Material Science
Prof. Satish V. Kailas
Associate Professor
Dept. of Mechanical Engineering,
Indian Institute of Science,
Bangalore – 560012
India
Chapter 14. Electrical properties
Engineering materials are important in everyday life because of their versatile structural
properties. Other than these properties, they do play an important role because of their
physical properties. Prime physical properties of materials include: electrical properties;
thermal properties; magnetic properties; and optical properties. The electrical behaviors
of engineering materials are diverse, and so are their uses in electrical applications. Few
examples of electrical applications: copper and aluminium wires used in power
transmission; amorphous silicon in solar cells; LEDs; gallium-arsenide chips used in
modern day computers, cell phones, digital assistants; etc.
This chapter shall describe electrical properties and behavior of engineering materials in
electrical applications. First, basic electrical property, electrical conductivity, will be
described followed by different types of electrical conduction including semi- and super-
conductivities. Some peculiar phenomena like ferro-electricity and peizo-electricity are
explained in addition to electrical insulation.
14.1 Electrical conduction
Electrical conductivity of a material is defined in terms of ease with which a material
transmits an electrical current. Electrical current (I) is flow of electrons, and driving force
for the flow of electrons is called voltage (V). Ohm’s law relates these parameters as
follows:
V α I
V = IR……………………………….………..(1)
where R – is the materials resistance to flow of electrons through it.
V, I, and R respectively have units as volts, amperes, and ohms (Ω).
Electrical resistance of a material is influenced by its geometric configuration; hence a
new parameter called electrical resistivity (ρ) is defined such as it is independent of the
geometry.
l
RA
=
ρ
……………………………..……….(2)
where A – cross-sectional area per