This document is part of teaching materials for Fundamental of
Electro-system under the Secondary Level School Curriculum
(Technical and Vocational Stream).
This document does not cover all aspects of learning Fundamental of
Electro-system, nor should it be taken as the primary source of
information. The core textbooks and reference materials for learning
the subject have already been specified and provided to the students.
Students are encouraged to study from the original sources, as this
document cannot be used as a substitute for the prescribed textbooks.
Various textbooks as well as freely available material from the internet
were consulted for preparing this document. The contents in this
document are copyrighted to the instructor and the authors of original
texts where applicable.
C@MANISH RAI 2025
Manish Rai
manishraee99@gmail.com
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UNIT - 1
INTRODUCTION TO ELECTROSTATICS
❖ Electrostatic:
Electrostatics is the branch of science that deals with the phenomena of electricity at rest.
❖ Method of Electrification:
When a plastic comb is brought near to the pieces of paper, it does not attract the papers. But
when it is brought nearer after rubbing or combing the hair, it attracts the paper. Similarly,
when a glass rod rubbed with silk cloth is brought nearer to the pieces of paper, the glass rod
will also attract the pieces of paper. From these it can be said that the attracting capacity is
developed on the body due to friction. When the body produces a charge on it, it is said to be
electrically charged or electrified. The process of producing the charge on a body is called
electrification. Sometimes, a crackling sound is heard in the electrification caused by friction.
It can be felt when we take out sweater in dark room. These crackling sounds are due to the
electric sparks.
❖ History of Electricity:
➢ Around 600 BC :
Thales, a Greek Scientist, found that when amber was rubbed with silk, it became
electrically charged and attracted objects. He had originally discovered static electricity.
➢ 1752 :
Ben Franklin (United States) tied a key to a kite string during a thunderstorm, and proved
that static electricity and lightning were the same thing.
➢ 1800 :
The first electric cell was developed by Italian Scientist Alessandro Volta. He put copper
and zinc on opposing sides of a piece of paper that had been soaked in salt water, and he
observed as a chemical reaction created an electric current. He invented the first electric
battery by joining a lot of these cells together. The term volt is named in his honor.
➢ 1821 :
Michael Faraday (England) discovered the principle of electro-magnetic rotation that
would later be the key to developing the electric motor.
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➢ 1878 :
Joseph Swan (England) invented the first incandescent lightbulb (also called an electric
lamp). His lightbulb burned out quickly.
➢ 1879 :
After many experiments, Thomas Edison (United States) invented an incandescent light
bulb that could be used for about 40 hours without burning out.
➢ 1883 :
Nikola Tesla (U.S. immigrant from Austrian Empire) invented the Tesla coil, a
transformer that changed electricity from low voltage to high voltage, making it easier to
transport over long distances.
➢ 1884 :
Nikola Tesla invented the electric alternator for producing alternating current (AC). Until
this time, electricity had been generated using direct current (DC) from batteries.
➢ 1888 :
Nikola Tesla (U.S. immigrant from Austrian Empire) demonstrated the first polyphase
alternating current (AC) electrical system. His AC system included all units needed for
electricity production and use: generator, transformers, transmission system, motor (used
in appliances) and lights.
➢ 1895-96 :
The Niagara Falls hydropower station opened. It originally provided electricity to the local
area.
❖ Types of electricity:
1. Static Electricity
2. Dynamic Electricity (current electricity)
1.Static Electricity
➢ Static electricity results from electrons separating from their atoms.
➢ The accumulation of an electric charge in one place is known as static electricity.
➢ The charge remains stationary and does not move.
➢ Static electricity (the word static means something that does not move) is the term for when
electricity collect in one location.
For Example,
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When a glass rod is rubbed with silk cloth, the charge is produced in it. Similarly, if an ebonite
rod is rubbed with woolen cloth or with fur, it also develops charge in it. These charges
developed in glass rod and ebonite rod are termed as static electricity, as the charges produced
remains at rest i.e, the charges developed do not move. The lightning that we see in the sky
during rainy season also involves static electricity.
2.Dynamic Electricity (current electricity)
➢ Current electricity is another name for dynamic electricity.
➢ In current electricity, the electric charges are in motion i.e the charges move from one point
to another point in a circuit. Due to this, an electric current is produced.
➢ Similarly, the electricity that is produced due to the different sources in a circuit can also
be said as current electricity.
➢ The electricity that we use in our home is an example of current electricity.
➢ The electricity that we use in our home is an example of current electricity. All of the
electrical devices we use, including phones, MP3 players, electric bulbs, and washing
machines, are powered by electric current.
❖ Differences between Static and Dynamic Electricity:
S.N Static Electricity Dynamic Electricity
1 The electricity which is build up on The dynamic electricity is because of
the surface of the substance is known flow of electrons.
as the static electricity.
2 It induced because of the movement of The current electricity is because of the
the negative charges from one object movement of the electrons.
to another.
3 The static electricity develops both in The current electricity develops only in
the conductor and insulator. conductor.
4 It doesn’t induces the magnetic field. It induces magnetic field.
5 It exist for short time. It exist for long time.
6 Gold leaf electroscope is used to Analog and digital meter is used to
measure static electricity. measure dynamic electricity.
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❖ Uses of Electricity:
The uses of electricity in different fields are mentioned as follows below:
Uses of Electricity In Entertainment
The uses of electricity in the entertainment industry are as follows:
o Listening to music on MP3 players and speakers.
o Listening to the radio.
o Watching television for entertainment.
Uses of Electricity In Healthcare
The uses of electricity in the healthcare industry are as follows:
o Operating of healthcare devices.
o Surgical procedures also require electricity.
o Providing high-power light to the doctors so they can see everything clearly while
examining and doing any procedure.
o Working on ventilators, as proper air ventilation is very important for hospitals.
Uses of Electricity As Fuel
o It is used as a renewable source of energy.
o It is a substitute for all the depleting natural resources like coal, petroleum, etc.
o Its usage also does not harm the environment in any way. Get Pas
Unlimited Test Re-Attempts
❖ Uses of Electricity in Daily Life:
The uses of electricity in our daily lives are mentioned as follows below:
Residential Uses of Electricity
o It is used in many electrical household appliances like microwaves, refrigerators, etc.
o It is also used for supplying light to a home.
o It is also used for supplying power in a home.
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Transportation Uses of Electricity
o It is used in public transport systems like the metro, railway lines, etc.
o Nowadays it is also used in many electric vehicles like cars, bikes, etc.
o It is also used to charge batteries used in transportation.
Industrial Uses of Electricity
o It is used to operate motors and machinery which is used in industries.
o It is also used to supply light to industries.
o It is also used to run computers, laptops, and other office equipment.
o It is also used for packaging goods.
o It is also used in providing heat as well as cooling down according to the requirement of
the industry.
o It is also used for providing ventilation to many industries.
❖ Atom and its component:
An atom is the smallest unit of an element, consisting of a nucleus composed of protons and
neutrons, surrounded by a cloud of electrons. The nucleus is positively charged due to the
protons it contains, while the electrons carry a negative charge and orbit around the nucleus in
specific energy levels or shells.
The components of an atom are:
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Nucleus: The central part of an atom, composed of protons and neutrons. Protons have a
positive electrical charge, while neutrons have no electrical charge (they are neutral).
Electrons: Negatively charged particles that orbit around the nucleus in various energy levels
or electron shells. Electrons are much smaller and lighter than protons and neutrons.
Protons: Positively charged particles found in the nucleus of an atom. The number of protons
in the nucleus determines the atomic number of the element, which in turn determines the
identity of the atom.
Neutrons: Neutral particles found in the nucleus of an atom.
In summary, the components of an atom are:
1. Protons: Positively charged particles in the nucleus.
2. Neutrons: Neutral particles in the nucleus.
3. Electrons: Negatively charged particles orbiting the nucleus in electron shells.
❖ Terms related to atom :
1.Atomic number:
The number of protons or number of electrons contained in an atom is known as its atomic
number.
i.e Atomic number = No. of protons or No. of electrons contained in an atom
For example; the number of protons and electrons in oxygen is 8, hence its atomic number is8.
2.Atomic Weight:
The sum of total number of protons and number of neutrons contained in an atom is known as
its atomic weight.
i.e. Atomic weight = No. of protons + No. of neutrons
For example; the number of protons and neutrons contained in oxygen is 8 and 8 respectively
hence its atomic weight is 16.
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3.Free Electrons:
Electron that is not attached to an atom, or molecule and is free to move under the influence of
an applied magnetic field or electric field is known as free electron. Free electrons are those in
an atom that are not bound to nucleus and are thus free to move in response to an external
energy source. The free electron is not affected by the nucleus’s force of attraction.
4.Electrical charges:
The components of an atom form an electric charge. The terms “positive charge” and “negative
charge” refer to two different types of electric charge. Positive and negative charges are generated
by protons and electrons respectively. In general, atoms are electrically neutral due to having the
number of equal number of protons and electrons in an atom. But if some electrons are removed
or added to an atom, then the number of electrons and protons in that condition becomes unequal.
Thus, an atom then develops charge in it. It develops a positive charge on lose of electron and
negative charge on gain of electron.
In brief, it can be said that a body develops a positive charge on deficiency of electron and develops
a negative charge on excess of electrons in it. And this deficiency or excess of electrons in a body
is known as a charge.
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❖ Coulomb’s Law:
Charles Augustin de Coulomb, a French physicist , published Coulomb’s Law.
Coulomb’s Law states that, “the electrostatic force between any two charged body is directly
proportional to the product of the magnitude of these charges and inversely proportional to the
square of the distance between them.”
Let us consider two charges, ‘ q1 ’ and ‘ q2 ’; separated by a distance ‘ r ’. The force of attraction
or repulsion is ‘ F ’.
i.e, Force(F) ∝ q1 .q2 -------------- (i)
1
Force(F) ∝ -------------- (ii)
𝑟2
Combining (i) and (ii)
q1 .q2
F ∝ 𝑟2
q1 .q2
F =k 𝑟2
Where, k = proportionality constant (Coulomb’s constant) whose value is 9 × 109 Nm2/C2.
❖ Electric Field:
The area around the charged object up to which it can attract other charged materials or substances
is known as electric field of that object. Electric field can also be defined as the electric force per
unit charge.
i.e,
𝐅𝐨𝐫𝐜𝐞(𝐅)
Electric Field(Electric Force)=
𝐔𝐧𝐢𝐭 𝐂𝐡𝐚𝐫𝐠𝐞(𝐪)
It’s unit is Newton/Coulomb.
❖ Electric Potential:
The amount of work done needed to move a unit charge from low potential region to a high
potential region against an electric field is called electric potential. It can also be defined as the
work done per unit charge.
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i.e,
𝐖𝐨𝐫𝐤 𝐃𝐨𝐧𝐞(𝐖)
Electric Potential(Voltage)=
𝐔𝐧𝐢𝐭 𝐂𝐡𝐚𝐫𝐠𝐞(𝐪)
It’s unit is Joules/Coulomb (Volt).
❖ Potential Difference:
The amount of work done in moving a unit charge from one point to another point in a circuit is
known as potential difference across two points. Potential difference is also known as Voltage
difference.
The difference between the potential at point A and the potential at point B is defined by the
equation,
Potential Difference (VAB)= VA - VB
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