| 1 |
The field of a long bar magnet is like a |
Two pole pieces of magnet
Solenoid
Toroid
None of these
|
| 2 |
The magnetic fields are produced by the |
Moving charges
Bar magnets
Motion of conductor in a magnetic field
All of them
|
| 3 |
The technological uses of superconductors are |
MRI
Magnetic levitation trains
Faster computer chips
All of them
|
| 4 |
High temperature superconductors have temperature |
Above 77 K
Below 77 K
At 77 K
None of these
|
| 5 |
In 1986 a new class of ceramic material was discovered at temperature as high as |
19 K
78 K
108 K
12 K
|
| 6 |
The critical temperature Tc for lead is |
5.4 K
6.3 K
6.9 K
7.2 K
|
| 7 |
The critical temperature T for is |
1.6 K
2.71 K
3.72 K
2.82 K
|
| 8 |
The critical temperature Tc for Aluminium is |
2.1 K
1.1 K
1.18 K
1.19 K
|
| 9 |
The electrical resistance of mercury disappeared below temeprature |
2.1 K
3.4 K
4.1 K
4.2 K
|
| 10 |
The first superconductor was discovered by |
Fermi
Kmaerlinghormes
Weinberg
None of these
|
| 11 |
The first superconductor was discovered in |
1905
1911
19161
1920
|
| 12 |
The current once established, does not require |
Current source
Source of emf
Induced current
None of these
|
| 13 |
In super conductors, once the current is established it exists |
1 day
30 days
indefinitely
None of these
|
| 14 |
In superconductors, the resistance of a material drops to zero and no |
Power is dissipated
Energy is dissipated
Current is dissipated
None of these
|
| 15 |
Super conductor offers no resistance to |
Thermal agitation
Electric current
Induced current
None of these
|
| 16 |
Super conductors are materials like |
Alloys
Ceramic
Semiconductors
a and b
|
| 17 |
Super conductors are the those materials whose resistivity becomes zero below certain temperature called |
Curie temperature
Fixed temperature
Critical temperature
None of these
|
| 18 |
In semiconductor Si or Ge a missing electron in covalent bond from an atom is a |
Charged atom
Hole
Ion
All of them
|
| 19 |
When a silicon crystal is doped with trivalent impurity which are |
Indium
Arsenic
Phosphorous
None of these
|
| 20 |
When a silicon crystal is doped with pentavalent impurity which are |
Boron
Antimony
Gallium
None of these
|
| 21 |
The each atom of pure Ge or Si shares neighboring electrons are |
Three
Four
Five
None of these
|
| 22 |
Doping is the process in which the small amount of impurity is added into pure semiconductor lattice in the ratio |
1 to 10<sup>3</sup>
1 to 10<sup>4</sup>
1 to 10<sup>5</sup>
1 to 10<sup>6</sup>
|
| 23 |
The electrical behavior of semiconductor depends on the material purity which is |
Sensitive
Extremely sensitive
Non-sensitive
None of these
|
| 24 |
A semiconductor in its extremely pure form in known as |
Extrinsic semiconductor
Intrinsic semiconductor
Both a and b
None of these
|
| 25 |
Semiconductors, like Ge or Si at room temperature becomes a |
Semiconductor
Conductor
Insulator
None of these
|
| 26 |
The valency of electron in the valence band is known as |
Atom
Molecule
Hole
None of these
|
| 27 |
At 0 K a piece of Ge and Si is a perfect |
Conductor
Insulator
Semiconductor
None of these
|
| 28 |
In semiconductors at 0 K the valence band is |
Completely filled
Partially filled
No
Yes
|
| 29 |
In semiconductors, at 0 K, the electrons in conduction band is |
Partially filled
No
Yes
None of these
|
| 30 |
The energy gap between conduction band and valence band is semiconductor is |
A very narrow forbidden energy gap
A narrow forbidden gap
Of the order of 1 eV
a and b
|
| 31 |
In semiconductors, the valence band at room temperature is |
Completely filled
Partially filled
Empty
None of these
|
| 32 |
In terms of energy bands, semiconductors are those materials which at room temperature have conduction band |
Partially filled
Full filled
Slightly filled
None of these
|
| 33 |
Is there any physical distinction between the valence and conduction band |
Yes
No
Very small
None of these
|
| 34 |
In conductors, the valence band and conduction bands are |
Touch each other
Overlapped each other
Largely overlapped
None of these
|
| 35 |
Conductors are those materials in which the free electrons |
Very large
Very small
Plenty of
None of these
|
| 36 |
The energy gap is insulators becomes very large and has the value |
Few electron volt (eV)
Some electron volt (eV)
Several electron volt (eV)
None of these
|
| 37 |
In Insulators the conduction band is |
Empty
Partially filled
Full
None of these
|
| 38 |
Insulators are those materials in which valence band is |
Empty
Partially filled
Full
None of these
|
| 39 |
Insulators are those materials which valence electrons are bound |
Loosely
Tightly
Very tightly
None of these
|
| 40 |
The conduction of electrons takes place and conduct electric current through solids is a |
Energy band
Conduction band
Valence band
Completely filled band
|