Detailed Contents
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Classifications of materials
Properties of conductors
Properties of semiconductors
Properties of insulators
Classification based on atomic structure and energy band
Copper and its properties
Aluminium and its properties
High resistivity materials
Superconductors
Semiconductors
Classification of materials
• Classification of Conducting ,semi conducting and insulating
materials based on atomic structure
• Classification of Conducting ,semi conducting and insulating
materials based on energy bands
• A conductor of electricity is a material or substance which
allows to flow of electric current when subjected to a
potential difference Gold ,silver, copper and Aluminium are
conductors.
• A material or an object that does not easily allow heat,
electricity, light, or sound to pass through it. Air, cloth and
rubber are good electrical insulators
• Semiconductor has a conductivity between that of an
insulator and conductor example silicon and germanium
Properties of conductors
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Resistance of conductor is very low or negligible.
The electric filed inside the conductor is zero
The charge density inside the conductor is zero
High conductivity
Casted, forged, rolled, drawn and machined
Malleable and Ductile
Positive temperature coefficient of resistance.
Properties of Semiconductor
• Conductivity lies between conductor and insulator.
• They are negative temperature coefficients of
resistance.
• Resistivity is high
• Adding of impurity result in increased conductivity.
• Small forbidden energy band of 1ev approx.
Properties of Insulators
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High resistance
High dielectric strength
They are rigid , tough and strong
Low permittivity
Low dissipation factor
Least thermal expansion
High thermal strength
Classification based on atomic
structure
Classification based on energy bands
Classification of conducting material as low
resistivity and high resistivity materials
• Low resistance materials Copper, Aluminium, steel,
Silver, Gold, Platinum , copper alloys Brass, Bronze.
• High resistivity materials manganin, constantan,
Nichrome, mercury, platinum, carbon and tungsten
Copper and its properties
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A good electrical conductor
A good thermal conductor
Corrosion resistant
Antibacterial
Easily joined
Ductile
Tough
Non magnetic
Easy to alloy
Recyclable
Catalytic
Properties of Aluminium
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It is silver- white in colour
It posses high ductility
It has high thermal and electrical conductivity
It has high contact resistance
High reflectivity for light rays
It can be rolled into thin sheets and drawn into wires
Copper alloys Brass, Bronze
• An alloy is a combination of metals
• Brass and bronze are both alloys of copper -- that is,
they are ``solid solutions," or mixtures of copper with
another metal.
• The main difference between brasses and bronzes is
that brass is mostly made of copper and zinc while
bronze is mostly made of copper and tin.
High resistivity material properties
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High resistivity.
High melting point.
High mechanical strength.
High ductility, so that can be drawn in the form of
wire easily.
High corrosion resistance mean free from oxidation.
Low cost.
Long life or durable.
High flexibility.
Superconductors and their
applications
• Superconductivity is a phenomenon of exactly
zero electrical resistance when cooled below a
characteristic critical temperature
• Superconducting magnets are used in MRI (Magnetic
Resonance Imaging) which is a way of looking at the
soft
• Low and high field magnets for Nuclear Magnetic
Resonance (NMR) parts of the body.
• Industrial magnets for materials magnetic separation
Semiconductors
• A solid substance that has a conductivity between that of an
insulator and that of most metals, either due to the addition
of an impurity or because of temperature effects
• Most
common
materials
commercially
used
as
semiconductors are germanium (Ge) and silicon (Si) because
of their property to withstand high temperature
• Semiconductors show negative temperature coefficient
• Semiconductor in its pure form is called as intrinsic
semiconductor
• Impure semiconductors are called extrinsic semiconductors
Extrinsic Semiconductors Types
• N-type and P-type semiconductors
• N-type semiconductor majority carriers are electrons
and minority carriers are holes. It is formed by
adding pentavalent impurity e.g. P. As, Sb
• P-type semiconductor majority carriers are holes,
and minority carriers are electrons. These are formed
by adding trivalent impurity e.g. B, Al Ba
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