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ELECTRICAL ENGINEERING
MATERIAL LECTURE NOTES
for
Bachelor of Technology
in
Electrical Engineering
&
Electrical and Electronics Engineering
Department of EE & EEE
Veer Surendra Sai University of Technology
(Formerly UCE, Burla)
Burla, Sambalpur, Odisha
Lecture Note Prepared by:
Prof. Ramesh Chandra Prusty

SYLLABUS
ELECTRICAL ENGINEERING MATERIALS (3-1-0)
Credit-04
MODULE-I (10 HOURS)
Conductivity of Metal: Introduction, factors affecting the resistivity of electrical materials,
motion of an electron in an electric field, Equation of motion of an electron, current carried by
electrons, mobility, energy levels of a molecule, emission of electrons from metals, thermionic
emission, photo electric emission, field emission, effect of temperature on electrical conductivity
of metals, electrical conducting materials, thermal properties, thermal conductivity of metals,
thermoelectric effects.
MODULE-II (10 HOURS)
Dielectric Properties: Introduction, effect of a dielectric on the behavior of a capacitor,
polarization, the dielectric constant of monatomic gases, frequency dependence of permittivity,
dielectric losses, significance of the loss tangent, dipolar relaxation, frequency and temperature
dependence of the dielectric constant, dielectric properties of polymeric system, ionic
conductivity in insulators, insulating materials, ferroelectricity, piezoelectricity.
MODULE-III (10 HOURS)
Magnetic properties of Materials: Introduction, Classification of magnetic materials,
diamagnetism, paramagnetism, ferromagnetism, magnetization curve, the hysteresis loop, factors
affecting permeability and hysteresis loss, common magnetic materials, magnetic resonance.
MODULE-IV (10 HOURS)
Semiconductors: energy band in solids, conductors, semiconductors and insulators, types of
semiconductors, Intrinsic semiconductors, impurity type semiconductor, diffusion, the Einstein
relation, hall effect, thermal conductivity of semiconductors, electrical conductivity of doped
materials.
BOOKS
[1] C.S.Indulkar and S. Thiruvengadam, S., “An Introduction to Electrical Engineerin
[2] Kenneth G. Budinski,, “Engineering Materials: Prentice Hall of India, New Delhi

MODULE-I
CONDUCTIVITY OF METALS
INTRODUCTION:
The most important properties of metals are their high thermal and electrical conductivities.
Silver has the highest electrical conductivity. Copper comes next and is similar to silver from the
point of view of atomic structure ; both belonging to the same group of periodic table. The
conductivity of copper is less than that of silver. Since supplies of copper are not abundant in
nature, aluminium which is light and has a high conductivity is rapidly becoming more important
as a conductor material. Gold which has a conductivity higher than that of aluminium but lower
than that of silver or copper does not find use in electrical industry because it is expensive.
Metals having complex structures such as As, Sb, Bi, Sn, Hg have lower conductivities which lie
between those of ideal metal (very high conductivity) and of insulators (negligible
conductivities).
FACTORS AFFECTING THE RESISTIVITY OF ELECTRICAL MATERIALS
1. Temperature : The electrical resistance of most metals increases with increase of
temperature while those of semiconductors and electrolytes decreases with increase of
temperature. Many metals have vanishing resistivity at absolute zero of temperature
which is known as superconductivity.
2. Alloying : A solid solution has a less regular structure than a pure metal. Consequently,
the electrical conductivity of a solid solution alloy drops off rapidly with increased alloy
content. The addition of small amount of impurities leads to considerable increase in
resistivity.
3. Cold Work : Mechanical distortion of the crystal structure decrease the conductivity of a
metal because the localized strains interfere with electron movement.
4. Age Hardening : It increases the resistivity of an alloy.
MOTION OF AN ELECTRON IN AN ELECTRIC FIELD
In a conductor, the electrons are moving about with random velocity , the magnitude of which
depends upon the temperature. There are two comonents of motion, as follows :
1. Random motion , due to thermal effects.
2. Directed motion , the direction being determined by the polarity of the electric field.
EQUATION OF MOTION OF AN ELECTRON
When no electric force is applied , the free electrons move about through the conductor in a
random manner in such a way that the number of electrons moving from right to left is the same
as the number moving from left to right and the resultant current is nil. If an electric force is

applied to the conductor, each electron has superposed on to its random motion, a motion
impressed on it by electric force, and the electrons as a whole are driven through the conductor
by the continued action of this electric force.
THE CURRENT CARRIED BY ELECTRONS
In a current carrying conductor, the electrons drift along with an average velocity which is
generally small compared with their random velocity due to thermal agitation. Let a current I be
carried along a conductor of cross section A by electrons of charge -e and of average drift
velocity v. In time dt the electrons will travel a distance vdt and the number of electrons crossing
any cross section A in time dt will be the number contained in the volume Avdt. Thus if there are
N electrons per unit volume of the conductor the total charge flowing through the section in time
dt is dq= -e.N.A.v.dt
I=dq/dt= -eNAv
And current density
I/A= -e Nv = +e2NEt/m
Since,
v= -eEt/m
The expression for current density shows that the current density does not depend on the size of
the conductor. It is a general property of the material. Finally, the current density is proportional
to the electric field strength and the constant of proportionality e2Nt/m is called conductivity of
the material and is denoted by σ= e2Nt/m .
Ohm’s law follows as an immediate consequence of the relation J= c ; because
I=J.A
= σE.A
= (σV/l).A
Where l is the length of conductor and V is the voltage applied to the conductor ends. Since
σA/l=R where R is the resistance of the conductor.
MOBILITY :
It has been noted that the average drift velocity of the electrons in an applied field is proportional
to the field , the absolute magnitude of the proportionality factor et/m, being called the mobility
of the electrons which is denoted by u. The mobility may thus be defined as the magnitude of
average drift velocity per unit field.
The mobility and the conductivity are related by the equation σ= NeU.
Thus the mobility of the electrons can be determined by knowing the conductivity of the material
and estimating the number of free electrons.
Mobility, U= σ/Ne = 1/ρNe
=1/(1.73x10-8 x8.5x1028x1.6x10-19
=4.25x10-3 m2/volts-sec .
The order of magnitude of collision time for copper atoms may be determined from the relation
t=m/Ne2ρ .
In the absence of an electric field no electric current is observed in the conductor. When an
electric field is applied to the conductor the electrons moving in the direction of the electric force

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