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KTU S1 & S2 Electronics Engineering Module 1 Full Notes
Evolution of electronics
The word 'electronics' is derived fromelectron mechanics, which means the study of the behavior of an electron under different conditions of
externally applied fields. The Institution of Radio Engineers (IRE) has given a standard definition of electronics as "that field of science and engineering, which deals
with electron devices and their utilization."
Applications of electronics
Electronics play a major role in almost every sphere of our life. The main applications of electronics are as follows.
Communication and Entertainment
In communication, the main application of electronics was in the field of telegraphy and telephony. This utilizes a pair of wires. However, it is now possible with the help
of radio waves to transmit any message from one place to another, thousands of kilometers away, without any wires. With such wireless communication (radio
broadcasting), people in any part of the world can know what is happening in other parts.
Radio and TV broadcasting provide a means of both communication as well as entertainment. With the help of satellites it has become possible
to establish instant communication between places very far apart.
Defense Applications
One of the most important developments during World War II was the RADAR. By using radar it is possible to detect and find the exact location of the enemy
aircraft.The anti­aircraft guns directed to shoot down the aircraft. The radar and anti­aircraft guns can be linked by an automatic control system to make a complete unit.
RADAR
Guided missiles are completely controlled by electronic circuits. In a war, success or defeat for the nation depends on the reliability of its communication system.
Industrial Applications
Use of automatic control systems in industries is increasing day by day. Electronic circuits are used in industrial applications like control of thickness, quality, weight and
moisture content of a material. It is also used in automatic door­openers, lightning systems, power systems and safety devices.
Medical Sciences
Doctors and scientists are constantly finding new uses for electronic systems in the diagnosis and treatment of various diseases. Some of the instruments which have
been in use are:
X­rays, for taking pictures of internal bone structures and also treatment of some diseases
Electrocardiographs (ECG), to find the condition of the heart of a patient.
Short­wave diathermy units, for healing sprains and fractures.
Oscillographs for studying muscle action.
Instrumentation
Instrumentation plays a very important role in any industry and research organization,for precise measurement of various quantities. e,g. VTVM, CRO, frequency
counters, pH­meters,strain­gauges,etc.
CRO ELECTRONIC COMPONENTS
Electronic components are mainly classified into two types they are:
Passive components
Active components
Passive Components
Resistors, capacitors and inductors are called passive components. These components are themselves not capable of amplifying or processing an electrical signal. But,
these components are very important in a electronic circuit. Without aid of these components active components (such as transistor) cannot be made of amplify signal.
Resistor
The flow of charge through any material produce an opposing force. This opposing force is called resistance of the material.
Resistor
Resistor symbol
A resistor is a passive electronic component that offers a specific amount of electrical resistance to the flow of current when connected in a circuit. Unit of resistance is
ohm ( Symbol Ω ). Ohm is a very small unit. Most practical resistors have resistance in thousands or hundred of thousands of ohm. Therefore resistance is often
measured in kilo and mega­ohms.
Color coding of resistors
Carbon resistors are color coded. Carbon resistors are very small size, it is difficult to write the oh­mic values as numbers so color coding is used. Each color has
specific numerical values, this help to find the value of the resistor.
The color bands are read from left to right. The first and second bands represent significant digits respectively of the resistance value. The third band shows the
multiplier value. The fourth band gives the tolerance value.
Types of Resistors
According to the operating conditions the resistors are broadly classified into two types they are;
Fixed Resistors Variable ( or Adjustable) Resistors
Fixed Resistors : Resistors whose oh mic values remains at a constant value are known as fixed resistors.
Fixed resistor symbol used in circuit diagrams
Fixed resistor symbol
Fixed type resistors are further classified as: Wire wound resistors
Carbon composition resistors
Carbon film resistors
Metal film resistors
Variable Resistors : In a variable resistor the resistance value can be varied over a specified resistance range. Variable resistors are classified as:
Potentiometers
Rheostats
Potentiometer
Capacitors
Capacitor is a physical device which is capable of storing energy by virtue of a voltage existing across it. Capacitor store energy in electrostatic fields. A capacitor
consists of two conducting plates separated by an insulating material, The insulating material is known as dielectric. Capacitance is measured by the ability of capacitor
to store charge. Capacitance is measured in farads (F). Practical capacitors are measured in micro­farads (µF) and pico­farads (pF). There are two types of capacitors
fixed capacitor and variable capacitors.
Fixed Capacitors
In fixed capacitors their capacitance value cannot be varied mechanically or by any external means. In fixed capacitors the dielectric is permanently kept in between two
fixed plates. Commonly used fixed capacitors are :
Paper capacitor
Ceramic capacitor
Mica capacitor
Electrolytic capacitor
Paper capacitor
Paper capacitor
It is made of tissue or cellulose paper called Kraft paper.
The Kraft paper is sandwiched between two aluminum foils, which act as conducting parallel plates.
The entire unit is rolled to form a cylinder.
The external connections are soldered on to the aluminum foils and the whole unit is covered with wax coating.
Ceramic Capacitor
Ceramic capacitor
It has made in many shapes and sizes.
The ceramic disc is coated with copper or silver, These coatings acts as the two plates.
The entire unit is coated with plastic and mark its capacitance value.
Mica Capacitor Mica capacitor
Mica capacitors are constructed from plates of aluminum foil separated by sheets of mica.
The plates are connected to two electrodes.
Mica capacitors have excellent characteristics under stress of temperature variations and high voltage applications.
Electrolytic Capacitors
Electrolytic capacitor
Electrolytic capacitors have very high capacity in very small volume.
It has lower cost per micro­farad.
This capacitor will works only under dc potential.
It is used as a bypass capacitor in amplifiers.
Inductors
Inductors
Inductor are long stretches of wires wound in some specific manner over an insulating former that may or may not carry a core inside it. Inductors are further classified
into two types fixed and variable.
Fixed inductor
Variable inductor
Fixed Inductors : It offer a fixed inductance when connected in an electrical circuit. There is no method to alter the inductance.
Variable Inductors : Its inductance value can be changed over a specified range as and when required. The inductance is usually varied by changing the position of
the core with respect to the winding.
Transformer
Transformer is a static device which transforms electrical energy from one circuit to another without any direct electrical connection. It transforms the electrical energy
with the help of mutual induction between two windings. It transforms power from one circuit to another without change in frequency, but the voltage may be in different
levels.
Principle of Operation Transformer works on the principle of mutual induction between two coils lined by a common magnetic flux. The two windings are electrically
separated from each other but they are magnetically coupled. The two windings are wound on same core. The coil which source is given is called primary and the coil
to which load is applied is called secondary.
When A.C supply is given to the primary winding , an alternating flux is produced in it. The alternating flux in the primary
winding links with the secondary winding through core. The alternating flux in the secondary winding produces an e.m.f in it called mutually induced emf. If secondary
circuit is shorted a current will flow through the secondary circuit. When number of turns in secondary is more than that in primary, it is called a step up
transformer.When number of turns in secondary is less than that in primary, it is called step down transformer. In a step up transformer output voltage is more than its
input voltage and in a step down transformer output voltage is less than its input voltage.
Types of Transformers Transformers are classified into several types based on primary and secondary coils arrangement around core, phases and voltage level. According to them,
transformers can be classified into two: 1. Core­ Type Transformer
Core type transformers are popular in High voltage applications like Distribution transformers, Power transformers, and obviously auto
transformers.
2. Shell­Type Transformer
Where as, Shell type transformers are popular in Low voltage applications like transformers used in electronic circuits and power
electronic converters etc.
Relays and Contactors
RELAYS A relay is a switch that is turned on or off using electricity. Relays allow a low­power signal to control a large amount of power. Most relays work by energizing a small
electromagnet which causes the contacts of a switch to close, as shown below.
Here, passing a small current through the coil causes the iron core to become magnetized; the magnetized iron core attracts an iron mass attached to the movable
contacts, causing the contacts to close. Relays are designed so that a SMALL current flowing through the coil leads switches a LARGER current through the contact
leads. There are many different types of relays (not all use electromagnets). We will use the relay shown below (enclosure is cut away).
Contactors
A contactor is a relay which is capable of switching largeelectrical loads. Contactors and relays are operated by applying a voltage to the coil of an Electro­magnet,
which will cause a switch to close. The circuit that applies the voltage to the coil is referred to as the control circuit, because it controls the main device that the
contactor or relay is switching.