Tuesday, September 06, 2016
S.B. Roll No.______
ELECTRICAL
ENGINEERING MATERIALS
3rd
Exam/Elect/5243/Dec’07
Duration: 3 hrs.
Note: Attempt any five
questions.
1.
a.
Explain how covalent bond result from sharing of
valence electron.
b.
Name two materials used in each as conductors
semi conductors and insulators.
c.
A length of wire has a resistance of 14.5 ohms,
find the resistance of another wire of the same material , three times as long
and twice as big in cross sectional area.
2.
a.
What are the properties that make copper useful
for electrical purposes.
b.
Why is copper being replaced by aluminum now a
days.
c.
Name the materials sue din the making of
i.
Electric kettle element
ii.
Commentator of an electrical machine
iii.
Core of a transformer
iv.
Thermo couples
v.
Power transmission lines
3.
a.
Explain dielectric strength of an insulating
material.
b.
State the factor which affect the dielectric
strength of an insulating material
c.
Mention applications of each of the following
insulating materials
i.
Glass wool
ii.
Bakelite
iii.
Enamel
iv.
PVC
v.
Impregnated paper
4.
a.
Discuss the general properties of plastics.
b.
Explain the use of fillers in plastics.
c.
Explain the usefulness of suiphur hexafluoride
in electrical industries.
5.
a.
How are magnetic materials classified?
b.
Why is the core of electric machines and
transformers made of iron laminations.
c.
Differentiate between soft and hard magnetic
materials.
6.
a.
What are soldering material? How are they
prepared?
b.
Explain the sue of a fuse in electrical system
c.
State the advantages of a cartridge fuse over a
rewire able fuse.
7.
a.
Name the different types of vanishes available and state where they are
used.
b.
Mention two applications of each of the
following:
i.
Platinum
ii.
Mercury
iii.
Tungsten
iv.
Nichrome
8.
Write short note on
a.
Electro thermal break down in dielectrics
b.
Super conductivity
c.
Gaseous insulating materials
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