Lec of Basic Electronics for Physics Students or anyone

1. By: Engr. Sundas Islam Page 1 of 5
Lec-1: Basic Electronics. By: Engr. Sundas Islam
1.1 What is Engineering?
Engineering itself is a process to carry out sub-processes of designing, operating, controlling & optimizing.
1.2 Fields of Engineering that deals with flow of Electrons
Electrical Engineering is the father of Electronic Engineering. Electronic engineering can be
differentiated from Electrical engineering in following aspects.
Attribute Electrical Engineering Electronic Engineering
Definition
Electrical engineering deals with
generation, transmission & distribution
of electrical power & its utilization.
Electrical engineering is defined as
anything relating to or concerned with
electricity.
Electronic engineering is a science &
technology that is concerned with the
development & applications of
electronic devices which deal with
current conduction through a vacuum,
gas or semiconductor.
Behaviour
Electrical devices mainly change current
into other form of energy such as heat
or light.
Electronic devices manipulate current in
such a way that it can do a particular
task.
Relation
It is related to producing or being
operated by electricity.
It is concerned with the applications of
electronic devices involving flow of
current.
Data Manipulation
Electrical devices do not manipulate
data.
Electronic devices manipulate data to
assign meaning to it.
Current
Electrical devices use alternating
current (AC).
Electronic devices use direct current
(DC).
Voltage Electrical devices work on high voltages. Electronic devices work on low voltages.
1.3 Direct Current and Alternating Current
1. Alternating Current (ac) periodically reverses in direction as the voltage source (applied voltage)
periodically reverses in polarity. OR the current that changes its direction as the applied voltage
changes its polarity.

2. By: Engr. Sundas Islam Page 2 of 5
When voltage having different polarities is applied to an electronic circuitry then its outcome would be an
alternating current flowing across the circuitry.
1. Direct Current (dc) a current flow that has just one direction because the voltage source (applied
voltage) has fixed polarities.
When voltage having fixed polarity is applied to an electronic circuitry then its outcome would be either
steady voltage and current across the circuitry OR it would be pulsating DC voltage and current across the
circuitry.
1.4 Application of Electronics
1. Rectification: The conversion of a.c. into d.c. is called rectification. Electronic devices can convert a.c.
power into d.c. power with very high efficiency.
For example, Diode, DC supply which can be used for charging batteries, or can be used for supplying
DC voltage to electronic circuitry.
2. Amplification: The process of raising the strength of a weak signal is known as amplification. Electronic
devices that perform amplification are amplifiers.
For example, Amplifier are used in radio sets where the weak signals are amplified so that it can be
heard loudly. Similarly, amplifiers are used in public address system, television etc.

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3. Control: Electronic devices find wide applications in automatic control.
For example, speed of a motor, voltage across a refrigerator etc. can be automatically controlled with
the help of such devices.
4. Generation/Oscillation: Electronic devices are capable of converting d.c. power into a.c. power of any
frequency.
For Example, Electronic device performing this function is known as oscillators. The oscillators are used
in a wide variety of ways.
5. Conversion of light into electricity: Electronic devices can convert light into electricity. This conversion
of light into electricity is known as photo-electricity.
For Example, Photo-electric devices are used in Burglar alarms, sound recording on motion pictures
etc.
6. Conversion of electricity intolight: Electronic devices can convert electricity into light.
For Example, This valuable property is utilized in television and radar.
1.5 Most Commonly used Electronic Components
Electronic components are categorized as being active or passive. Both are generally used together to
form complete circuits in all types of electronic equipment.
1. Passive components can control energy, but they cannot modify it.
E.g: Resistors, Capacitors and inductors.
a. Resistors:
 Resistors are perhaps the most common component in electronic circuit.
 The main function is to limit the flow of current or reduce voltage in a circuit.
 Resistance is the measure of the degree to which a conductor opposes an electric
current passing through it. It is measured in ohms Ω
Type of Resistors Schematic Symbol Notes
Fixed Resistor
provides fixed amount of
resistance.
Some fixed resistors are color
coded to indicate their
resistance value, while others
have their resistance values
printed on the body.
Variable Resistor
whose resistance keeps on
changing.
Potentiometer
- Has three end points /
terminals.
- Varies Voltage.
Rheostat - Has two end points /
terminals.

4. By: Engr. Sundas Islam Page 4 of 5
- Varies Current.
b. Capacitors:
• A capacitor is a component that is able to hold or store an electric charge.
• It consists of 2 metal plates separated by an insulator or free space.
• It blocks direct current and passes alternating current.
• Capacitance is the ability of a body to store an electrical charge. A material with a large
capacitance holds more electric charge at a given voltage, than one with low
capacitance. The basic unit of capacitance is farad (F).
Type Schematic Symbol Notes
Fixed
provides fixed amount of
capacitance.
Stores electric charge.
Blocks dc, passes ac.
Electrolytic
Either one of the metal plates is
oxidized to make it polar or
both the metal plates are
oxidized to make it non-polar
(bipolar).
- Has large
capacitance
- May be polar, non-
polar(bipolar)
- Fixed values only
Variable
whose capacitance keeps on
changing.
Used for tuning radios, TVs,
and other electronic
communications equipment.
c. Inductors:
• Its physical construction is simply a coil of wire. And often called coils.
• They are opposite of capacitors in that they are able to pass a dc current and blocks ac
current.
• Inductance is the property of an electrical conductor by which a change in current
flowing through it induces an electromotive force in both the conductor itself and in any
nearby conductors. It is measured in Henry (H).
Type Schematic Symbol Notes
Air
has air in between the coils
- Induce voltage when
current changes.
- Passes dc and limits ac.
Iron Core
has iron in between the
windings.
- Use for low frequency.

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Variable
whose inductance keeps on
changing.
- Used for tuning radios,
TVs and other
electronic
communication
equipment.
2. Active components are capable of changing energy from one form to another form. Such components
perform process of rectification / amplification.
E.g: diodes and transistors.
a. Diode:
 A diode is an electronic component which allows current to flow through it in one
direction.
 It changes ac voltage to pulsating dc.
b. Transistors:
 An electronic component that can be used to amplify small ac signals or switch to dc
voltage.
 Bipolar Junction Transistor(BJT) is used for amplification.
 Field Effect Transistor FET is used for switching purpose commonly used in ICs
(Integrated Circuit).