BEE

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Name : G. Snehalatha
Designation : Lecturer
Branch : Electrical & Electronics Engineering
Institute : Govt. Polytechnic, Mahabubnagar
Year/Semester : I Year
Subject : Basic Electrical Engineering
Subject Code : EE105
Topic : Conducting Materials
Duration : 50 minutes
Sub Topic : Introduction to Conducting Materials ,
Hardening and Annealing
Teaching Aids : PPT, Animation, Diagrams
Revised by : A.K.Srikanth, L/EEE, Q.Q.GPT, HYD

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• Understand the classification of electrical engineering
materials based on electronic configuration
• Understand the applications of various electrical
engineering materials.
On completion of this period , you would be able
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Objectives
• Hardening and Annealing
• Understand the effects of Annealing and Hardening on
Copper

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What Type of Conductors used for the
following Applications ?
• House wiring • Copper , Aluminium
• Copper
• Nichrome ,
• ACSR ( Aluminium Conductor
Steel Reinforced )
• Tungsten
• Motor winding
• Electric heaters &
cookers
• Electrical power
transmission
• Filament in bulbs

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Classification of Electrical Engineering
Materials
• Conducting Materials
• Semi Conducting Materials
• Insulating Materials
• Dielectric Materials
• Magnetic Materials
• Special purpose Materials
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Conducting Materials
• Having less than one half (i.e., less than four )
of the maximum of 8 valence electrons
• Ex : Gold, Silver, Copper, Aluminum etc.,
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• House wiring
Applications
• Winding of electrical machines
• Transmission and
•Distribution lines

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Insulating Materials
• Having more than one half ( i.e., More than Four )
of the maximum of 8 valence electrons
• Used to prevent current flow in any path.
• Ex: Rubber , P.V.C , Cotton etc.
Applications
• To isolate the live conductors in all
applications from earth or body
• To isolate the winding from the body in all
electrical machines

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Semi-Conducting Materials
• Having exactly one half ( i.e., Four ) of the
maximum of 8 valence electrons
• Ex: Germanium and Silicon.
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Applications
• In Photo- conductive and Photovoltaic cell
• In Rectifiers and Control circuits
• In Electronic circuits

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• Basically these are insulating materials
• Used to store electrical energy
• Ex: Mica , Paper etc.
Dielectric Materials
• In Capacitors
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Applications

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Magnetic Materials:
• Ex : Iron , Cobalt and Steel etc.
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• Materials that provide path for the magnetic flux
• Materials that forms a medium for energy
conversion in electrical machines
Applications:
• Used in electromagnetic machines,
relays and transformers
• Used in making magnetic circuits

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• Materials used for specific type of application
purpose like safety, protective and relaying.
• Ex : Fuse, Soldering materials etc.
Special purpose Materials:
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Applications
• Switchgear and Protection
• House wiring
• Electronic circuits

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Can we use the pure materials for
desired applications ?
• We Can’t.
• For desired applications, the materials are subjected
to heat treatment process
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• In pure form they are lack in certain properties

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Heat Treatment of Metals
• Heat treatment is given to the metals to change
their mechanical properties
Methods of Heat Treatment
1. Annealing
2. Hardening
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Annealing
• The purpose of annealing is
• To soften the metal
• To relieve internal stresses
• To refine the grains
• To reduce hardness
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Process of Annealing:
• Heating to a predetermined temperature in a furnace
• Holding at this temperature for sufficient time
• Cooling the metal slowly
• By slowly reducing furnace temperature
• By burying it in sand or ash
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Effects of Annealing on Copper:
• Annealing changes mechanical properties of
copper more sharply than its resistivity
• Annealed copper shows
• Good ductility
• Low hardness
• Superior conductivity
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Hardening
• The purpose of hardening is
• To increase the hardness
• To increase wear resistance
• To improve strength
• To improve toughness
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Hardening
• Heating to a predetermined temperature in a furnace
• Holding at this temperature for considerable time
• Cooling the metal suddenly
• By dipping in water or oil
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• The purpose of hardening is

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Effects of Hardening on Copper:
• Hardening changes mechanical properties of
copper
• Hard drawn copper offers
• High mechanical strength
• High hardness
• Hard drawn copper is suitable for
• Contact wires
• Commutator segments
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Summary
In this period we have learnt about
•Electrical engineering materials are classified
based upon their atomic structure
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• Conducting Materials
• Semi Conducting Materials
• Insulating Materials
• Dielectric Materials
• Magnetic Materials
• Special purpose Materials

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• Annealing is to soften the metal
• Hardening is to increase the hardness
• Annealing and Hardening changes
the mechanical properties of copper
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Summary

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Quiz
1.Materials having less than 4 valence electrons
(a) Insulators
(b) Conductors
(c) Semi conductors
(d) None of the above

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2. Materials having more than 4 valence electrons
(a) Insulators
(b) Conductors
(c) Semi conductors
(d) None of the above
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Quiz

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3.Which of the following is a semiconductor
(a) Copper
(b) Germanium
(c) Silver
(d) None of the above
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Quiz

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4. Which of the following is an insulator
(a) Aluminum
(b) Silicon
(c) Rubber
(d) None of the above
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Quiz

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5. Heat treatment is given to the metals to
change their
(a) Electrical properties
(b) Chemical properties
(c) Mechanical properties
(d) None of the above
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Quiz

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6. Annealing is to
(a) Harden the metal
(b) Soften the metal
(c) Increase the resistance
(d) None of the above
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Quiz

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7. Hardening is to
(a) Reduce the hardness
(b) Increase the softness
(c) Increase the hardness
(d) None of the above
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Quiz

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Frequently Asked Questions
1. Classify the electrical engineering materials
2. What type of materials used for the following
purposes
• Filament in bulb
• Rectifier circuits
• Capacitor

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3. What is the necessity of heat treatment of metals.
4.What is Annealing and mention its effects.
5. What is Hardening and state its effects.
Frequently Asked Questions

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