This document provides an introduction to basic electrical concepts including charge, voltage, current, and circuits. It defines key terms like electricity, voltage, current, and power. It explains how voltage can be produced through different means like friction, pressure, heat, light, chemical reactions, and magnetism. It also defines circuit terminology such as electrical circuit, source, load, network elements, nodes, branches, loops, and meshes. Finally, it lists common units of electrical quantities like the ampere, coulomb, electron volt, faraday, henry, and ohm.

1. UNIT I
FUNDAMENTALS OF ELECTRICITY
AND DC CIRCUITS
BASIC ELECTRICAL,
ELECTRONICS AND
MEASUREMENT ENGINEERING

2. Introduction
 Electricity is an apparent force in nature that exists
whenever there is a net electrical charge between any
two objects.
 Electrical charges are either negative (electrons) or
positive (protons)
 The unit of charge, q , is called the coloumb.
 When there are equal numbers of positive and negative
charges there is no electrical force as there is no net
charge. This is the case for a neutral atom.
 Electrical force is created when electrons are
transferred from one material to another (e.g. rubbing a
wool cloth with a plastic comb).
 Electrical charge is conserved; charge is neither
created nor destroyed

3. Voltage
 A force of attraction exists between positive and
negative charges.
 All charges possess a certain amount of potential
energy.
 The difference in potential energy of the charges
is called potential difference (in electrical
terminology it is known as voltage) – V or v

4. Principal Method of Producing
a Voltage
 Friction - Voltage is produced by rubbing two
materials together.
 Pressure (piezoelectricity) - Voltage is produced by
squeezing crystals of certain substances.
 Heat (thermo-electricity) - Voltage is produced by
heating the joint (junction) where two unlike metals
are joined.
 Light (photo-electricity) - Voltage is produced by light
striking photosensitive (light sensitive) substances.
 Chemical action - Voltage is produced by chemical
reaction in a battery cell.
 Magnetism - Voltage is produced in a conductor when
the conductor moves through a magnetic field or a

5. Current
 If a certain amount of voltage is applied across
the material (semi conductive / conductive) all
free electrons move in one direction depending
on the polarity.
 Movement of electrons from one end to other
constitutes electrical current (I or i)
 The conventional direction of current flow is
opposite to flow of –ve charges/electrons.

6. Power
 Rate of change of energy (P or p)
 Kilowatt-hours, kW-hr = hp x 0.746 kW/hp x
Operating time, hr

7. The Circuit
 The purpose of the circuit is to transfer energy
from sources to the load.
 A closed circuit:- a circuit in which current has a
complete path to flow.
 An open circuit:- the current path is broken , so
that current cannot flow.

8. Network Terminology
 Electric network:-Interconnections of two or
more simple circuit elements (R,L,C). Any
arrangement of electrical energy sources and
circuit elements is called an electrical network.
Electrical energy sources can be batteries and
generators. Circuit elements are resistance
(R), inductance (L), and capacitance (C).

9.  Electrical Circuit: It is a closed path followed by an
electric current. All electrical circuits are electrical
networks. Read about the differences between two
types of the electrical circuit: Series and Parallel
Circuit.
 Source: It is the device that supplies electrical
energy. Example: Battery, Generator.
 Load: It is the device that utilizes electrical
energy. Example: Lamp, Motor, Heater.
 Network elements: It is any circuit element with two
terminals that can be connected to other circuit
elements. Example: Resistors R1, R2, R3 in Figure
 Node: It is a junction where two or more circuit
elements are connected together. Example: Points
1,2,3,4,5,6 in Figure

10.  Minor node: Point at which only two elements
are connected together. Example: Point 1 in
Figure
 Major node: Point at which three or more
elements are connected
together. Example: Points 2,5 in Figure In circuit
analysis, the term node implies only the major
node
 Branch: It is the part of a circuit that lies between
two junction points. Example: 1-2, 2-5, 1-6 in
Figure
 Loop: It is any closed path of a
circuit. Example: 1-2-3-4-5-6, 1-2-5-6, 2-3-4-5 in
Figure
 Mesh: It is the most elementary form of a loop. A

11. Symbol and unit of quantities
 Ampere
 The ampere is the unit of electric current in the SI
 Coulomb
 The coulomb is the unit of electric charge in the
metre-kilogram—second-ampere system, the basis
of the SI system of physical units.
 Electron Volt
 A unit of energy commonly used in atomic and
nuclear physics, the electron volt is equal to the
energy gained by an electron

12.  Faraday
 The faraday (also called the faraday constant) is used in the
study of electrochemical reactions and equal to the amount of
electric charge that liberates one gram equivalent of any ion
from an electrolytic solution.
 Henry
 The henry is a unit of either self-inductance or mutual
inductance
 One henry is the value of self-inductance in a closed circuit or
coil in which one volt is produced by a variation of the inducing
current of one ampere per second.
 Ohm
 The unit of electrical resistance in the metre—kilogram-second
system is the ohm
 It is equal to the resistance of a circuit in which a potential
difference of one volt produces a current of one ampere

13. Thank You