.img.4lXT9TJ5FuE
http://www.google.com.pk/search?hl=en&site=imghp&tbm=isch&source=hp&biw=1024&bih=630&
q=dependent+sources+in+a+circuit&oq=dependent+sources+in+a+circuit&gs_l=img.3...179.7353.0.7
561.30.18.0.12.12.2.280.2221.9j4j5.18.0...0.0...1ac.1.7.img.4lXT9TJ5FuE
http://en.wikipedia.org/wiki/Electronic_component
BASIC ELECTRICAL ENGG BY S.N SINGH
AS AND A LEVEL PHYSICS BY DAVID SANG,GRAHAM JONES,RICHARD WOODSIDE AND GURINDER
CHADHA.
http://www.differencebetween.com/difference-between-active-and-vs-passivecomponents/#ixzz2O5BFGRSo
http://www.eie.polyu.edu.hk/~cktse/linear_circuits/main/node6.html
http://www.google.com.pk/#hl=en&sclient=psyab&q=examples+of+independent+sources+in+a+circuits&oq=examples+of+independent+sources+in
+a+circ&gs_l=serp.3.0.33i29i30.2420.7051.0.9122.10.10.0.0.0.0.2874.9209.3-5j61j3j0j1.10.0...0.0...1c.1.7.psyab.zUzaEiILvfk&pbx=1&fp=1&biw=1024&bih=630&bav=on.2,or.r_qf.&cad=b
http://www.electrical4u.com/ideal-dependent-independent-voltage-current-source/
http://wiki.answers.com/Q/What_is_the_Difference_between_active_and_passive_elements
http://www.oocities.org/electricgenerator/
http://en.wikipedia.org/wiki/Transformer
http://www.google.com.pk/search?hl=en&site=imghp&tbm=isch&source=hp&biw=1024&bih=630&
q=op-amp&oq=op-amp&gs_l=img.3..0l8j0i24l2.1968.5246.0.5870.8.8.0.0.0.0.787.1900.0j2j42j0j1.5.0...0.0...1ac.1.7.img.sqezlu2x94c
http://www.google.com.pk/search?hl=en&site=imghp&tbm=isch&source=hp&biw=1024&bih=630&
q=RESISTOR&oq=RESISTOR&gs_l=img.3..0l10.6597.8109.0.8654.8.8.0.0.0.0.410.822.0j1j1j0j1.3.0...0.
0...1ac.1.7.img.f1iJUab2QXg
https://www.google.com.pk/
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