| 1 |
The magnetism produced by electrons within an atom can arise from |
electrons orbiting the nucleus
electrons orbiting the nucleus
both motions
none one these motions
|
| 2 |
Recently a complex crystalline structure known as Yetrium Barium Copper Oxide have been reported to become superconductor at |
125 K
25 K
263 K
163 K
|
| 3 |
Any superconductor with critical temperature above 77 K, is referred as |
low temperature superconductor
high temperature superconductor
very low temperature superconductor
none of them
|
| 4 |
The critical temperature of lead is |
1.18 K
4.2 K
3.72 K
7.2 K
|
| 5 |
The critical temperature of tin is |
1.18 K
4.2 K
3.72 K
7.2 K
|
| 6 |
The critical temperature of aluminum is |
1.18 K
4.2 K
3.72 K
7.2 K
|
| 7 |
The critical temperature of mercury is |
1.18 K
4.2 K
3.72 K
7.2 K
|
| 8 |
There are some materials whose resistivity becomes zero below a certain temperature, called |
absolute zero
0<span style="color: rgb(84, 84, 84); font-family: arial, sans-serif; font-size: small;">° C</span>
critical temperature
lower fixed point
|
| 9 |
In a semi-conductor material, the total current is |
only the +ve current
only the electronic current
sum of +ve and electronic current
all of them
|
| 10 |
In a semi-conductor material, current flows due to |
positive charge
negative charge
both of them
none of them
|
| 11 |
Whenever a covalent bond is broken in an intrinsic semi-conductor |
hole is created
an electron is created
an electron hole is generated
all of them
|
| 12 |
When a silicon crystal is doped with a trivalent element, then the atom of the trivalent element is known as |
acceptor
donor
either of them
none of them
|
| 13 |
When a silicon crystal is doped with a pentavalent element, then the atom of the pentavalent element is known as |
acceptor
donor
either of them
none of them
|
| 14 |
A hole in a semi-conductor material is treated as |
positive charge
negative charge
neutral
none of them
|
| 15 |
When a silicon crystal is doped with a trivalent element, such an extrinsic semi-conductor is called |
p-type semi-conductor
n-type semi-conductor
either of them
none of them
|
| 16 |
When a sillicon crystal is doped with a pentavalent element, such an extrinsic semi-conductor is called |
p-type semi-conductor
n-type semi-conductor
either of them
none of them
|
| 17 |
Arsenic, antimony and phosphorous are the elements from |
third group
fourth group
fifth group
none of them
|
| 18 |
The bonding between the semi-conductor materials is |
covalent
ionic
either of them
none of them
|
| 19 |
Semi-conductor elements have atoms with |
2 valence electrons
3 valence electrons
4 valence electrons
5 valence electrons
|
| 20 |
The doped semi-conductors materials are known as |
intrinsic semi-conductor
extrinsic semi-conductor
either of them
none of them
|
| 21 |
In the doping process, the ratio of the doping atoms to the semi-conductor atom is |
1 to 10
1 to 10<sup>3</sup>
1 to 10<sup>6</sup>
1 to 10<sup>9</sup>
|
| 22 |
When small number of atoms from some other suitable element is added to the semi-conductor material, then this process is known as |
impurification
adding
doping
extrinsivity
|
| 23 |
A semi conductor in its extremely pure from is known as |
extrinsic semi-conductor
intrinsic semi-conductor
either of them
none of them
|
| 24 |
Conductors are those materials in which energy gap is |
very large (several eV)
very narrow (= 1eV)
either of them
none of them
|
| 25 |
Insulators are those material in which energy gap is |
very large (several eV)
very narrow (= 1ev)
either of them
none of them
|
| 26 |
The materials in which there are plenty of free electrons for electrical conduction are known as |
conductors
insulators
semi-conductors
all of them
|
| 27 |
The materials in which valence electrons are bound very tightly to their atoms and are not free, are known as |
conductors
insulators
semi-conductors
all of them
|
| 28 |
The bands below the valence band are |
completely filled and play active part in conduction process
completely filled and plays no part in conduction process
not completely filled and play active part in conduction process
not completely filled and play no part in conduction process
|
| 29 |
The conduction band in a solid |
may be empty
cannot be empty
should be filled
all of them
|
| 30 |
The electrons occupying the conduction band are known as |
conduction electrons
free electrons
both of them
none of them
|
| 31 |
The band above the valence band is called |
high energy band
conduction band
empty band
none of them
|
| 32 |
The valence band of an atom in a solid |
is always empty
may or may not be empty
can never be empty
none of them
|
| 33 |
When a large number of atoms are brought close to one another to form a solid, each energy level of an isolated atom splits into sub-levels, called |
energy bands
energy shells
states
all of them
|
| 34 |
Electrons of an isolated atom are bound to the nucleus, and? |
can only have distinct energy level
can only have same energy level
may or may not have distinct energy
none of them
|
| 35 |
Which of the following theory completely explain the three types of materials? |
Bohr model of electron distribution
Rutherford atomic model
Pauli's exclusion principle
energy band theory
|
| 36 |
The electrical conductivities of insulators are ranging from |
10<sup>-5</sup>to 10<sup>-10 </sup>(<span style="color: rgb(34, 34, 34); font-family: "Times New Roman"; font-size: 24px; text-align: center; background-color: rgb(255, 255, 224);"><b>Ω m)</b><sup>-1</sup></span>
10<sup>-10</sup>to 10<sup>-15</sup>(<span style="font-family: "Times New Roman"; font-size: 24px; color: rgb(34, 34, 34); text-align: center; background-color: rgb(255, 255, 224);"><b>Ω m)</b><sup>-1</sup></span>
10<sup>-5</sup>to 10<sup>-15</sup>(<span style="font-family: "Times New Roman"; font-size: 24px; color: rgb(34, 34, 34); text-align: center; background-color: rgb(255, 255, 224);"><b>Ω m)</b><sup>-1</sup></span>
10<sup>-10</sup>to 10<sup>-20</sup>(<span style="font-family: "Times New Roman"; font-size: 24px; color: rgb(34, 34, 34); text-align: center; background-color: rgb(255, 255, 224);"><b>Ω m)</b><sup>-1</sup></span>
|
| 37 |
Metals are good conductors of electricity and their conductivities are of the order of |
10<sup>3</sup>(<span style="color: rgb(34, 34, 34); font-family: "Times New Roman"; font-size: 24px; text-align: center; background-color: rgb(255, 255, 224);"><b>Ω m)<sup>-1</sup></b></span>
10<sup>4</sup>(<span style="font-family: "Times New Roman"; font-size: 24px; color: rgb(34, 34, 34); text-align: center; background-color: rgb(255, 255, 224);"><b>Ω m)<sup>-1</sup></b></span>
10<sup>6</sup>(<span style="font-family: "Times New Roman"; font-size: 24px; color: rgb(34, 34, 34); text-align: center; background-color: rgb(255, 255, 224);"><b>Ω m)<sup>-1</sup></b></span>
10<sup>7</sup>(<span style="font-family: "Times New Roman"; font-size: 24px; color: rgb(34, 34, 34); text-align: center; background-color: rgb(255, 255, 224);"><b>Ω m)<sup>-1</sup></b></span>
|
| 38 |
Lead, copper and wrought iron are examples of |
brittle substances
ductile substances
plastic substances
elastic substances
|
| 39 |
Glass and high carbon steel are the examples of |
brittle substances
ductile substances
plastic substances
elastic substances
|
| 40 |
The substances which break just after the elastic limit is reached, are known as |
brittle substances
ductile substances
plastic substances
elastic substances
|