PH6251 PHY2 Notes, Engineering Physics 2 Lecture Notes – IT 2nd SEM Anna University


Anna University Regulation 2013 Information Technology (IT) PH6251 PHY2 Notes for all 5 units are provided below. Download link for IT 2nd SEM PH6251 Engineering Physics 2 Lecture Notes are listed down for students to make perfect utilization and score maximum marks with our study materials.


Conducting materials are classified in to three major categories based on the conductivity.

(i). Zero resistive materials

(ii). Low resistive materials

(iii). High resistive materials

(i)Zero resistive materials

The super conductors like alloys of aluminium, zinc, gallium, niobium, etc., are a special class of materials. These materials conduct electricity almost with zero resistance blow transition temperature. Thus, they are called zero resistive materials.

These materials are used for saving energy in the power systems, super conducting magnets, memory storage elements etc.,

(ii)Low resistive materials

The metals like silver, aluminium and alloys have high electrical conductivity. These materials are called low resistive materials. They are used as conductors, electrical conduct etc., in electrical devices and electrical power transmission and distribution, winding wires in motors and transformers.

(iii)High resistive materials

The materials like tungsten, platinum, nichrome etc., have high resistive and low temperature co-efficient of resistance. These materials are called high resistive materials.

Such a metals and alloys are used in the manufacturing of resistors, heating elements, resistance thermometers.

The conducting properties of solid do not depend on the total number of the electrons available because only the valance electrons of the atoms take part in the conduction. When these valance electrons detached from the orbit they are called free electrons or conduction electrons.

In a metal, the number of free electrons available is proportional to its electrical conductivity. Hence, electronic structure of a metal determines its electrical conductivity.


We know that the electrons in the outermost orbit of the atom determine the electrical properties in the solid. The free electron theory of solids explains the structure and properties of solids through their electronic structure.

This theory is applicable to all solids, both metals and non metals. It explains

(i). The behavior of conductors, semiconductors, and insulators.

(ii). The electrical, thermal and magnetic properties of solids.

So far three electron theories have been proposed.

(i). Classical free electron theory

It is a macroscopic theory, proposed by Drude and Lorentz in 1900. According to this theory, the free electrons are mainly responsible for electrical conduction in metals. This theory obeys laws of classical mechanics.

(ii). Quantum free electron theory

It is a microscopic theory, proposed by sommerfeld in 1928. According to this theory, the electrons in a metals move in a constant potential. This theory obeys laws of quantum mechanics.

(iii). Zone theory or band theory of solids

Bloch proposed this theory in the year 1928. According to this theory, the free electrons move in a periodic potential. This theory explains electrical conductivity based on the energy bands.

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