Vacuum may be used for reflective insulation of liquid O2 tank
Permissible water content in transformer oil is 50 ppm
Carbon-pile resistors for insulation of oil-filled cables
Q.2.Memory of a computer can be increased by
increasing the magnetic bubble diameter
decreasing the magnetic bubble diameter
using adomax, a recent hard magnetic material
using strontium titanate (Sr Ti O3)
Q.3.The residual magnetic flux density is more in
metallic magnets
ceramic magnets
graphite
iron oxide
Q.4.Manganese ferrites is a 1:1 mixture of
MnO and CdO
MnO and Fe2O3
MnCl2 and Fe2O3
MnCl2 and CdO
Q.5.High frequency transformer cores are generally made of
Cast iron
Mumetal
Ferrite
Graphite
Q.6.For high speed reading and storing of information in a computer, the use is made of
ferrite
piezoelectric
pyroelectrics
ferromagnetics above 7680 C
Q.7.The poles of alternators are usually made of
wrought iron
permalloy
CdS
alnico
Q.8.In a semi-conductor strain gauge, the change in resistance on application of strain is mainly due to the change in its
lenght
diameter
resistivity
length and diameter
Q.9.Transformer oil is a liquid insulator and is mainly used in transformer.It is filled into transformer tank to serve the following purposes: I. To transfer the heat generated inside the transformer core and windings, to the outer cooling surfaces. II. To main insulation in the primary and secondary windings.
Only I is correct
Only II is correct
Both I and II are correct
None of these
Q.10.Electrons in an atom may be visualized by
spectroscopic techniques
radiography
optical microscope
etching techniques
Q.11.Most malleable metal is
Au
Ag
Cr
Osmium
Q.12.As the temperature of a p-type semi-conductor is gradually and continuously increased, the fermi level will move
into the valence band
into the conduction band
towards the middle of the forbidden gap
into the region between the acceptor level and the valence band
Q.13.Which one of the following polarization mechanisms/sets of mechanisms contribute to the static dielectric constant of a homo-polar neutral dielectric?
Electronic
Electronic and ionic
Electronic, ionic and dipolar
Electric and dipolar
Q.14.Consider the following materials: 1. Pure silica 2. Bakelite 3. Hard rubber 4. Paraffin The correct sequence of the DECREASING order of loss angles (60 Hz) of these dielectric materials is
1,2,3,4
1,4,3,2
4,1,2,3
4,3,1,2
Q.15.Which one of the following materials is piezoelectric?
Pb2 Au
BaTiO3
MgAl2O4
NiFe2O4
Q.16.The residual resistivity of metals
is essentially independent of temperature
increases linearly with increasing temperature
decrease linearly with increasing temperature
initially increase linearly with temperature and then remains constant
Q.17.Consider the following metals:1. Zinc2. Gold3. Silver4. CopperThe correct sequence of the increasing order of their resistivities is
4,3,1,2
3,4,2,1 (Ans)
4,3,2,1
3,4,1,2
Q.18.A type-I super-conductor maintained at a temperature T < Tc is subject to a magnetic field H < Hc. The superconductor will exhibit.
perfect diamagnetism
partial diamagnetism
perfect paramagnetism
partial paramagnetism
Q.19.The magnetic susceptibility of a paramagnetic material is
less than zero
less than one but positive
greater than one
equal to zero
Q.20.Magnetostriction is a phenomenon whereby the magnetisation of a ferromagnetic material leads to a change in
relative permeability
physical dimensions
spontaneous magnetisation
magnetic susceptibility
Q.21.Two initially identical samples A and B of pure germanium are doped with donors to concentrations of 1*1020 m-3 and 3*1020 m-3 respectively. If the hole concentration in A is 9*1012 m-3, then the hole concentration in B at the same temperature will be
3*1012 m-3
7*1012 m-3
11*1012 m-3
27*1012 m-3
Q.22.Consider the following statements :Pure germanium and pure silicon are examples of1. Direct band-gap semi-conductors2. Indirect band-gap semi-conductors3. Degenrate semi-conductorsof these statements
1 alone is correct
2 alone is correct
3 alone is correct
1 and 3 are correct
Q.23.Consider the following statements : In a semi-conductor, the measurement of Hall co-efficient provides quantitative information on1. Density of carriers2. Polarity of carriers3. Effective mass of the carriers4. Mobility of the carriersOf these statements :
1 and 2 are correct
2 and 3 are correct
1 and 3 are correct
1,2,3 and 4 are correct
Q.24.Silicon carbide reinforced aluminum metal matrix composites find application in
the manufacture of transformer cores
the manufacture of cutting tools
the manufacture of standard resistors
aerospace industry
Q.25.GaAs LEDs emit radiation in the
ultra-violet region
violet-blue-green range of the visible region
visible region
infra-red region
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