01․ ________ is the most detrimental impurity in
the magnetic materials
Carbon.
Sulphur.
Oxygen.
Nitrogen.
02․ How many classes of insulating materials are
there?
6.
7.
5.
8.
03․ What are insulating materials that can
tolerate maximum temperature?
Mica.
Porcelain.
Glass.
All
of these.
04․ What is the value of dielectric constant of
air?
Less
than 1
0.
1.
none
of these.
05․ Which of the following is the example for
piezo-electric material ?
Lead
zirconate titanate
Copper
Potassium
niobate
None
of the above
Zinc
silicate.
Calcium
silicate.
Zinc
sulphide.
Magnesium
silicate.
07․ Which of the following is the least desired
property in magnetic materials for electrical engineering applications ?
High
magnetic permeability.
High
electrical resistivity.
Large
hysteresis loop.
All
of the above.
08․ The magnetisation and applied field in
ferromagnetic materials are related
sinusoidally.
non
linearly.
linearly.
parabolically.
09․ The materials which exhibit the same elastic
properties in all directions are called
isotropic.
isentropic.
inelastic.
visco
elastic.
10․ The dielectric strength of ferroelectric
materials depends to a large extent on
area
of hysteresis loop for the material.
presence
of magnetic materials in the vicinity.
intensity
of electric field.
frequency
of applied voltage.
11․ The potential gradient across the material of
low permittivity is ______________ than across the material of high
permittivity.
greater.
smaller.
both
(A) and (B).
none
of above.
12․ Materials which lack permanent magnetic
dipoles are called
dia-magnetic.
ferro-magnectic.
semi-magnetic.
none
of the above.
13․ Which of the following is the ferroelectric
material ?
Rochelle
salt.
Potassium
dihydrogen phosphate.
Barium
titanate.
All
of the above.
14․ Materials having a high dielectric constant,
which is non-linear, are known as
elastomers.
ferroelectric
materials.
super
die-electrics.
hard
die-electrics.
15․ In ferromagnetic materials
the
atomic magnetic moments are antiparallel and unequal.
the
atomic magnetic moments are parallel.
the
constituent is only iron.
one
of the constituent is iron.
16․ A material with unequal anti-parallel atomic
magnetic moments is
ferrimagnet.
an
anti-ferromagnet.
a
ferrite.
non-magnetic.
17․ The permanent magnets are made from which of
following materials ?
Soft
iron.
Ferromagnetic.
Paramagnetic.
Diamagnetic.
18․ Indicate which of following material does not
retain magnetism permanently
soft
iron.
stainless
steel.
hardness
steel.
none
of above.
19․ Which statement is not true of ferromagnetic
materials.
Energy
loss is proportional to the area of hysteresis loop.
They
have fixed value of μr.
They
have large magnetic susceptibility.
They
lose their nonlinearly property above the Curie temperature.
20․ Which of following material has least value
of dielectric constant?
Paper.
Oil.
Ceramics.
Glass.
21․ In order to minimise
loss due to hysteresis, the magnetic material should have
high
resistivity.
low
hysteresis coefficient.
large
B-H loop area.
high
retentivity.
22․ In electrical
machines the material preferred for pole shoes of electromagnets is
copper.
aluminium.
pure
iron.
lead.
23․ Which of the
following gives materials in order of decreasing values of permeability?
Permalloy,
nickel, air, water.
Cobalt,
nickel, aluminium, iron.
Pure
iron, silicon iron, aluminium, bismuth.
Silver,
copper, aluminium, iron.
