Delhi University Entrance Test (DUET) 2019 PhD in Electronics Previous Queston Papers
2)
3)
4)
DU PhD in Electronics
Topic:- DU_J19_PHD_ELEC
An electron beam with 3 eV energy strikes a crystal of cadmium sulfide (CdS) (bandgap E
g
=2.45
eV). Electrons scattered by the crystal move at a velocity of 4.4 ? 10
5
m/s. The scattered energy (in
eV) of the electrons is
[Question ID = 14763]
1. 0.55 eV [Option ID = 29050]
2. 1 eV [Option ID = 29049]
3. 1.45 eV [Option ID = 29051]
4. 0.05 eV [Option ID = 29052]
Correct Answer :-
1 eV [Option ID = 29049]
An ideal photodiode is made of a material with a bandgap energy of 2.35 eV. It operates at 300 K
and is illuminated by monochromatic light with wavelength of 400 nm. Its maximum efficiency is
[Question ID = 14772]
1. 80% [Option ID = 29088]
2. 25% [Option ID = 29085]
3. 75.7% [Option ID = 29086]
4. 48% [Option ID = 29087]
Correct Answer :-
25% [Option ID = 29085]
If line A of X-ray beam gives a first order reflection maxima at a glancing angle of 30? to the
smooth face of a crystal and line B of ? = 0.92 ? gives a third order reflection maxima at an angle 60?
from the face of same crystal, then the wavelength of line A is
[Question ID = 14769]
1. 3.36 ? [Option ID = 29073]
2. 6.72 ? [Option ID = 29076]
3. 0.84 ? [Option ID = 29075]
4. 1.59 ? [Option ID = 29074]
Correct Answer :-
3.36 ? [Option ID = 29073]
If ? = Kein? then the value of ?K? after normalization in the limits 0 to is
[Question ID = 15449]
FirstRanker.com - FirstRanker's Choice
1)
2)
3)
4)
DU PhD in Electronics
Topic:- DU_J19_PHD_ELEC
An electron beam with 3 eV energy strikes a crystal of cadmium sulfide (CdS) (bandgap E
g
=2.45
eV). Electrons scattered by the crystal move at a velocity of 4.4 ? 10
5
m/s. The scattered energy (in
eV) of the electrons is
[Question ID = 14763]
1. 0.55 eV [Option ID = 29050]
2. 1 eV [Option ID = 29049]
3. 1.45 eV [Option ID = 29051]
4. 0.05 eV [Option ID = 29052]
Correct Answer :-
1 eV [Option ID = 29049]
An ideal photodiode is made of a material with a bandgap energy of 2.35 eV. It operates at 300 K
and is illuminated by monochromatic light with wavelength of 400 nm. Its maximum efficiency is
[Question ID = 14772]
1. 80% [Option ID = 29088]
2. 25% [Option ID = 29085]
3. 75.7% [Option ID = 29086]
4. 48% [Option ID = 29087]
Correct Answer :-
25% [Option ID = 29085]
If line A of X-ray beam gives a first order reflection maxima at a glancing angle of 30? to the
smooth face of a crystal and line B of ? = 0.92 ? gives a third order reflection maxima at an angle 60?
from the face of same crystal, then the wavelength of line A is
[Question ID = 14769]
1. 3.36 ? [Option ID = 29073]
2. 6.72 ? [Option ID = 29076]
3. 0.84 ? [Option ID = 29075]
4. 1.59 ? [Option ID = 29074]
Correct Answer :-
3.36 ? [Option ID = 29073]
If ? = Kein? then the value of ?K? after normalization in the limits 0 to is
[Question ID = 15449]
5)
6)
7)
1. [Option ID = 31794]
2. [Option ID = 31793]
3. [Option ID = 31795]
4. [Option ID = 31796]
Correct Answer :-
[Option ID = 31793]
In a microwave test bench, a dip is shown on the CRO display by rotating the micrometer of
wavemeter, which indicates
[Question ID = 14785]
1. frequency of microwave signal is not same as frequency of wavemeter [Option ID = 29139]
2. frequency of microwave signal is zero [Option ID = 29137]
3. frequency of microwave signal is same as frequency of wavemeter [Option ID = 29138]
4. no signal propagates [Option ID = 29140]
Correct Answer :-
frequency of microwave signal is zero [Option ID = 29137]
In a p-type Si sample the hole concentration is 8 ? 10
15
/ cm
3
. The intrinsic carrier concentration
is 4 ? 10
10
/ cm
3
. The electron concentration is
[Question ID = 14766]
1. zero [Option ID = 29061]
2. 4 ? 10
10
/cm
3
[Option ID = 29062]
3. 1.5 ? 10
25
/cm
3
[Option ID = 29063]
4. 2 ? 10
5
/cm
3
[Option ID = 29064]
Correct Answer :-
zero [Option ID = 29061]
Sigma Electronics sells a microwave receiver (A) having an operating spot noise figure of 10 dB
when driven by a source with effective noise temperature 130 K. Deltalink (B) sells a receiver with a
standard spot noise figure of 6 dB when driven by a source with effective noise temperature 190 K.
Zebrotronics (C) sells a receiver with standard spot noise figure of 6 dB when driven by a source with
effective noise temperature 290 K. The best receiver to purchase is
[Question ID = 14782]
1. (A) [Option ID = 29125]
2. None [Option ID = 29128]
3. (C ) [Option ID = 29126]
4. (B) [Option ID = 29127]
Correct Answer :-
FirstRanker.com - FirstRanker's Choice
1)
2)
3)
4)
DU PhD in Electronics
Topic:- DU_J19_PHD_ELEC
An electron beam with 3 eV energy strikes a crystal of cadmium sulfide (CdS) (bandgap E
g
=2.45
eV). Electrons scattered by the crystal move at a velocity of 4.4 ? 10
5
m/s. The scattered energy (in
eV) of the electrons is
[Question ID = 14763]
1. 0.55 eV [Option ID = 29050]
2. 1 eV [Option ID = 29049]
3. 1.45 eV [Option ID = 29051]
4. 0.05 eV [Option ID = 29052]
Correct Answer :-
1 eV [Option ID = 29049]
An ideal photodiode is made of a material with a bandgap energy of 2.35 eV. It operates at 300 K
and is illuminated by monochromatic light with wavelength of 400 nm. Its maximum efficiency is
[Question ID = 14772]
1. 80% [Option ID = 29088]
2. 25% [Option ID = 29085]
3. 75.7% [Option ID = 29086]
4. 48% [Option ID = 29087]
Correct Answer :-
25% [Option ID = 29085]
If line A of X-ray beam gives a first order reflection maxima at a glancing angle of 30? to the
smooth face of a crystal and line B of ? = 0.92 ? gives a third order reflection maxima at an angle 60?
from the face of same crystal, then the wavelength of line A is
[Question ID = 14769]
1. 3.36 ? [Option ID = 29073]
2. 6.72 ? [Option ID = 29076]
3. 0.84 ? [Option ID = 29075]
4. 1.59 ? [Option ID = 29074]
Correct Answer :-
3.36 ? [Option ID = 29073]
If ? = Kein? then the value of ?K? after normalization in the limits 0 to is
[Question ID = 15449]
5)
6)
7)
1. [Option ID = 31794]
2. [Option ID = 31793]
3. [Option ID = 31795]
4. [Option ID = 31796]
Correct Answer :-
[Option ID = 31793]
In a microwave test bench, a dip is shown on the CRO display by rotating the micrometer of
wavemeter, which indicates
[Question ID = 14785]
1. frequency of microwave signal is not same as frequency of wavemeter [Option ID = 29139]
2. frequency of microwave signal is zero [Option ID = 29137]
3. frequency of microwave signal is same as frequency of wavemeter [Option ID = 29138]
4. no signal propagates [Option ID = 29140]
Correct Answer :-
frequency of microwave signal is zero [Option ID = 29137]
In a p-type Si sample the hole concentration is 8 ? 10
15
/ cm
3
. The intrinsic carrier concentration
is 4 ? 10
10
/ cm
3
. The electron concentration is
[Question ID = 14766]
1. zero [Option ID = 29061]
2. 4 ? 10
10
/cm
3
[Option ID = 29062]
3. 1.5 ? 10
25
/cm
3
[Option ID = 29063]
4. 2 ? 10
5
/cm
3
[Option ID = 29064]
Correct Answer :-
zero [Option ID = 29061]
Sigma Electronics sells a microwave receiver (A) having an operating spot noise figure of 10 dB
when driven by a source with effective noise temperature 130 K. Deltalink (B) sells a receiver with a
standard spot noise figure of 6 dB when driven by a source with effective noise temperature 190 K.
Zebrotronics (C) sells a receiver with standard spot noise figure of 6 dB when driven by a source with
effective noise temperature 290 K. The best receiver to purchase is
[Question ID = 14782]
1. (A) [Option ID = 29125]
2. None [Option ID = 29128]
3. (C ) [Option ID = 29126]
4. (B) [Option ID = 29127]
Correct Answer :-
8)
9)
10)
11)
(A) [Option ID = 29125]
A silicon bar of 1?m long and 100 ?m
2
in cross-sectional area is doped with 10
17
cm
-3
Phosphorus.
The saturation velocity is 10
7
cm/sec. The current at 300 K with 10V applied is
[Question ID = 14762]
1. 0.16 A [Option ID = 29047]
2. 0.8 A [Option ID = 29048]
3. 0.5 A [Option ID = 29046]
4. 1.2 A [Option ID = 29045]
Correct Answer :-
1.2 A [Option ID = 29045]
A silicon PN junction diode under reverse bias has depletion region of width 20 ?m. Given, the
relative permittivity of silicon, ?
r
= 12.7 and the permittivity of free space ?
0
= 8.85 ? 10
-12
F/m. The
depletion capacitance of the diode per square meter is
[Question ID = 14767]
1. 7.65 ?F [Option ID = 29065]
2. 3 ?F [Option ID = 29067]
3. 8.15 ?F [Option ID = 29066]
4. 5.62 ?F [Option ID = 29068]
Correct Answer :-
7.65 ?F [Option ID = 29065]
A silica optical fiber with a core diameter large enough to be considered by ray theory analysis
has a core refractive index of 1.65 and a cladding refractive index of 1.52. The numerical aperture
(NA) of the fiber is
[Question ID = 14774]
1. 0.32 [Option ID = 29094]
2. 0.56 [Option ID = 29096]
3. 0.42 [Option ID = 29095]
4. 0.64 [Option ID = 29093]
Correct Answer :-
0.64 [Option ID = 29093]
A step-index fiber has numerical aperture (NA) of 0.16 and its core index (n
1
) = 1.45. If core
diameter = 0.6 cm and ? = 0.9 nm then normalized frequency of the fiber is _____
[Question ID = 14776]
1. 6.70 ? 10
3
Hz [Option ID = 29103]
2. 1.67 ? 10
3
Hz [Option ID = 29101]
3. 3.35 ? 10
3
Hz [Option ID = 29102]
4. 1.83 ? 10
3
Hz [Option ID = 29104]
Correct Answer :-
1.67 ? 10
3
Hz [Option ID = 29101]
FirstRanker.com - FirstRanker's Choice
1)
2)
3)
4)
DU PhD in Electronics
Topic:- DU_J19_PHD_ELEC
An electron beam with 3 eV energy strikes a crystal of cadmium sulfide (CdS) (bandgap E
g
=2.45
eV). Electrons scattered by the crystal move at a velocity of 4.4 ? 10
5
m/s. The scattered energy (in
eV) of the electrons is
[Question ID = 14763]
1. 0.55 eV [Option ID = 29050]
2. 1 eV [Option ID = 29049]
3. 1.45 eV [Option ID = 29051]
4. 0.05 eV [Option ID = 29052]
Correct Answer :-
1 eV [Option ID = 29049]
An ideal photodiode is made of a material with a bandgap energy of 2.35 eV. It operates at 300 K
and is illuminated by monochromatic light with wavelength of 400 nm. Its maximum efficiency is
[Question ID = 14772]
1. 80% [Option ID = 29088]
2. 25% [Option ID = 29085]
3. 75.7% [Option ID = 29086]
4. 48% [Option ID = 29087]
Correct Answer :-
25% [Option ID = 29085]
If line A of X-ray beam gives a first order reflection maxima at a glancing angle of 30? to the
smooth face of a crystal and line B of ? = 0.92 ? gives a third order reflection maxima at an angle 60?
from the face of same crystal, then the wavelength of line A is
[Question ID = 14769]
1. 3.36 ? [Option ID = 29073]
2. 6.72 ? [Option ID = 29076]
3. 0.84 ? [Option ID = 29075]
4. 1.59 ? [Option ID = 29074]
Correct Answer :-
3.36 ? [Option ID = 29073]
If ? = Kein? then the value of ?K? after normalization in the limits 0 to is
[Question ID = 15449]
5)
6)
7)
1. [Option ID = 31794]
2. [Option ID = 31793]
3. [Option ID = 31795]
4. [Option ID = 31796]
Correct Answer :-
[Option ID = 31793]
In a microwave test bench, a dip is shown on the CRO display by rotating the micrometer of
wavemeter, which indicates
[Question ID = 14785]
1. frequency of microwave signal is not same as frequency of wavemeter [Option ID = 29139]
2. frequency of microwave signal is zero [Option ID = 29137]
3. frequency of microwave signal is same as frequency of wavemeter [Option ID = 29138]
4. no signal propagates [Option ID = 29140]
Correct Answer :-
frequency of microwave signal is zero [Option ID = 29137]
In a p-type Si sample the hole concentration is 8 ? 10
15
/ cm
3
. The intrinsic carrier concentration
is 4 ? 10
10
/ cm
3
. The electron concentration is
[Question ID = 14766]
1. zero [Option ID = 29061]
2. 4 ? 10
10
/cm
3
[Option ID = 29062]
3. 1.5 ? 10
25
/cm
3
[Option ID = 29063]
4. 2 ? 10
5
/cm
3
[Option ID = 29064]
Correct Answer :-
zero [Option ID = 29061]
Sigma Electronics sells a microwave receiver (A) having an operating spot noise figure of 10 dB
when driven by a source with effective noise temperature 130 K. Deltalink (B) sells a receiver with a
standard spot noise figure of 6 dB when driven by a source with effective noise temperature 190 K.
Zebrotronics (C) sells a receiver with standard spot noise figure of 6 dB when driven by a source with
effective noise temperature 290 K. The best receiver to purchase is
[Question ID = 14782]
1. (A) [Option ID = 29125]
2. None [Option ID = 29128]
3. (C ) [Option ID = 29126]
4. (B) [Option ID = 29127]
Correct Answer :-
8)
9)
10)
11)
(A) [Option ID = 29125]
A silicon bar of 1?m long and 100 ?m
2
in cross-sectional area is doped with 10
17
cm
-3
Phosphorus.
The saturation velocity is 10
7
cm/sec. The current at 300 K with 10V applied is
[Question ID = 14762]
1. 0.16 A [Option ID = 29047]
2. 0.8 A [Option ID = 29048]
3. 0.5 A [Option ID = 29046]
4. 1.2 A [Option ID = 29045]
Correct Answer :-
1.2 A [Option ID = 29045]
A silicon PN junction diode under reverse bias has depletion region of width 20 ?m. Given, the
relative permittivity of silicon, ?
r
= 12.7 and the permittivity of free space ?
0
= 8.85 ? 10
-12
F/m. The
depletion capacitance of the diode per square meter is
[Question ID = 14767]
1. 7.65 ?F [Option ID = 29065]
2. 3 ?F [Option ID = 29067]
3. 8.15 ?F [Option ID = 29066]
4. 5.62 ?F [Option ID = 29068]
Correct Answer :-
7.65 ?F [Option ID = 29065]
A silica optical fiber with a core diameter large enough to be considered by ray theory analysis
has a core refractive index of 1.65 and a cladding refractive index of 1.52. The numerical aperture
(NA) of the fiber is
[Question ID = 14774]
1. 0.32 [Option ID = 29094]
2. 0.56 [Option ID = 29096]
3. 0.42 [Option ID = 29095]
4. 0.64 [Option ID = 29093]
Correct Answer :-
0.64 [Option ID = 29093]
A step-index fiber has numerical aperture (NA) of 0.16 and its core index (n
1
) = 1.45. If core
diameter = 0.6 cm and ? = 0.9 nm then normalized frequency of the fiber is _____
[Question ID = 14776]
1. 6.70 ? 10
3
Hz [Option ID = 29103]
2. 1.67 ? 10
3
Hz [Option ID = 29101]
3. 3.35 ? 10
3
Hz [Option ID = 29102]
4. 1.83 ? 10
3
Hz [Option ID = 29104]
Correct Answer :-
1.67 ? 10
3
Hz [Option ID = 29101]
12)
13)
14)
15)
A three level laser emits laser light near the centre of visible band. If E
2
- E
1
= 2.36 eV then the
wavelength of radiation is
[Question ID = 14777]
1. 550 nm [Option ID = 29105]
2. 670 nm [Option ID = 29107]
3. 620 nm [Option ID = 29108]
4. 450 nm [Option ID = 29106]
Correct Answer :-
550 nm [Option ID = 29105]
log(1 + x ) = _______________
[Question ID = 14750]
1. [Option ID = 28997]
2. [Option ID = 29000]
3. [Option ID = 28999]
4. [Option ID = 28998]
Correct Answer :-
[Option ID = 28997]
If the bandgap of GaAsP is 1.98 eV then the color of emitted light is
[Question ID = 14770]
1. Blue [Option ID = 29077]
2. Green [Option ID = 29078]
3. Yellow [Option ID = 29080]
4. Red [Option ID = 29079]
Correct Answer :-
Blue [Option ID = 29077]
A laser beam emerging from a laser tube operating at 800 nm has a cross-sectional diameter of 2
mm. The diameter of the beam at a distance of 1 km is approximately
[Question ID = 14779]
1. 10 cm [Option ID = 29116]
2. 10 mm [Option ID = 29113]
3. 80 cm [Option ID = 29114]
4. 8 cm [Option ID = 29115]
Correct Answer :-
10 mm [Option ID = 29113]
FirstRanker.com - FirstRanker's Choice
1)
2)
3)
4)
DU PhD in Electronics
Topic:- DU_J19_PHD_ELEC
An electron beam with 3 eV energy strikes a crystal of cadmium sulfide (CdS) (bandgap E
g
=2.45
eV). Electrons scattered by the crystal move at a velocity of 4.4 ? 10
5
m/s. The scattered energy (in
eV) of the electrons is
[Question ID = 14763]
1. 0.55 eV [Option ID = 29050]
2. 1 eV [Option ID = 29049]
3. 1.45 eV [Option ID = 29051]
4. 0.05 eV [Option ID = 29052]
Correct Answer :-
1 eV [Option ID = 29049]
An ideal photodiode is made of a material with a bandgap energy of 2.35 eV. It operates at 300 K
and is illuminated by monochromatic light with wavelength of 400 nm. Its maximum efficiency is
[Question ID = 14772]
1. 80% [Option ID = 29088]
2. 25% [Option ID = 29085]
3. 75.7% [Option ID = 29086]
4. 48% [Option ID = 29087]
Correct Answer :-
25% [Option ID = 29085]
If line A of X-ray beam gives a first order reflection maxima at a glancing angle of 30? to the
smooth face of a crystal and line B of ? = 0.92 ? gives a third order reflection maxima at an angle 60?
from the face of same crystal, then the wavelength of line A is
[Question ID = 14769]
1. 3.36 ? [Option ID = 29073]
2. 6.72 ? [Option ID = 29076]
3. 0.84 ? [Option ID = 29075]
4. 1.59 ? [Option ID = 29074]
Correct Answer :-
3.36 ? [Option ID = 29073]
If ? = Kein? then the value of ?K? after normalization in the limits 0 to is
[Question ID = 15449]
5)
6)
7)
1. [Option ID = 31794]
2. [Option ID = 31793]
3. [Option ID = 31795]
4. [Option ID = 31796]
Correct Answer :-
[Option ID = 31793]
In a microwave test bench, a dip is shown on the CRO display by rotating the micrometer of
wavemeter, which indicates
[Question ID = 14785]
1. frequency of microwave signal is not same as frequency of wavemeter [Option ID = 29139]
2. frequency of microwave signal is zero [Option ID = 29137]
3. frequency of microwave signal is same as frequency of wavemeter [Option ID = 29138]
4. no signal propagates [Option ID = 29140]
Correct Answer :-
frequency of microwave signal is zero [Option ID = 29137]
In a p-type Si sample the hole concentration is 8 ? 10
15
/ cm
3
. The intrinsic carrier concentration
is 4 ? 10
10
/ cm
3
. The electron concentration is
[Question ID = 14766]
1. zero [Option ID = 29061]
2. 4 ? 10
10
/cm
3
[Option ID = 29062]
3. 1.5 ? 10
25
/cm
3
[Option ID = 29063]
4. 2 ? 10
5
/cm
3
[Option ID = 29064]
Correct Answer :-
zero [Option ID = 29061]
Sigma Electronics sells a microwave receiver (A) having an operating spot noise figure of 10 dB
when driven by a source with effective noise temperature 130 K. Deltalink (B) sells a receiver with a
standard spot noise figure of 6 dB when driven by a source with effective noise temperature 190 K.
Zebrotronics (C) sells a receiver with standard spot noise figure of 6 dB when driven by a source with
effective noise temperature 290 K. The best receiver to purchase is
[Question ID = 14782]
1. (A) [Option ID = 29125]
2. None [Option ID = 29128]
3. (C ) [Option ID = 29126]
4. (B) [Option ID = 29127]
Correct Answer :-
8)
9)
10)
11)
(A) [Option ID = 29125]
A silicon bar of 1?m long and 100 ?m
2
in cross-sectional area is doped with 10
17
cm
-3
Phosphorus.
The saturation velocity is 10
7
cm/sec. The current at 300 K with 10V applied is
[Question ID = 14762]
1. 0.16 A [Option ID = 29047]
2. 0.8 A [Option ID = 29048]
3. 0.5 A [Option ID = 29046]
4. 1.2 A [Option ID = 29045]
Correct Answer :-
1.2 A [Option ID = 29045]
A silicon PN junction diode under reverse bias has depletion region of width 20 ?m. Given, the
relative permittivity of silicon, ?
r
= 12.7 and the permittivity of free space ?
0
= 8.85 ? 10
-12
F/m. The
depletion capacitance of the diode per square meter is
[Question ID = 14767]
1. 7.65 ?F [Option ID = 29065]
2. 3 ?F [Option ID = 29067]
3. 8.15 ?F [Option ID = 29066]
4. 5.62 ?F [Option ID = 29068]
Correct Answer :-
7.65 ?F [Option ID = 29065]
A silica optical fiber with a core diameter large enough to be considered by ray theory analysis
has a core refractive index of 1.65 and a cladding refractive index of 1.52. The numerical aperture
(NA) of the fiber is
[Question ID = 14774]
1. 0.32 [Option ID = 29094]
2. 0.56 [Option ID = 29096]
3. 0.42 [Option ID = 29095]
4. 0.64 [Option ID = 29093]
Correct Answer :-
0.64 [Option ID = 29093]
A step-index fiber has numerical aperture (NA) of 0.16 and its core index (n
1
) = 1.45. If core
diameter = 0.6 cm and ? = 0.9 nm then normalized frequency of the fiber is _____
[Question ID = 14776]
1. 6.70 ? 10
3
Hz [Option ID = 29103]
2. 1.67 ? 10
3
Hz [Option ID = 29101]
3. 3.35 ? 10
3
Hz [Option ID = 29102]
4. 1.83 ? 10
3
Hz [Option ID = 29104]
Correct Answer :-
1.67 ? 10
3
Hz [Option ID = 29101]
12)
13)
14)
15)
A three level laser emits laser light near the centre of visible band. If E
2
- E
1
= 2.36 eV then the
wavelength of radiation is
[Question ID = 14777]
1. 550 nm [Option ID = 29105]
2. 670 nm [Option ID = 29107]
3. 620 nm [Option ID = 29108]
4. 450 nm [Option ID = 29106]
Correct Answer :-
550 nm [Option ID = 29105]
log(1 + x ) = _______________
[Question ID = 14750]
1. [Option ID = 28997]
2. [Option ID = 29000]
3. [Option ID = 28999]
4. [Option ID = 28998]
Correct Answer :-
[Option ID = 28997]
If the bandgap of GaAsP is 1.98 eV then the color of emitted light is
[Question ID = 14770]
1. Blue [Option ID = 29077]
2. Green [Option ID = 29078]
3. Yellow [Option ID = 29080]
4. Red [Option ID = 29079]
Correct Answer :-
Blue [Option ID = 29077]
A laser beam emerging from a laser tube operating at 800 nm has a cross-sectional diameter of 2
mm. The diameter of the beam at a distance of 1 km is approximately
[Question ID = 14779]
1. 10 cm [Option ID = 29116]
2. 10 mm [Option ID = 29113]
3. 80 cm [Option ID = 29114]
4. 8 cm [Option ID = 29115]
Correct Answer :-
10 mm [Option ID = 29113]
16)
17)
18)
19)
20)
A Si sample (n
i
= 1.5 ? 10
10
atoms/cm
3
) is doped with 10
17
As atoms/cm
3
. The position of E
f
related to E
i
is
[Question ID = 14761]
1. 0.895 eV [Option ID = 29043]
2. 0.407 eV [Option ID = 29044]
3. 0.532 eV [Option ID = 29042]
4. 0.217 eV [Option ID = 29041]
Correct Answer :-
0.217 eV [Option ID = 29041]
Attenuator reduces the microwave power in
[Question ID = 14783]
1. uni-direction [Option ID = 29130]
2. None of these [Option ID = 29132]
3. multi-direction [Option ID = 29131]
4. bi-direction [Option ID = 29129]
Correct Answer :-
bi-direction [Option ID = 29129]
A box contains 4 red balls and 6 black balls. Three balls are selected randomly from the box one
after another, without replacement. The probability that the selected set contains one red ball and
two black balls is
[Question ID = 14746]
1. 3/10 [Option ID = 28982]
2. 1/12 [Option ID = 28981]
3. 1/20 [Option ID = 28984]
4. 1/2 [Option ID = 28983]
Correct Answer :-
1/12 [Option ID = 28981]
Electron mobility in Si at room temperature (300 K) is 1400 cm
2
V
?1
s
?1
. The diffusion coefficient
of electrons is
[Question ID = 14765]
1. 36.22 cm
2
/s [Option ID = 29057]
2. 62.25 cm
2
/s [Option ID = 29059]
3. 32.76 cm
2
/s [Option ID = 29060]
4. 49.16 cm
2
/s [Option ID = 29058]
Correct Answer :-
36.22 cm
2
/s [Option ID = 29057]
In the Taylor series expansion of exp(x) + sin(x) about the point x = , the coefficient of (x -
)2 is
FirstRanker.com - FirstRanker's Choice
1)
2)
3)
4)
DU PhD in Electronics
Topic:- DU_J19_PHD_ELEC
An electron beam with 3 eV energy strikes a crystal of cadmium sulfide (CdS) (bandgap E
g
=2.45
eV). Electrons scattered by the crystal move at a velocity of 4.4 ? 10
5
m/s. The scattered energy (in
eV) of the electrons is
[Question ID = 14763]
1. 0.55 eV [Option ID = 29050]
2. 1 eV [Option ID = 29049]
3. 1.45 eV [Option ID = 29051]
4. 0.05 eV [Option ID = 29052]
Correct Answer :-
1 eV [Option ID = 29049]
An ideal photodiode is made of a material with a bandgap energy of 2.35 eV. It operates at 300 K
and is illuminated by monochromatic light with wavelength of 400 nm. Its maximum efficiency is
[Question ID = 14772]
1. 80% [Option ID = 29088]
2. 25% [Option ID = 29085]
3. 75.7% [Option ID = 29086]
4. 48% [Option ID = 29087]
Correct Answer :-
25% [Option ID = 29085]
If line A of X-ray beam gives a first order reflection maxima at a glancing angle of 30? to the
smooth face of a crystal and line B of ? = 0.92 ? gives a third order reflection maxima at an angle 60?
from the face of same crystal, then the wavelength of line A is
[Question ID = 14769]
1. 3.36 ? [Option ID = 29073]
2. 6.72 ? [Option ID = 29076]
3. 0.84 ? [Option ID = 29075]
4. 1.59 ? [Option ID = 29074]
Correct Answer :-
3.36 ? [Option ID = 29073]
If ? = Kein? then the value of ?K? after normalization in the limits 0 to is
[Question ID = 15449]
5)
6)
7)
1. [Option ID = 31794]
2. [Option ID = 31793]
3. [Option ID = 31795]
4. [Option ID = 31796]
Correct Answer :-
[Option ID = 31793]
In a microwave test bench, a dip is shown on the CRO display by rotating the micrometer of
wavemeter, which indicates
[Question ID = 14785]
1. frequency of microwave signal is not same as frequency of wavemeter [Option ID = 29139]
2. frequency of microwave signal is zero [Option ID = 29137]
3. frequency of microwave signal is same as frequency of wavemeter [Option ID = 29138]
4. no signal propagates [Option ID = 29140]
Correct Answer :-
frequency of microwave signal is zero [Option ID = 29137]
In a p-type Si sample the hole concentration is 8 ? 10
15
/ cm
3
. The intrinsic carrier concentration
is 4 ? 10
10
/ cm
3
. The electron concentration is
[Question ID = 14766]
1. zero [Option ID = 29061]
2. 4 ? 10
10
/cm
3
[Option ID = 29062]
3. 1.5 ? 10
25
/cm
3
[Option ID = 29063]
4. 2 ? 10
5
/cm
3
[Option ID = 29064]
Correct Answer :-
zero [Option ID = 29061]
Sigma Electronics sells a microwave receiver (A) having an operating spot noise figure of 10 dB
when driven by a source with effective noise temperature 130 K. Deltalink (B) sells a receiver with a
standard spot noise figure of 6 dB when driven by a source with effective noise temperature 190 K.
Zebrotronics (C) sells a receiver with standard spot noise figure of 6 dB when driven by a source with
effective noise temperature 290 K. The best receiver to purchase is
[Question ID = 14782]
1. (A) [Option ID = 29125]
2. None [Option ID = 29128]
3. (C ) [Option ID = 29126]
4. (B) [Option ID = 29127]
Correct Answer :-
8)
9)
10)
11)
(A) [Option ID = 29125]
A silicon bar of 1?m long and 100 ?m
2
in cross-sectional area is doped with 10
17
cm
-3
Phosphorus.
The saturation velocity is 10
7
cm/sec. The current at 300 K with 10V applied is
[Question ID = 14762]
1. 0.16 A [Option ID = 29047]
2. 0.8 A [Option ID = 29048]
3. 0.5 A [Option ID = 29046]
4. 1.2 A [Option ID = 29045]
Correct Answer :-
1.2 A [Option ID = 29045]
A silicon PN junction diode under reverse bias has depletion region of width 20 ?m. Given, the
relative permittivity of silicon, ?
r
= 12.7 and the permittivity of free space ?
0
= 8.85 ? 10
-12
F/m. The
depletion capacitance of the diode per square meter is
[Question ID = 14767]
1. 7.65 ?F [Option ID = 29065]
2. 3 ?F [Option ID = 29067]
3. 8.15 ?F [Option ID = 29066]
4. 5.62 ?F [Option ID = 29068]
Correct Answer :-
7.65 ?F [Option ID = 29065]
A silica optical fiber with a core diameter large enough to be considered by ray theory analysis
has a core refractive index of 1.65 and a cladding refractive index of 1.52. The numerical aperture
(NA) of the fiber is
[Question ID = 14774]
1. 0.32 [Option ID = 29094]
2. 0.56 [Option ID = 29096]
3. 0.42 [Option ID = 29095]
4. 0.64 [Option ID = 29093]
Correct Answer :-
0.64 [Option ID = 29093]
A step-index fiber has numerical aperture (NA) of 0.16 and its core index (n
1
) = 1.45. If core
diameter = 0.6 cm and ? = 0.9 nm then normalized frequency of the fiber is _____
[Question ID = 14776]
1. 6.70 ? 10
3
Hz [Option ID = 29103]
2. 1.67 ? 10
3
Hz [Option ID = 29101]
3. 3.35 ? 10
3
Hz [Option ID = 29102]
4. 1.83 ? 10
3
Hz [Option ID = 29104]
Correct Answer :-
1.67 ? 10
3
Hz [Option ID = 29101]
12)
13)
14)
15)
A three level laser emits laser light near the centre of visible band. If E
2
- E
1
= 2.36 eV then the
wavelength of radiation is
[Question ID = 14777]
1. 550 nm [Option ID = 29105]
2. 670 nm [Option ID = 29107]
3. 620 nm [Option ID = 29108]
4. 450 nm [Option ID = 29106]
Correct Answer :-
550 nm [Option ID = 29105]
log(1 + x ) = _______________
[Question ID = 14750]
1. [Option ID = 28997]
2. [Option ID = 29000]
3. [Option ID = 28999]
4. [Option ID = 28998]
Correct Answer :-
[Option ID = 28997]
If the bandgap of GaAsP is 1.98 eV then the color of emitted light is
[Question ID = 14770]
1. Blue [Option ID = 29077]
2. Green [Option ID = 29078]
3. Yellow [Option ID = 29080]
4. Red [Option ID = 29079]
Correct Answer :-
Blue [Option ID = 29077]
A laser beam emerging from a laser tube operating at 800 nm has a cross-sectional diameter of 2
mm. The diameter of the beam at a distance of 1 km is approximately
[Question ID = 14779]
1. 10 cm [Option ID = 29116]
2. 10 mm [Option ID = 29113]
3. 80 cm [Option ID = 29114]
4. 8 cm [Option ID = 29115]
Correct Answer :-
10 mm [Option ID = 29113]
16)
17)
18)
19)
20)
A Si sample (n
i
= 1.5 ? 10
10
atoms/cm
3
) is doped with 10
17
As atoms/cm
3
. The position of E
f
related to E
i
is
[Question ID = 14761]
1. 0.895 eV [Option ID = 29043]
2. 0.407 eV [Option ID = 29044]
3. 0.532 eV [Option ID = 29042]
4. 0.217 eV [Option ID = 29041]
Correct Answer :-
0.217 eV [Option ID = 29041]
Attenuator reduces the microwave power in
[Question ID = 14783]
1. uni-direction [Option ID = 29130]
2. None of these [Option ID = 29132]
3. multi-direction [Option ID = 29131]
4. bi-direction [Option ID = 29129]
Correct Answer :-
bi-direction [Option ID = 29129]
A box contains 4 red balls and 6 black balls. Three balls are selected randomly from the box one
after another, without replacement. The probability that the selected set contains one red ball and
two black balls is
[Question ID = 14746]
1. 3/10 [Option ID = 28982]
2. 1/12 [Option ID = 28981]
3. 1/20 [Option ID = 28984]
4. 1/2 [Option ID = 28983]
Correct Answer :-
1/12 [Option ID = 28981]
Electron mobility in Si at room temperature (300 K) is 1400 cm
2
V
?1
s
?1
. The diffusion coefficient
of electrons is
[Question ID = 14765]
1. 36.22 cm
2
/s [Option ID = 29057]
2. 62.25 cm
2
/s [Option ID = 29059]
3. 32.76 cm
2
/s [Option ID = 29060]
4. 49.16 cm
2
/s [Option ID = 29058]
Correct Answer :-
36.22 cm
2
/s [Option ID = 29057]
In the Taylor series expansion of exp(x) + sin(x) about the point x = , the coefficient of (x -
)2 is
21)
22)
23)
24)
[Question ID = 15451]
1. 0.5 exp( ) [Option ID = 31802]
2. exp( ) [Option ID = 31801]
3. exp( ) - 1 [Option ID = 31804]
4. exp( ) + 1 [Option ID = 31803]
Correct Answer :-
exp( ) [Option ID = 31801]
In the expression 6 + 8i = 10e
i?
, the value of ? is,
[Question ID = 14743]
1. 85.16? [Option ID = 28971]
2. 53.13? [Option ID = 28972]
3. 36.16? [Option ID = 28970]
4. 13.13? [Option ID = 28969]
Correct Answer :-
13.13? [Option ID = 28969]
In the interval [0, ] the equation x = cos x
[Question ID = 15450]
1. exactly one solution [Option ID = 31799]
2. exactly two solutions [Option ID = 31797]
3. no solutions [Option ID = 31798]
4. an infinite number of solutions [Option ID = 31800]
Correct Answer :-
exactly two solutions [Option ID = 31797]
Choose the correct match out of the following options given below
Column I Column II
P. 2
nd
order DEs 1. Newton ? Raphson method
Q. Non-linear algebraic equations 2. Gauss Elimination
R. Linear algebraic equations 3. Simpson?s rule
S. Numerical integration 4. Runge-kutta method
[Question ID = 14754]
1. P->4 Q->1 R->2 S->3 [Option ID = 29014]
2. P->4 Q->2 R->3 S->1 [Option ID = 29015]
3. P->4 Q->2 R->1 S->3 [Option ID = 29016]
4. P->1 Q->2 R->3 S->4 [Option ID = 29013]
Correct Answer :-
P->1 Q->2 R->3 S->4 [Option ID = 29013]
Helical antenna has the following polarization
[Question ID = 14788]
FirstRanker.com - FirstRanker's Choice
1)
2)
3)
4)
DU PhD in Electronics
Topic:- DU_J19_PHD_ELEC
An electron beam with 3 eV energy strikes a crystal of cadmium sulfide (CdS) (bandgap E
g
=2.45
eV). Electrons scattered by the crystal move at a velocity of 4.4 ? 10
5
m/s. The scattered energy (in
eV) of the electrons is
[Question ID = 14763]
1. 0.55 eV [Option ID = 29050]
2. 1 eV [Option ID = 29049]
3. 1.45 eV [Option ID = 29051]
4. 0.05 eV [Option ID = 29052]
Correct Answer :-
1 eV [Option ID = 29049]
An ideal photodiode is made of a material with a bandgap energy of 2.35 eV. It operates at 300 K
and is illuminated by monochromatic light with wavelength of 400 nm. Its maximum efficiency is
[Question ID = 14772]
1. 80% [Option ID = 29088]
2. 25% [Option ID = 29085]
3. 75.7% [Option ID = 29086]
4. 48% [Option ID = 29087]
Correct Answer :-
25% [Option ID = 29085]
If line A of X-ray beam gives a first order reflection maxima at a glancing angle of 30? to the
smooth face of a crystal and line B of ? = 0.92 ? gives a third order reflection maxima at an angle 60?
from the face of same crystal, then the wavelength of line A is
[Question ID = 14769]
1. 3.36 ? [Option ID = 29073]
2. 6.72 ? [Option ID = 29076]
3. 0.84 ? [Option ID = 29075]
4. 1.59 ? [Option ID = 29074]
Correct Answer :-
3.36 ? [Option ID = 29073]
If ? = Kein? then the value of ?K? after normalization in the limits 0 to is
[Question ID = 15449]
5)
6)
7)
1. [Option ID = 31794]
2. [Option ID = 31793]
3. [Option ID = 31795]
4. [Option ID = 31796]
Correct Answer :-
[Option ID = 31793]
In a microwave test bench, a dip is shown on the CRO display by rotating the micrometer of
wavemeter, which indicates
[Question ID = 14785]
1. frequency of microwave signal is not same as frequency of wavemeter [Option ID = 29139]
2. frequency of microwave signal is zero [Option ID = 29137]
3. frequency of microwave signal is same as frequency of wavemeter [Option ID = 29138]
4. no signal propagates [Option ID = 29140]
Correct Answer :-
frequency of microwave signal is zero [Option ID = 29137]
In a p-type Si sample the hole concentration is 8 ? 10
15
/ cm
3
. The intrinsic carrier concentration
is 4 ? 10
10
/ cm
3
. The electron concentration is
[Question ID = 14766]
1. zero [Option ID = 29061]
2. 4 ? 10
10
/cm
3
[Option ID = 29062]
3. 1.5 ? 10
25
/cm
3
[Option ID = 29063]
4. 2 ? 10
5
/cm
3
[Option ID = 29064]
Correct Answer :-
zero [Option ID = 29061]
Sigma Electronics sells a microwave receiver (A) having an operating spot noise figure of 10 dB
when driven by a source with effective noise temperature 130 K. Deltalink (B) sells a receiver with a
standard spot noise figure of 6 dB when driven by a source with effective noise temperature 190 K.
Zebrotronics (C) sells a receiver with standard spot noise figure of 6 dB when driven by a source with
effective noise temperature 290 K. The best receiver to purchase is
[Question ID = 14782]
1. (A) [Option ID = 29125]
2. None [Option ID = 29128]
3. (C ) [Option ID = 29126]
4. (B) [Option ID = 29127]
Correct Answer :-
8)
9)
10)
11)
(A) [Option ID = 29125]
A silicon bar of 1?m long and 100 ?m
2
in cross-sectional area is doped with 10
17
cm
-3
Phosphorus.
The saturation velocity is 10
7
cm/sec. The current at 300 K with 10V applied is
[Question ID = 14762]
1. 0.16 A [Option ID = 29047]
2. 0.8 A [Option ID = 29048]
3. 0.5 A [Option ID = 29046]
4. 1.2 A [Option ID = 29045]
Correct Answer :-
1.2 A [Option ID = 29045]
A silicon PN junction diode under reverse bias has depletion region of width 20 ?m. Given, the
relative permittivity of silicon, ?
r
= 12.7 and the permittivity of free space ?
0
= 8.85 ? 10
-12
F/m. The
depletion capacitance of the diode per square meter is
[Question ID = 14767]
1. 7.65 ?F [Option ID = 29065]
2. 3 ?F [Option ID = 29067]
3. 8.15 ?F [Option ID = 29066]
4. 5.62 ?F [Option ID = 29068]
Correct Answer :-
7.65 ?F [Option ID = 29065]
A silica optical fiber with a core diameter large enough to be considered by ray theory analysis
has a core refractive index of 1.65 and a cladding refractive index of 1.52. The numerical aperture
(NA) of the fiber is
[Question ID = 14774]
1. 0.32 [Option ID = 29094]
2. 0.56 [Option ID = 29096]
3. 0.42 [Option ID = 29095]
4. 0.64 [Option ID = 29093]
Correct Answer :-
0.64 [Option ID = 29093]
A step-index fiber has numerical aperture (NA) of 0.16 and its core index (n
1
) = 1.45. If core
diameter = 0.6 cm and ? = 0.9 nm then normalized frequency of the fiber is _____
[Question ID = 14776]
1. 6.70 ? 10
3
Hz [Option ID = 29103]
2. 1.67 ? 10
3
Hz [Option ID = 29101]
3. 3.35 ? 10
3
Hz [Option ID = 29102]
4. 1.83 ? 10
3
Hz [Option ID = 29104]
Correct Answer :-
1.67 ? 10
3
Hz [Option ID = 29101]
12)
13)
14)
15)
A three level laser emits laser light near the centre of visible band. If E
2
- E
1
= 2.36 eV then the
wavelength of radiation is
[Question ID = 14777]
1. 550 nm [Option ID = 29105]
2. 670 nm [Option ID = 29107]
3. 620 nm [Option ID = 29108]
4. 450 nm [Option ID = 29106]
Correct Answer :-
550 nm [Option ID = 29105]
log(1 + x ) = _______________
[Question ID = 14750]
1. [Option ID = 28997]
2. [Option ID = 29000]
3. [Option ID = 28999]
4. [Option ID = 28998]
Correct Answer :-
[Option ID = 28997]
If the bandgap of GaAsP is 1.98 eV then the color of emitted light is
[Question ID = 14770]
1. Blue [Option ID = 29077]
2. Green [Option ID = 29078]
3. Yellow [Option ID = 29080]
4. Red [Option ID = 29079]
Correct Answer :-
Blue [Option ID = 29077]
A laser beam emerging from a laser tube operating at 800 nm has a cross-sectional diameter of 2
mm. The diameter of the beam at a distance of 1 km is approximately
[Question ID = 14779]
1. 10 cm [Option ID = 29116]
2. 10 mm [Option ID = 29113]
3. 80 cm [Option ID = 29114]
4. 8 cm [Option ID = 29115]
Correct Answer :-
10 mm [Option ID = 29113]
16)
17)
18)
19)
20)
A Si sample (n
i
= 1.5 ? 10
10
atoms/cm
3
) is doped with 10
17
As atoms/cm
3
. The position of E
f
related to E
i
is
[Question ID = 14761]
1. 0.895 eV [Option ID = 29043]
2. 0.407 eV [Option ID = 29044]
3. 0.532 eV [Option ID = 29042]
4. 0.217 eV [Option ID = 29041]
Correct Answer :-
0.217 eV [Option ID = 29041]
Attenuator reduces the microwave power in
[Question ID = 14783]
1. uni-direction [Option ID = 29130]
2. None of these [Option ID = 29132]
3. multi-direction [Option ID = 29131]
4. bi-direction [Option ID = 29129]
Correct Answer :-
bi-direction [Option ID = 29129]
A box contains 4 red balls and 6 black balls. Three balls are selected randomly from the box one
after another, without replacement. The probability that the selected set contains one red ball and
two black balls is
[Question ID = 14746]
1. 3/10 [Option ID = 28982]
2. 1/12 [Option ID = 28981]
3. 1/20 [Option ID = 28984]
4. 1/2 [Option ID = 28983]
Correct Answer :-
1/12 [Option ID = 28981]
Electron mobility in Si at room temperature (300 K) is 1400 cm
2
V
?1
s
?1
. The diffusion coefficient
of electrons is
[Question ID = 14765]
1. 36.22 cm
2
/s [Option ID = 29057]
2. 62.25 cm
2
/s [Option ID = 29059]
3. 32.76 cm
2
/s [Option ID = 29060]
4. 49.16 cm
2
/s [Option ID = 29058]
Correct Answer :-
36.22 cm
2
/s [Option ID = 29057]
In the Taylor series expansion of exp(x) + sin(x) about the point x = , the coefficient of (x -
)2 is
21)
22)
23)
24)
[Question ID = 15451]
1. 0.5 exp( ) [Option ID = 31802]
2. exp( ) [Option ID = 31801]
3. exp( ) - 1 [Option ID = 31804]
4. exp( ) + 1 [Option ID = 31803]
Correct Answer :-
exp( ) [Option ID = 31801]
In the expression 6 + 8i = 10e
i?
, the value of ? is,
[Question ID = 14743]
1. 85.16? [Option ID = 28971]
2. 53.13? [Option ID = 28972]
3. 36.16? [Option ID = 28970]
4. 13.13? [Option ID = 28969]
Correct Answer :-
13.13? [Option ID = 28969]
In the interval [0, ] the equation x = cos x
[Question ID = 15450]
1. exactly one solution [Option ID = 31799]
2. exactly two solutions [Option ID = 31797]
3. no solutions [Option ID = 31798]
4. an infinite number of solutions [Option ID = 31800]
Correct Answer :-
exactly two solutions [Option ID = 31797]
Choose the correct match out of the following options given below
Column I Column II
P. 2
nd
order DEs 1. Newton ? Raphson method
Q. Non-linear algebraic equations 2. Gauss Elimination
R. Linear algebraic equations 3. Simpson?s rule
S. Numerical integration 4. Runge-kutta method
[Question ID = 14754]
1. P->4 Q->1 R->2 S->3 [Option ID = 29014]
2. P->4 Q->2 R->3 S->1 [Option ID = 29015]
3. P->4 Q->2 R->1 S->3 [Option ID = 29016]
4. P->1 Q->2 R->3 S->4 [Option ID = 29013]
Correct Answer :-
P->1 Q->2 R->3 S->4 [Option ID = 29013]
Helical antenna has the following polarization
[Question ID = 14788]
25)
26)
27)
1. vertical [Option ID = 29152]
2. linear [Option ID = 29149]
3. elliptical [Option ID = 29151]
4. circular [Option ID = 29150]
Correct Answer :-
linear [Option ID = 29149]
Match the typical spectroscopic regions specified in Part-I with corresponding type of transitions
in Part-II and choose the correct answer from the following options.
Part-I Part-II
K. Infrared region 1. Electron transition involving valance electrons
L. Ultraviolet visible region 2. Nuclear transitions
M. X-ray region 3. Vibrational transitions of molecules
N. ?-ray region 4. Transitions involving inner shell electrons
[Question ID = 14775]
1. K->4 L->2 M->1 N->3 [Option ID = 29098]
2. K->3 L->4 M->1 N->2 [Option ID = 29100]
3. K->3 L->1 M->4 N->2 [Option ID = 29097]
4. K->1 L->2 M->3 N->4 [Option ID = 29099]
Correct Answer :-
K->3 L->1 M->4 N->2 [Option ID = 29097]
[Question ID = 14757]
1. [Option ID = 29027]
2. [Option ID = 29026]
3. [Option ID = 29025]
4. [Option ID = 29028]
Correct Answer :-
[Option ID = 29025]
[Question ID = 14755]
1. 3/5 [Option ID = 29018]
2. -5/2 [Option ID = 29017]
FirstRanker.com - FirstRanker's Choice
1)
2)
3)
4)
DU PhD in Electronics
Topic:- DU_J19_PHD_ELEC
An electron beam with 3 eV energy strikes a crystal of cadmium sulfide (CdS) (bandgap E
g
=2.45
eV). Electrons scattered by the crystal move at a velocity of 4.4 ? 10
5
m/s. The scattered energy (in
eV) of the electrons is
[Question ID = 14763]
1. 0.55 eV [Option ID = 29050]
2. 1 eV [Option ID = 29049]
3. 1.45 eV [Option ID = 29051]
4. 0.05 eV [Option ID = 29052]
Correct Answer :-
1 eV [Option ID = 29049]
An ideal photodiode is made of a material with a bandgap energy of 2.35 eV. It operates at 300 K
and is illuminated by monochromatic light with wavelength of 400 nm. Its maximum efficiency is
[Question ID = 14772]
1. 80% [Option ID = 29088]
2. 25% [Option ID = 29085]
3. 75.7% [Option ID = 29086]
4. 48% [Option ID = 29087]
Correct Answer :-
25% [Option ID = 29085]
If line A of X-ray beam gives a first order reflection maxima at a glancing angle of 30? to the
smooth face of a crystal and line B of ? = 0.92 ? gives a third order reflection maxima at an angle 60?
from the face of same crystal, then the wavelength of line A is
[Question ID = 14769]
1. 3.36 ? [Option ID = 29073]
2. 6.72 ? [Option ID = 29076]
3. 0.84 ? [Option ID = 29075]
4. 1.59 ? [Option ID = 29074]
Correct Answer :-
3.36 ? [Option ID = 29073]
If ? = Kein? then the value of ?K? after normalization in the limits 0 to is
[Question ID = 15449]
5)
6)
7)
1. [Option ID = 31794]
2. [Option ID = 31793]
3. [Option ID = 31795]
4. [Option ID = 31796]
Correct Answer :-
[Option ID = 31793]
In a microwave test bench, a dip is shown on the CRO display by rotating the micrometer of
wavemeter, which indicates
[Question ID = 14785]
1. frequency of microwave signal is not same as frequency of wavemeter [Option ID = 29139]
2. frequency of microwave signal is zero [Option ID = 29137]
3. frequency of microwave signal is same as frequency of wavemeter [Option ID = 29138]
4. no signal propagates [Option ID = 29140]
Correct Answer :-
frequency of microwave signal is zero [Option ID = 29137]
In a p-type Si sample the hole concentration is 8 ? 10
15
/ cm
3
. The intrinsic carrier concentration
is 4 ? 10
10
/ cm
3
. The electron concentration is
[Question ID = 14766]
1. zero [Option ID = 29061]
2. 4 ? 10
10
/cm
3
[Option ID = 29062]
3. 1.5 ? 10
25
/cm
3
[Option ID = 29063]
4. 2 ? 10
5
/cm
3
[Option ID = 29064]
Correct Answer :-
zero [Option ID = 29061]
Sigma Electronics sells a microwave receiver (A) having an operating spot noise figure of 10 dB
when driven by a source with effective noise temperature 130 K. Deltalink (B) sells a receiver with a
standard spot noise figure of 6 dB when driven by a source with effective noise temperature 190 K.
Zebrotronics (C) sells a receiver with standard spot noise figure of 6 dB when driven by a source with
effective noise temperature 290 K. The best receiver to purchase is
[Question ID = 14782]
1. (A) [Option ID = 29125]
2. None [Option ID = 29128]
3. (C ) [Option ID = 29126]
4. (B) [Option ID = 29127]
Correct Answer :-
8)
9)
10)
11)
(A) [Option ID = 29125]
A silicon bar of 1?m long and 100 ?m
2
in cross-sectional area is doped with 10
17
cm
-3
Phosphorus.
The saturation velocity is 10
7
cm/sec. The current at 300 K with 10V applied is
[Question ID = 14762]
1. 0.16 A [Option ID = 29047]
2. 0.8 A [Option ID = 29048]
3. 0.5 A [Option ID = 29046]
4. 1.2 A [Option ID = 29045]
Correct Answer :-
1.2 A [Option ID = 29045]
A silicon PN junction diode under reverse bias has depletion region of width 20 ?m. Given, the
relative permittivity of silicon, ?
r
= 12.7 and the permittivity of free space ?
0
= 8.85 ? 10
-12
F/m. The
depletion capacitance of the diode per square meter is
[Question ID = 14767]
1. 7.65 ?F [Option ID = 29065]
2. 3 ?F [Option ID = 29067]
3. 8.15 ?F [Option ID = 29066]
4. 5.62 ?F [Option ID = 29068]
Correct Answer :-
7.65 ?F [Option ID = 29065]
A silica optical fiber with a core diameter large enough to be considered by ray theory analysis
has a core refractive index of 1.65 and a cladding refractive index of 1.52. The numerical aperture
(NA) of the fiber is
[Question ID = 14774]
1. 0.32 [Option ID = 29094]
2. 0.56 [Option ID = 29096]
3. 0.42 [Option ID = 29095]
4. 0.64 [Option ID = 29093]
Correct Answer :-
0.64 [Option ID = 29093]
A step-index fiber has numerical aperture (NA) of 0.16 and its core index (n
1
) = 1.45. If core
diameter = 0.6 cm and ? = 0.9 nm then normalized frequency of the fiber is _____
[Question ID = 14776]
1. 6.70 ? 10
3
Hz [Option ID = 29103]
2. 1.67 ? 10
3
Hz [Option ID = 29101]
3. 3.35 ? 10
3
Hz [Option ID = 29102]
4. 1.83 ? 10
3
Hz [Option ID = 29104]
Correct Answer :-
1.67 ? 10
3
Hz [Option ID = 29101]
12)
13)
14)
15)
A three level laser emits laser light near the centre of visible band. If E
2
- E
1
= 2.36 eV then the
wavelength of radiation is
[Question ID = 14777]
1. 550 nm [Option ID = 29105]
2. 670 nm [Option ID = 29107]
3. 620 nm [Option ID = 29108]
4. 450 nm [Option ID = 29106]
Correct Answer :-
550 nm [Option ID = 29105]
log(1 + x ) = _______________
[Question ID = 14750]
1. [Option ID = 28997]
2. [Option ID = 29000]
3. [Option ID = 28999]
4. [Option ID = 28998]
Correct Answer :-
[Option ID = 28997]
If the bandgap of GaAsP is 1.98 eV then the color of emitted light is
[Question ID = 14770]
1. Blue [Option ID = 29077]
2. Green [Option ID = 29078]
3. Yellow [Option ID = 29080]
4. Red [Option ID = 29079]
Correct Answer :-
Blue [Option ID = 29077]
A laser beam emerging from a laser tube operating at 800 nm has a cross-sectional diameter of 2
mm. The diameter of the beam at a distance of 1 km is approximately
[Question ID = 14779]
1. 10 cm [Option ID = 29116]
2. 10 mm [Option ID = 29113]
3. 80 cm [Option ID = 29114]
4. 8 cm [Option ID = 29115]
Correct Answer :-
10 mm [Option ID = 29113]
16)
17)
18)
19)
20)
A Si sample (n
i
= 1.5 ? 10
10
atoms/cm
3
) is doped with 10
17
As atoms/cm
3
. The position of E
f
related to E
i
is
[Question ID = 14761]
1. 0.895 eV [Option ID = 29043]
2. 0.407 eV [Option ID = 29044]
3. 0.532 eV [Option ID = 29042]
4. 0.217 eV [Option ID = 29041]
Correct Answer :-
0.217 eV [Option ID = 29041]
Attenuator reduces the microwave power in
[Question ID = 14783]
1. uni-direction [Option ID = 29130]
2. None of these [Option ID = 29132]
3. multi-direction [Option ID = 29131]
4. bi-direction [Option ID = 29129]
Correct Answer :-
bi-direction [Option ID = 29129]
A box contains 4 red balls and 6 black balls. Three balls are selected randomly from the box one
after another, without replacement. The probability that the selected set contains one red ball and
two black balls is
[Question ID = 14746]
1. 3/10 [Option ID = 28982]
2. 1/12 [Option ID = 28981]
3. 1/20 [Option ID = 28984]
4. 1/2 [Option ID = 28983]
Correct Answer :-
1/12 [Option ID = 28981]
Electron mobility in Si at room temperature (300 K) is 1400 cm
2
V
?1
s
?1
. The diffusion coefficient
of electrons is
[Question ID = 14765]
1. 36.22 cm
2
/s [Option ID = 29057]
2. 62.25 cm
2
/s [Option ID = 29059]
3. 32.76 cm
2
/s [Option ID = 29060]
4. 49.16 cm
2
/s [Option ID = 29058]
Correct Answer :-
36.22 cm
2
/s [Option ID = 29057]
In the Taylor series expansion of exp(x) + sin(x) about the point x = , the coefficient of (x -
)2 is
21)
22)
23)
24)
[Question ID = 15451]
1. 0.5 exp( ) [Option ID = 31802]
2. exp( ) [Option ID = 31801]
3. exp( ) - 1 [Option ID = 31804]
4. exp( ) + 1 [Option ID = 31803]
Correct Answer :-
exp( ) [Option ID = 31801]
In the expression 6 + 8i = 10e
i?
, the value of ? is,
[Question ID = 14743]
1. 85.16? [Option ID = 28971]
2. 53.13? [Option ID = 28972]
3. 36.16? [Option ID = 28970]
4. 13.13? [Option ID = 28969]
Correct Answer :-
13.13? [Option ID = 28969]
In the interval [0, ] the equation x = cos x
[Question ID = 15450]
1. exactly one solution [Option ID = 31799]
2. exactly two solutions [Option ID = 31797]
3. no solutions [Option ID = 31798]
4. an infinite number of solutions [Option ID = 31800]
Correct Answer :-
exactly two solutions [Option ID = 31797]
Choose the correct match out of the following options given below
Column I Column II
P. 2
nd
order DEs 1. Newton ? Raphson method
Q. Non-linear algebraic equations 2. Gauss Elimination
R. Linear algebraic equations 3. Simpson?s rule
S. Numerical integration 4. Runge-kutta method
[Question ID = 14754]
1. P->4 Q->1 R->2 S->3 [Option ID = 29014]
2. P->4 Q->2 R->3 S->1 [Option ID = 29015]
3. P->4 Q->2 R->1 S->3 [Option ID = 29016]
4. P->1 Q->2 R->3 S->4 [Option ID = 29013]
Correct Answer :-
P->1 Q->2 R->3 S->4 [Option ID = 29013]
Helical antenna has the following polarization
[Question ID = 14788]
25)
26)
27)
1. vertical [Option ID = 29152]
2. linear [Option ID = 29149]
3. elliptical [Option ID = 29151]
4. circular [Option ID = 29150]
Correct Answer :-
linear [Option ID = 29149]
Match the typical spectroscopic regions specified in Part-I with corresponding type of transitions
in Part-II and choose the correct answer from the following options.
Part-I Part-II
K. Infrared region 1. Electron transition involving valance electrons
L. Ultraviolet visible region 2. Nuclear transitions
M. X-ray region 3. Vibrational transitions of molecules
N. ?-ray region 4. Transitions involving inner shell electrons
[Question ID = 14775]
1. K->4 L->2 M->1 N->3 [Option ID = 29098]
2. K->3 L->4 M->1 N->2 [Option ID = 29100]
3. K->3 L->1 M->4 N->2 [Option ID = 29097]
4. K->1 L->2 M->3 N->4 [Option ID = 29099]
Correct Answer :-
K->3 L->1 M->4 N->2 [Option ID = 29097]
[Question ID = 14757]
1. [Option ID = 29027]
2. [Option ID = 29026]
3. [Option ID = 29025]
4. [Option ID = 29028]
Correct Answer :-
[Option ID = 29025]
[Question ID = 14755]
1. 3/5 [Option ID = 29018]
2. -5/2 [Option ID = 29017]
28)
29)
30)
31)
3. -5/3 [Option ID = 29020]
4. -2/5 [Option ID = 29019]
Correct Answer :-
-5/2 [Option ID = 29017]
[Question ID = 14756]
1. 1,0,2,3 [Option ID = 29021]
2. -1,1,0,3 [Option ID = 29024]
3. -1,1,0,2 [Option ID = 29023]
4. -2, -1, 1, 2 [Option ID = 29022]
Correct Answer :-
1,0,2,3 [Option ID = 29021]
[Question ID = 14747]
1. 20/3 [Option ID = 28987]
2. 40/3 [Option ID = 28986]
3. 0 [Option ID = 28988]
4. 4/3 [Option ID = 28985]
Correct Answer :-
4/3 [Option ID = 28985]
[Question ID = 14760]
1. 0.306 [Option ID = 29038]
2. 2.432 [Option ID = 29039]
3. 1.694 [Option ID = 29040]
4. 0.732 [Option ID = 29037]
Correct Answer :-
0.732 [Option ID = 29037]
FirstRanker.com - FirstRanker's Choice
1)
2)
3)
4)
DU PhD in Electronics
Topic:- DU_J19_PHD_ELEC
An electron beam with 3 eV energy strikes a crystal of cadmium sulfide (CdS) (bandgap E
g
=2.45
eV). Electrons scattered by the crystal move at a velocity of 4.4 ? 10
5
m/s. The scattered energy (in
eV) of the electrons is
[Question ID = 14763]
1. 0.55 eV [Option ID = 29050]
2. 1 eV [Option ID = 29049]
3. 1.45 eV [Option ID = 29051]
4. 0.05 eV [Option ID = 29052]
Correct Answer :-
1 eV [Option ID = 29049]
An ideal photodiode is made of a material with a bandgap energy of 2.35 eV. It operates at 300 K
and is illuminated by monochromatic light with wavelength of 400 nm. Its maximum efficiency is
[Question ID = 14772]
1. 80% [Option ID = 29088]
2. 25% [Option ID = 29085]
3. 75.7% [Option ID = 29086]
4. 48% [Option ID = 29087]
Correct Answer :-
25% [Option ID = 29085]
If line A of X-ray beam gives a first order reflection maxima at a glancing angle of 30? to the
smooth face of a crystal and line B of ? = 0.92 ? gives a third order reflection maxima at an angle 60?
from the face of same crystal, then the wavelength of line A is
[Question ID = 14769]
1. 3.36 ? [Option ID = 29073]
2. 6.72 ? [Option ID = 29076]
3. 0.84 ? [Option ID = 29075]
4. 1.59 ? [Option ID = 29074]
Correct Answer :-
3.36 ? [Option ID = 29073]
If ? = Kein? then the value of ?K? after normalization in the limits 0 to is
[Question ID = 15449]
5)
6)
7)
1. [Option ID = 31794]
2. [Option ID = 31793]
3. [Option ID = 31795]
4. [Option ID = 31796]
Correct Answer :-
[Option ID = 31793]
In a microwave test bench, a dip is shown on the CRO display by rotating the micrometer of
wavemeter, which indicates
[Question ID = 14785]
1. frequency of microwave signal is not same as frequency of wavemeter [Option ID = 29139]
2. frequency of microwave signal is zero [Option ID = 29137]
3. frequency of microwave signal is same as frequency of wavemeter [Option ID = 29138]
4. no signal propagates [Option ID = 29140]
Correct Answer :-
frequency of microwave signal is zero [Option ID = 29137]
In a p-type Si sample the hole concentration is 8 ? 10
15
/ cm
3
. The intrinsic carrier concentration
is 4 ? 10
10
/ cm
3
. The electron concentration is
[Question ID = 14766]
1. zero [Option ID = 29061]
2. 4 ? 10
10
/cm
3
[Option ID = 29062]
3. 1.5 ? 10
25
/cm
3
[Option ID = 29063]
4. 2 ? 10
5
/cm
3
[Option ID = 29064]
Correct Answer :-
zero [Option ID = 29061]
Sigma Electronics sells a microwave receiver (A) having an operating spot noise figure of 10 dB
when driven by a source with effective noise temperature 130 K. Deltalink (B) sells a receiver with a
standard spot noise figure of 6 dB when driven by a source with effective noise temperature 190 K.
Zebrotronics (C) sells a receiver with standard spot noise figure of 6 dB when driven by a source with
effective noise temperature 290 K. The best receiver to purchase is
[Question ID = 14782]
1. (A) [Option ID = 29125]
2. None [Option ID = 29128]
3. (C ) [Option ID = 29126]
4. (B) [Option ID = 29127]
Correct Answer :-
8)
9)
10)
11)
(A) [Option ID = 29125]
A silicon bar of 1?m long and 100 ?m
2
in cross-sectional area is doped with 10
17
cm
-3
Phosphorus.
The saturation velocity is 10
7
cm/sec. The current at 300 K with 10V applied is
[Question ID = 14762]
1. 0.16 A [Option ID = 29047]
2. 0.8 A [Option ID = 29048]
3. 0.5 A [Option ID = 29046]
4. 1.2 A [Option ID = 29045]
Correct Answer :-
1.2 A [Option ID = 29045]
A silicon PN junction diode under reverse bias has depletion region of width 20 ?m. Given, the
relative permittivity of silicon, ?
r
= 12.7 and the permittivity of free space ?
0
= 8.85 ? 10
-12
F/m. The
depletion capacitance of the diode per square meter is
[Question ID = 14767]
1. 7.65 ?F [Option ID = 29065]
2. 3 ?F [Option ID = 29067]
3. 8.15 ?F [Option ID = 29066]
4. 5.62 ?F [Option ID = 29068]
Correct Answer :-
7.65 ?F [Option ID = 29065]
A silica optical fiber with a core diameter large enough to be considered by ray theory analysis
has a core refractive index of 1.65 and a cladding refractive index of 1.52. The numerical aperture
(NA) of the fiber is
[Question ID = 14774]
1. 0.32 [Option ID = 29094]
2. 0.56 [Option ID = 29096]
3. 0.42 [Option ID = 29095]
4. 0.64 [Option ID = 29093]
Correct Answer :-
0.64 [Option ID = 29093]
A step-index fiber has numerical aperture (NA) of 0.16 and its core index (n
1
) = 1.45. If core
diameter = 0.6 cm and ? = 0.9 nm then normalized frequency of the fiber is _____
[Question ID = 14776]
1. 6.70 ? 10
3
Hz [Option ID = 29103]
2. 1.67 ? 10
3
Hz [Option ID = 29101]
3. 3.35 ? 10
3
Hz [Option ID = 29102]
4. 1.83 ? 10
3
Hz [Option ID = 29104]
Correct Answer :-
1.67 ? 10
3
Hz [Option ID = 29101]
12)
13)
14)
15)
A three level laser emits laser light near the centre of visible band. If E
2
- E
1
= 2.36 eV then the
wavelength of radiation is
[Question ID = 14777]
1. 550 nm [Option ID = 29105]
2. 670 nm [Option ID = 29107]
3. 620 nm [Option ID = 29108]
4. 450 nm [Option ID = 29106]
Correct Answer :-
550 nm [Option ID = 29105]
log(1 + x ) = _______________
[Question ID = 14750]
1. [Option ID = 28997]
2. [Option ID = 29000]
3. [Option ID = 28999]
4. [Option ID = 28998]
Correct Answer :-
[Option ID = 28997]
If the bandgap of GaAsP is 1.98 eV then the color of emitted light is
[Question ID = 14770]
1. Blue [Option ID = 29077]
2. Green [Option ID = 29078]
3. Yellow [Option ID = 29080]
4. Red [Option ID = 29079]
Correct Answer :-
Blue [Option ID = 29077]
A laser beam emerging from a laser tube operating at 800 nm has a cross-sectional diameter of 2
mm. The diameter of the beam at a distance of 1 km is approximately
[Question ID = 14779]
1. 10 cm [Option ID = 29116]
2. 10 mm [Option ID = 29113]
3. 80 cm [Option ID = 29114]
4. 8 cm [Option ID = 29115]
Correct Answer :-
10 mm [Option ID = 29113]
16)
17)
18)
19)
20)
A Si sample (n
i
= 1.5 ? 10
10
atoms/cm
3
) is doped with 10
17
As atoms/cm
3
. The position of E
f
related to E
i
is
[Question ID = 14761]
1. 0.895 eV [Option ID = 29043]
2. 0.407 eV [Option ID = 29044]
3. 0.532 eV [Option ID = 29042]
4. 0.217 eV [Option ID = 29041]
Correct Answer :-
0.217 eV [Option ID = 29041]
Attenuator reduces the microwave power in
[Question ID = 14783]
1. uni-direction [Option ID = 29130]
2. None of these [Option ID = 29132]
3. multi-direction [Option ID = 29131]
4. bi-direction [Option ID = 29129]
Correct Answer :-
bi-direction [Option ID = 29129]
A box contains 4 red balls and 6 black balls. Three balls are selected randomly from the box one
after another, without replacement. The probability that the selected set contains one red ball and
two black balls is
[Question ID = 14746]
1. 3/10 [Option ID = 28982]
2. 1/12 [Option ID = 28981]
3. 1/20 [Option ID = 28984]
4. 1/2 [Option ID = 28983]
Correct Answer :-
1/12 [Option ID = 28981]
Electron mobility in Si at room temperature (300 K) is 1400 cm
2
V
?1
s
?1
. The diffusion coefficient
of electrons is
[Question ID = 14765]
1. 36.22 cm
2
/s [Option ID = 29057]
2. 62.25 cm
2
/s [Option ID = 29059]
3. 32.76 cm
2
/s [Option ID = 29060]
4. 49.16 cm
2
/s [Option ID = 29058]
Correct Answer :-
36.22 cm
2
/s [Option ID = 29057]
In the Taylor series expansion of exp(x) + sin(x) about the point x = , the coefficient of (x -
)2 is
21)
22)
23)
24)
[Question ID = 15451]
1. 0.5 exp( ) [Option ID = 31802]
2. exp( ) [Option ID = 31801]
3. exp( ) - 1 [Option ID = 31804]
4. exp( ) + 1 [Option ID = 31803]
Correct Answer :-
exp( ) [Option ID = 31801]
In the expression 6 + 8i = 10e
i?
, the value of ? is,
[Question ID = 14743]
1. 85.16? [Option ID = 28971]
2. 53.13? [Option ID = 28972]
3. 36.16? [Option ID = 28970]
4. 13.13? [Option ID = 28969]
Correct Answer :-
13.13? [Option ID = 28969]
In the interval [0, ] the equation x = cos x
[Question ID = 15450]
1. exactly one solution [Option ID = 31799]
2. exactly two solutions [Option ID = 31797]
3. no solutions [Option ID = 31798]
4. an infinite number of solutions [Option ID = 31800]
Correct Answer :-
exactly two solutions [Option ID = 31797]
Choose the correct match out of the following options given below
Column I Column II
P. 2
nd
order DEs 1. Newton ? Raphson method
Q. Non-linear algebraic equations 2. Gauss Elimination
R. Linear algebraic equations 3. Simpson?s rule
S. Numerical integration 4. Runge-kutta method
[Question ID = 14754]
1. P->4 Q->1 R->2 S->3 [Option ID = 29014]
2. P->4 Q->2 R->3 S->1 [Option ID = 29015]
3. P->4 Q->2 R->1 S->3 [Option ID = 29016]
4. P->1 Q->2 R->3 S->4 [Option ID = 29013]
Correct Answer :-
P->1 Q->2 R->3 S->4 [Option ID = 29013]
Helical antenna has the following polarization
[Question ID = 14788]
25)
26)
27)
1. vertical [Option ID = 29152]
2. linear [Option ID = 29149]
3. elliptical [Option ID = 29151]
4. circular [Option ID = 29150]
Correct Answer :-
linear [Option ID = 29149]
Match the typical spectroscopic regions specified in Part-I with corresponding type of transitions
in Part-II and choose the correct answer from the following options.
Part-I Part-II
K. Infrared region 1. Electron transition involving valance electrons
L. Ultraviolet visible region 2. Nuclear transitions
M. X-ray region 3. Vibrational transitions of molecules
N. ?-ray region 4. Transitions involving inner shell electrons
[Question ID = 14775]
1. K->4 L->2 M->1 N->3 [Option ID = 29098]
2. K->3 L->4 M->1 N->2 [Option ID = 29100]
3. K->3 L->1 M->4 N->2 [Option ID = 29097]
4. K->1 L->2 M->3 N->4 [Option ID = 29099]
Correct Answer :-
K->3 L->1 M->4 N->2 [Option ID = 29097]
[Question ID = 14757]
1. [Option ID = 29027]
2. [Option ID = 29026]
3. [Option ID = 29025]
4. [Option ID = 29028]
Correct Answer :-
[Option ID = 29025]
[Question ID = 14755]
1. 3/5 [Option ID = 29018]
2. -5/2 [Option ID = 29017]
28)
29)
30)
31)
3. -5/3 [Option ID = 29020]
4. -2/5 [Option ID = 29019]
Correct Answer :-
-5/2 [Option ID = 29017]
[Question ID = 14756]
1. 1,0,2,3 [Option ID = 29021]
2. -1,1,0,3 [Option ID = 29024]
3. -1,1,0,2 [Option ID = 29023]
4. -2, -1, 1, 2 [Option ID = 29022]
Correct Answer :-
1,0,2,3 [Option ID = 29021]
[Question ID = 14747]
1. 20/3 [Option ID = 28987]
2. 40/3 [Option ID = 28986]
3. 0 [Option ID = 28988]
4. 4/3 [Option ID = 28985]
Correct Answer :-
4/3 [Option ID = 28985]
[Question ID = 14760]
1. 0.306 [Option ID = 29038]
2. 2.432 [Option ID = 29039]
3. 1.694 [Option ID = 29040]
4. 0.732 [Option ID = 29037]
Correct Answer :-
0.732 [Option ID = 29037]
32)
33)
34)
[Question ID = 14745]
1. [Option ID = 28979]
2. [Option ID = 28980]
3. [Option ID = 28977]
4. [Option ID = 28978]
Correct Answer :-
[Option ID = 28977]
[Question ID = 14751]
1. 1 [Option ID = 29004]
2. 1/4 [Option ID = 29002]
3. 1/12 [Option ID = 29001]
4. 0 [Option ID = 29003]
Correct Answer :-
1/12 [Option ID = 29001]
For an n-channel MOSFET with a gate oxide (?
r
= 3.9) thickness of 10 nm, V
th
= 0.6 V and W = 25
?m, L = 1 ?m and electron mobility in channel, ? = 200 cm
2
/V-s. The drain current at V
GS
= 5 V and
V
DS
= 0.1 V is
[Question ID = 14778]
1. 7.51 ? 10
-4
A [Option ID = 29111]
2. 3.05 ? 10
-5
A [Option ID = 29109]
3. 5.1 ? 10
-6
A [Option ID = 29110]
4. 8 ? 10
-5
A [Option ID = 29112]
Correct Answer :-
3.05 ? 10
-5
A [Option ID = 29109]
For z
6
+ z
3
+ 1 = 0 , the general solution is
[Question ID = 14744]
1. e
-4i?? /3
[Option ID = 28975]
FirstRanker.com - FirstRanker's Choice
1)
2)
3)
4)
DU PhD in Electronics
Topic:- DU_J19_PHD_ELEC
An electron beam with 3 eV energy strikes a crystal of cadmium sulfide (CdS) (bandgap E
g
=2.45
eV). Electrons scattered by the crystal move at a velocity of 4.4 ? 10
5
m/s. The scattered energy (in
eV) of the electrons is
[Question ID = 14763]
1. 0.55 eV [Option ID = 29050]
2. 1 eV [Option ID = 29049]
3. 1.45 eV [Option ID = 29051]
4. 0.05 eV [Option ID = 29052]
Correct Answer :-
1 eV [Option ID = 29049]
An ideal photodiode is made of a material with a bandgap energy of 2.35 eV. It operates at 300 K
and is illuminated by monochromatic light with wavelength of 400 nm. Its maximum efficiency is
[Question ID = 14772]
1. 80% [Option ID = 29088]
2. 25% [Option ID = 29085]
3. 75.7% [Option ID = 29086]
4. 48% [Option ID = 29087]
Correct Answer :-
25% [Option ID = 29085]
If line A of X-ray beam gives a first order reflection maxima at a glancing angle of 30? to the
smooth face of a crystal and line B of ? = 0.92 ? gives a third order reflection maxima at an angle 60?
from the face of same crystal, then the wavelength of line A is
[Question ID = 14769]
1. 3.36 ? [Option ID = 29073]
2. 6.72 ? [Option ID = 29076]
3. 0.84 ? [Option ID = 29075]
4. 1.59 ? [Option ID = 29074]
Correct Answer :-
3.36 ? [Option ID = 29073]
If ? = Kein? then the value of ?K? after normalization in the limits 0 to is
[Question ID = 15449]
5)
6)
7)
1. [Option ID = 31794]
2. [Option ID = 31793]
3. [Option ID = 31795]
4. [Option ID = 31796]
Correct Answer :-
[Option ID = 31793]
In a microwave test bench, a dip is shown on the CRO display by rotating the micrometer of
wavemeter, which indicates
[Question ID = 14785]
1. frequency of microwave signal is not same as frequency of wavemeter [Option ID = 29139]
2. frequency of microwave signal is zero [Option ID = 29137]
3. frequency of microwave signal is same as frequency of wavemeter [Option ID = 29138]
4. no signal propagates [Option ID = 29140]
Correct Answer :-
frequency of microwave signal is zero [Option ID = 29137]
In a p-type Si sample the hole concentration is 8 ? 10
15
/ cm
3
. The intrinsic carrier concentration
is 4 ? 10
10
/ cm
3
. The electron concentration is
[Question ID = 14766]
1. zero [Option ID = 29061]
2. 4 ? 10
10
/cm
3
[Option ID = 29062]
3. 1.5 ? 10
25
/cm
3
[Option ID = 29063]
4. 2 ? 10
5
/cm
3
[Option ID = 29064]
Correct Answer :-
zero [Option ID = 29061]
Sigma Electronics sells a microwave receiver (A) having an operating spot noise figure of 10 dB
when driven by a source with effective noise temperature 130 K. Deltalink (B) sells a receiver with a
standard spot noise figure of 6 dB when driven by a source with effective noise temperature 190 K.
Zebrotronics (C) sells a receiver with standard spot noise figure of 6 dB when driven by a source with
effective noise temperature 290 K. The best receiver to purchase is
[Question ID = 14782]
1. (A) [Option ID = 29125]
2. None [Option ID = 29128]
3. (C ) [Option ID = 29126]
4. (B) [Option ID = 29127]
Correct Answer :-
8)
9)
10)
11)
(A) [Option ID = 29125]
A silicon bar of 1?m long and 100 ?m
2
in cross-sectional area is doped with 10
17
cm
-3
Phosphorus.
The saturation velocity is 10
7
cm/sec. The current at 300 K with 10V applied is
[Question ID = 14762]
1. 0.16 A [Option ID = 29047]
2. 0.8 A [Option ID = 29048]
3. 0.5 A [Option ID = 29046]
4. 1.2 A [Option ID = 29045]
Correct Answer :-
1.2 A [Option ID = 29045]
A silicon PN junction diode under reverse bias has depletion region of width 20 ?m. Given, the
relative permittivity of silicon, ?
r
= 12.7 and the permittivity of free space ?
0
= 8.85 ? 10
-12
F/m. The
depletion capacitance of the diode per square meter is
[Question ID = 14767]
1. 7.65 ?F [Option ID = 29065]
2. 3 ?F [Option ID = 29067]
3. 8.15 ?F [Option ID = 29066]
4. 5.62 ?F [Option ID = 29068]
Correct Answer :-
7.65 ?F [Option ID = 29065]
A silica optical fiber with a core diameter large enough to be considered by ray theory analysis
has a core refractive index of 1.65 and a cladding refractive index of 1.52. The numerical aperture
(NA) of the fiber is
[Question ID = 14774]
1. 0.32 [Option ID = 29094]
2. 0.56 [Option ID = 29096]
3. 0.42 [Option ID = 29095]
4. 0.64 [Option ID = 29093]
Correct Answer :-
0.64 [Option ID = 29093]
A step-index fiber has numerical aperture (NA) of 0.16 and its core index (n
1
) = 1.45. If core
diameter = 0.6 cm and ? = 0.9 nm then normalized frequency of the fiber is _____
[Question ID = 14776]
1. 6.70 ? 10
3
Hz [Option ID = 29103]
2. 1.67 ? 10
3
Hz [Option ID = 29101]
3. 3.35 ? 10
3
Hz [Option ID = 29102]
4. 1.83 ? 10
3
Hz [Option ID = 29104]
Correct Answer :-
1.67 ? 10
3
Hz [Option ID = 29101]
12)
13)
14)
15)
A three level laser emits laser light near the centre of visible band. If E
2
- E
1
= 2.36 eV then the
wavelength of radiation is
[Question ID = 14777]
1. 550 nm [Option ID = 29105]
2. 670 nm [Option ID = 29107]
3. 620 nm [Option ID = 29108]
4. 450 nm [Option ID = 29106]
Correct Answer :-
550 nm [Option ID = 29105]
log(1 + x ) = _______________
[Question ID = 14750]
1. [Option ID = 28997]
2. [Option ID = 29000]
3. [Option ID = 28999]
4. [Option ID = 28998]
Correct Answer :-
[Option ID = 28997]
If the bandgap of GaAsP is 1.98 eV then the color of emitted light is
[Question ID = 14770]
1. Blue [Option ID = 29077]
2. Green [Option ID = 29078]
3. Yellow [Option ID = 29080]
4. Red [Option ID = 29079]
Correct Answer :-
Blue [Option ID = 29077]
A laser beam emerging from a laser tube operating at 800 nm has a cross-sectional diameter of 2
mm. The diameter of the beam at a distance of 1 km is approximately
[Question ID = 14779]
1. 10 cm [Option ID = 29116]
2. 10 mm [Option ID = 29113]
3. 80 cm [Option ID = 29114]
4. 8 cm [Option ID = 29115]
Correct Answer :-
10 mm [Option ID = 29113]
16)
17)
18)
19)
20)
A Si sample (n
i
= 1.5 ? 10
10
atoms/cm
3
) is doped with 10
17
As atoms/cm
3
. The position of E
f
related to E
i
is
[Question ID = 14761]
1. 0.895 eV [Option ID = 29043]
2. 0.407 eV [Option ID = 29044]
3. 0.532 eV [Option ID = 29042]
4. 0.217 eV [Option ID = 29041]
Correct Answer :-
0.217 eV [Option ID = 29041]
Attenuator reduces the microwave power in
[Question ID = 14783]
1. uni-direction [Option ID = 29130]
2. None of these [Option ID = 29132]
3. multi-direction [Option ID = 29131]
4. bi-direction [Option ID = 29129]
Correct Answer :-
bi-direction [Option ID = 29129]
A box contains 4 red balls and 6 black balls. Three balls are selected randomly from the box one
after another, without replacement. The probability that the selected set contains one red ball and
two black balls is
[Question ID = 14746]
1. 3/10 [Option ID = 28982]
2. 1/12 [Option ID = 28981]
3. 1/20 [Option ID = 28984]
4. 1/2 [Option ID = 28983]
Correct Answer :-
1/12 [Option ID = 28981]
Electron mobility in Si at room temperature (300 K) is 1400 cm
2
V
?1
s
?1
. The diffusion coefficient
of electrons is
[Question ID = 14765]
1. 36.22 cm
2
/s [Option ID = 29057]
2. 62.25 cm
2
/s [Option ID = 29059]
3. 32.76 cm
2
/s [Option ID = 29060]
4. 49.16 cm
2
/s [Option ID = 29058]
Correct Answer :-
36.22 cm
2
/s [Option ID = 29057]
In the Taylor series expansion of exp(x) + sin(x) about the point x = , the coefficient of (x -
)2 is
21)
22)
23)
24)
[Question ID = 15451]
1. 0.5 exp( ) [Option ID = 31802]
2. exp( ) [Option ID = 31801]
3. exp( ) - 1 [Option ID = 31804]
4. exp( ) + 1 [Option ID = 31803]
Correct Answer :-
exp( ) [Option ID = 31801]
In the expression 6 + 8i = 10e
i?
, the value of ? is,
[Question ID = 14743]
1. 85.16? [Option ID = 28971]
2. 53.13? [Option ID = 28972]
3. 36.16? [Option ID = 28970]
4. 13.13? [Option ID = 28969]
Correct Answer :-
13.13? [Option ID = 28969]
In the interval [0, ] the equation x = cos x
[Question ID = 15450]
1. exactly one solution [Option ID = 31799]
2. exactly two solutions [Option ID = 31797]
3. no solutions [Option ID = 31798]
4. an infinite number of solutions [Option ID = 31800]
Correct Answer :-
exactly two solutions [Option ID = 31797]
Choose the correct match out of the following options given below
Column I Column II
P. 2
nd
order DEs 1. Newton ? Raphson method
Q. Non-linear algebraic equations 2. Gauss Elimination
R. Linear algebraic equations 3. Simpson?s rule
S. Numerical integration 4. Runge-kutta method
[Question ID = 14754]
1. P->4 Q->1 R->2 S->3 [Option ID = 29014]
2. P->4 Q->2 R->3 S->1 [Option ID = 29015]
3. P->4 Q->2 R->1 S->3 [Option ID = 29016]
4. P->1 Q->2 R->3 S->4 [Option ID = 29013]
Correct Answer :-
P->1 Q->2 R->3 S->4 [Option ID = 29013]
Helical antenna has the following polarization
[Question ID = 14788]
25)
26)
27)
1. vertical [Option ID = 29152]
2. linear [Option ID = 29149]
3. elliptical [Option ID = 29151]
4. circular [Option ID = 29150]
Correct Answer :-
linear [Option ID = 29149]
Match the typical spectroscopic regions specified in Part-I with corresponding type of transitions
in Part-II and choose the correct answer from the following options.
Part-I Part-II
K. Infrared region 1. Electron transition involving valance electrons
L. Ultraviolet visible region 2. Nuclear transitions
M. X-ray region 3. Vibrational transitions of molecules
N. ?-ray region 4. Transitions involving inner shell electrons
[Question ID = 14775]
1. K->4 L->2 M->1 N->3 [Option ID = 29098]
2. K->3 L->4 M->1 N->2 [Option ID = 29100]
3. K->3 L->1 M->4 N->2 [Option ID = 29097]
4. K->1 L->2 M->3 N->4 [Option ID = 29099]
Correct Answer :-
K->3 L->1 M->4 N->2 [Option ID = 29097]
[Question ID = 14757]
1. [Option ID = 29027]
2. [Option ID = 29026]
3. [Option ID = 29025]
4. [Option ID = 29028]
Correct Answer :-
[Option ID = 29025]
[Question ID = 14755]
1. 3/5 [Option ID = 29018]
2. -5/2 [Option ID = 29017]
28)
29)
30)
31)
3. -5/3 [Option ID = 29020]
4. -2/5 [Option ID = 29019]
Correct Answer :-
-5/2 [Option ID = 29017]
[Question ID = 14756]
1. 1,0,2,3 [Option ID = 29021]
2. -1,1,0,3 [Option ID = 29024]
3. -1,1,0,2 [Option ID = 29023]
4. -2, -1, 1, 2 [Option ID = 29022]
Correct Answer :-
1,0,2,3 [Option ID = 29021]
[Question ID = 14747]
1. 20/3 [Option ID = 28987]
2. 40/3 [Option ID = 28986]
3. 0 [Option ID = 28988]
4. 4/3 [Option ID = 28985]
Correct Answer :-
4/3 [Option ID = 28985]
[Question ID = 14760]
1. 0.306 [Option ID = 29038]
2. 2.432 [Option ID = 29039]
3. 1.694 [Option ID = 29040]
4. 0.732 [Option ID = 29037]
Correct Answer :-
0.732 [Option ID = 29037]
32)
33)
34)
[Question ID = 14745]
1. [Option ID = 28979]
2. [Option ID = 28980]
3. [Option ID = 28977]
4. [Option ID = 28978]
Correct Answer :-
[Option ID = 28977]
[Question ID = 14751]
1. 1 [Option ID = 29004]
2. 1/4 [Option ID = 29002]
3. 1/12 [Option ID = 29001]
4. 0 [Option ID = 29003]
Correct Answer :-
1/12 [Option ID = 29001]
For an n-channel MOSFET with a gate oxide (?
r
= 3.9) thickness of 10 nm, V
th
= 0.6 V and W = 25
?m, L = 1 ?m and electron mobility in channel, ? = 200 cm
2
/V-s. The drain current at V
GS
= 5 V and
V
DS
= 0.1 V is
[Question ID = 14778]
1. 7.51 ? 10
-4
A [Option ID = 29111]
2. 3.05 ? 10
-5
A [Option ID = 29109]
3. 5.1 ? 10
-6
A [Option ID = 29110]
4. 8 ? 10
-5
A [Option ID = 29112]
Correct Answer :-
3.05 ? 10
-5
A [Option ID = 29109]
For z
6
+ z
3
+ 1 = 0 , the general solution is
[Question ID = 14744]
1. e
-4i?? /3
[Option ID = 28975]
35)
36)
37)
38)
2. e
-i?? /3
[Option ID = 28976]
3. e
i?? /3
[Option ID = 28974]
4. e
2i?? /3
[Option ID = 28973]
Correct Answer :-
e
2i?? /3
[Option ID = 28973]
A small concentration of minority carriers is injected into a homogeneous Semiconductor crystal
at one point. An electric field of 10 V/cm is applied across the crystal and this moves the minority
carriers by a distance of 1 cm in 20 ?sec. The mobility (in cm
2
/v-sec) of carriers is
[Question ID = 14768]
1. 5000 [Option ID = 29072]
2. 2000 [Option ID = 29069]
3. 4000 [Option ID = 29071]
4. 3000 [Option ID = 29070]
Correct Answer :-
2000 [Option ID = 29069]
Let the continuous random variable X denote the current measured in a thin copper wire in milli
amperes (mA). Assume that the range of X is 4.9 ? x ? 5.1 and f(x) = 5. The probability that a current
is less than 5mA is
[Question ID = 14748]
1. 0.4 [Option ID = 28990]
2. 0.2 [Option ID = 28992]
3. 0.5 [Option ID = 28989]
4. 0.3 [Option ID = 28991]
Correct Answer :-
0.5 [Option ID = 28989]
A transmission line has a characteristic impedance of 75 ? and a resistance of 5 ?/m. If the line
is distortion less, the attenuation constant (in Np/m) is
[Question ID = 14792]
1. 0.066 [Option ID = 29167]
2. 0.033 [Option ID = 29168]
3. 0.022 [Option ID = 29165]
4. 0.055 [Option ID = 29166]
Correct Answer :-
0.022 [Option ID = 29165]
A transmitting antenna with a 300 MHz carrier frequency produces 4 kW of power. If both
antennas has unity power gain, the power received by another antenna at a distance of 2 km is
[Question ID = 14791]
1. 8.44 mW [Option ID = 29161]
2. 4.4 ?W [Option ID = 29163]
3. 11.8 mW [Option ID = 29162]
FirstRanker.com - FirstRanker's Choice
1)
2)
3)
4)
DU PhD in Electronics
Topic:- DU_J19_PHD_ELEC
An electron beam with 3 eV energy strikes a crystal of cadmium sulfide (CdS) (bandgap E
g
=2.45
eV). Electrons scattered by the crystal move at a velocity of 4.4 ? 10
5
m/s. The scattered energy (in
eV) of the electrons is
[Question ID = 14763]
1. 0.55 eV [Option ID = 29050]
2. 1 eV [Option ID = 29049]
3. 1.45 eV [Option ID = 29051]
4. 0.05 eV [Option ID = 29052]
Correct Answer :-
1 eV [Option ID = 29049]
An ideal photodiode is made of a material with a bandgap energy of 2.35 eV. It operates at 300 K
and is illuminated by monochromatic light with wavelength of 400 nm. Its maximum efficiency is
[Question ID = 14772]
1. 80% [Option ID = 29088]
2. 25% [Option ID = 29085]
3. 75.7% [Option ID = 29086]
4. 48% [Option ID = 29087]
Correct Answer :-
25% [Option ID = 29085]
If line A of X-ray beam gives a first order reflection maxima at a glancing angle of 30? to the
smooth face of a crystal and line B of ? = 0.92 ? gives a third order reflection maxima at an angle 60?
from the face of same crystal, then the wavelength of line A is
[Question ID = 14769]
1. 3.36 ? [Option ID = 29073]
2. 6.72 ? [Option ID = 29076]
3. 0.84 ? [Option ID = 29075]
4. 1.59 ? [Option ID = 29074]
Correct Answer :-
3.36 ? [Option ID = 29073]
If ? = Kein? then the value of ?K? after normalization in the limits 0 to is
[Question ID = 15449]
5)
6)
7)
1. [Option ID = 31794]
2. [Option ID = 31793]
3. [Option ID = 31795]
4. [Option ID = 31796]
Correct Answer :-
[Option ID = 31793]
In a microwave test bench, a dip is shown on the CRO display by rotating the micrometer of
wavemeter, which indicates
[Question ID = 14785]
1. frequency of microwave signal is not same as frequency of wavemeter [Option ID = 29139]
2. frequency of microwave signal is zero [Option ID = 29137]
3. frequency of microwave signal is same as frequency of wavemeter [Option ID = 29138]
4. no signal propagates [Option ID = 29140]
Correct Answer :-
frequency of microwave signal is zero [Option ID = 29137]
In a p-type Si sample the hole concentration is 8 ? 10
15
/ cm
3
. The intrinsic carrier concentration
is 4 ? 10
10
/ cm
3
. The electron concentration is
[Question ID = 14766]
1. zero [Option ID = 29061]
2. 4 ? 10
10
/cm
3
[Option ID = 29062]
3. 1.5 ? 10
25
/cm
3
[Option ID = 29063]
4. 2 ? 10
5
/cm
3
[Option ID = 29064]
Correct Answer :-
zero [Option ID = 29061]
Sigma Electronics sells a microwave receiver (A) having an operating spot noise figure of 10 dB
when driven by a source with effective noise temperature 130 K. Deltalink (B) sells a receiver with a
standard spot noise figure of 6 dB when driven by a source with effective noise temperature 190 K.
Zebrotronics (C) sells a receiver with standard spot noise figure of 6 dB when driven by a source with
effective noise temperature 290 K. The best receiver to purchase is
[Question ID = 14782]
1. (A) [Option ID = 29125]
2. None [Option ID = 29128]
3. (C ) [Option ID = 29126]
4. (B) [Option ID = 29127]
Correct Answer :-
8)
9)
10)
11)
(A) [Option ID = 29125]
A silicon bar of 1?m long and 100 ?m
2
in cross-sectional area is doped with 10
17
cm
-3
Phosphorus.
The saturation velocity is 10
7
cm/sec. The current at 300 K with 10V applied is
[Question ID = 14762]
1. 0.16 A [Option ID = 29047]
2. 0.8 A [Option ID = 29048]
3. 0.5 A [Option ID = 29046]
4. 1.2 A [Option ID = 29045]
Correct Answer :-
1.2 A [Option ID = 29045]
A silicon PN junction diode under reverse bias has depletion region of width 20 ?m. Given, the
relative permittivity of silicon, ?
r
= 12.7 and the permittivity of free space ?
0
= 8.85 ? 10
-12
F/m. The
depletion capacitance of the diode per square meter is
[Question ID = 14767]
1. 7.65 ?F [Option ID = 29065]
2. 3 ?F [Option ID = 29067]
3. 8.15 ?F [Option ID = 29066]
4. 5.62 ?F [Option ID = 29068]
Correct Answer :-
7.65 ?F [Option ID = 29065]
A silica optical fiber with a core diameter large enough to be considered by ray theory analysis
has a core refractive index of 1.65 and a cladding refractive index of 1.52. The numerical aperture
(NA) of the fiber is
[Question ID = 14774]
1. 0.32 [Option ID = 29094]
2. 0.56 [Option ID = 29096]
3. 0.42 [Option ID = 29095]
4. 0.64 [Option ID = 29093]
Correct Answer :-
0.64 [Option ID = 29093]
A step-index fiber has numerical aperture (NA) of 0.16 and its core index (n
1
) = 1.45. If core
diameter = 0.6 cm and ? = 0.9 nm then normalized frequency of the fiber is _____
[Question ID = 14776]
1. 6.70 ? 10
3
Hz [Option ID = 29103]
2. 1.67 ? 10
3
Hz [Option ID = 29101]
3. 3.35 ? 10
3
Hz [Option ID = 29102]
4. 1.83 ? 10
3
Hz [Option ID = 29104]
Correct Answer :-
1.67 ? 10
3
Hz [Option ID = 29101]
12)
13)
14)
15)
A three level laser emits laser light near the centre of visible band. If E
2
- E
1
= 2.36 eV then the
wavelength of radiation is
[Question ID = 14777]
1. 550 nm [Option ID = 29105]
2. 670 nm [Option ID = 29107]
3. 620 nm [Option ID = 29108]
4. 450 nm [Option ID = 29106]
Correct Answer :-
550 nm [Option ID = 29105]
log(1 + x ) = _______________
[Question ID = 14750]
1. [Option ID = 28997]
2. [Option ID = 29000]
3. [Option ID = 28999]
4. [Option ID = 28998]
Correct Answer :-
[Option ID = 28997]
If the bandgap of GaAsP is 1.98 eV then the color of emitted light is
[Question ID = 14770]
1. Blue [Option ID = 29077]
2. Green [Option ID = 29078]
3. Yellow [Option ID = 29080]
4. Red [Option ID = 29079]
Correct Answer :-
Blue [Option ID = 29077]
A laser beam emerging from a laser tube operating at 800 nm has a cross-sectional diameter of 2
mm. The diameter of the beam at a distance of 1 km is approximately
[Question ID = 14779]
1. 10 cm [Option ID = 29116]
2. 10 mm [Option ID = 29113]
3. 80 cm [Option ID = 29114]
4. 8 cm [Option ID = 29115]
Correct Answer :-
10 mm [Option ID = 29113]
16)
17)
18)
19)
20)
A Si sample (n
i
= 1.5 ? 10
10
atoms/cm
3
) is doped with 10
17
As atoms/cm
3
. The position of E
f
related to E
i
is
[Question ID = 14761]
1. 0.895 eV [Option ID = 29043]
2. 0.407 eV [Option ID = 29044]
3. 0.532 eV [Option ID = 29042]
4. 0.217 eV [Option ID = 29041]
Correct Answer :-
0.217 eV [Option ID = 29041]
Attenuator reduces the microwave power in
[Question ID = 14783]
1. uni-direction [Option ID = 29130]
2. None of these [Option ID = 29132]
3. multi-direction [Option ID = 29131]
4. bi-direction [Option ID = 29129]
Correct Answer :-
bi-direction [Option ID = 29129]
A box contains 4 red balls and 6 black balls. Three balls are selected randomly from the box one
after another, without replacement. The probability that the selected set contains one red ball and
two black balls is
[Question ID = 14746]
1. 3/10 [Option ID = 28982]
2. 1/12 [Option ID = 28981]
3. 1/20 [Option ID = 28984]
4. 1/2 [Option ID = 28983]
Correct Answer :-
1/12 [Option ID = 28981]
Electron mobility in Si at room temperature (300 K) is 1400 cm
2
V
?1
s
?1
. The diffusion coefficient
of electrons is
[Question ID = 14765]
1. 36.22 cm
2
/s [Option ID = 29057]
2. 62.25 cm
2
/s [Option ID = 29059]
3. 32.76 cm
2
/s [Option ID = 29060]
4. 49.16 cm
2
/s [Option ID = 29058]
Correct Answer :-
36.22 cm
2
/s [Option ID = 29057]
In the Taylor series expansion of exp(x) + sin(x) about the point x = , the coefficient of (x -
)2 is
21)
22)
23)
24)
[Question ID = 15451]
1. 0.5 exp( ) [Option ID = 31802]
2. exp( ) [Option ID = 31801]
3. exp( ) - 1 [Option ID = 31804]
4. exp( ) + 1 [Option ID = 31803]
Correct Answer :-
exp( ) [Option ID = 31801]
In the expression 6 + 8i = 10e
i?
, the value of ? is,
[Question ID = 14743]
1. 85.16? [Option ID = 28971]
2. 53.13? [Option ID = 28972]
3. 36.16? [Option ID = 28970]
4. 13.13? [Option ID = 28969]
Correct Answer :-
13.13? [Option ID = 28969]
In the interval [0, ] the equation x = cos x
[Question ID = 15450]
1. exactly one solution [Option ID = 31799]
2. exactly two solutions [Option ID = 31797]
3. no solutions [Option ID = 31798]
4. an infinite number of solutions [Option ID = 31800]
Correct Answer :-
exactly two solutions [Option ID = 31797]
Choose the correct match out of the following options given below
Column I Column II
P. 2
nd
order DEs 1. Newton ? Raphson method
Q. Non-linear algebraic equations 2. Gauss Elimination
R. Linear algebraic equations 3. Simpson?s rule
S. Numerical integration 4. Runge-kutta method
[Question ID = 14754]
1. P->4 Q->1 R->2 S->3 [Option ID = 29014]
2. P->4 Q->2 R->3 S->1 [Option ID = 29015]
3. P->4 Q->2 R->1 S->3 [Option ID = 29016]
4. P->1 Q->2 R->3 S->4 [Option ID = 29013]
Correct Answer :-
P->1 Q->2 R->3 S->4 [Option ID = 29013]
Helical antenna has the following polarization
[Question ID = 14788]
25)
26)
27)
1. vertical [Option ID = 29152]
2. linear [Option ID = 29149]
3. elliptical [Option ID = 29151]
4. circular [Option ID = 29150]
Correct Answer :-
linear [Option ID = 29149]
Match the typical spectroscopic regions specified in Part-I with corresponding type of transitions
in Part-II and choose the correct answer from the following options.
Part-I Part-II
K. Infrared region 1. Electron transition involving valance electrons
L. Ultraviolet visible region 2. Nuclear transitions
M. X-ray region 3. Vibrational transitions of molecules
N. ?-ray region 4. Transitions involving inner shell electrons
[Question ID = 14775]
1. K->4 L->2 M->1 N->3 [Option ID = 29098]
2. K->3 L->4 M->1 N->2 [Option ID = 29100]
3. K->3 L->1 M->4 N->2 [Option ID = 29097]
4. K->1 L->2 M->3 N->4 [Option ID = 29099]
Correct Answer :-
K->3 L->1 M->4 N->2 [Option ID = 29097]
[Question ID = 14757]
1. [Option ID = 29027]
2. [Option ID = 29026]
3. [Option ID = 29025]
4. [Option ID = 29028]
Correct Answer :-
[Option ID = 29025]
[Question ID = 14755]
1. 3/5 [Option ID = 29018]
2. -5/2 [Option ID = 29017]
28)
29)
30)
31)
3. -5/3 [Option ID = 29020]
4. -2/5 [Option ID = 29019]
Correct Answer :-
-5/2 [Option ID = 29017]
[Question ID = 14756]
1. 1,0,2,3 [Option ID = 29021]
2. -1,1,0,3 [Option ID = 29024]
3. -1,1,0,2 [Option ID = 29023]
4. -2, -1, 1, 2 [Option ID = 29022]
Correct Answer :-
1,0,2,3 [Option ID = 29021]
[Question ID = 14747]
1. 20/3 [Option ID = 28987]
2. 40/3 [Option ID = 28986]
3. 0 [Option ID = 28988]
4. 4/3 [Option ID = 28985]
Correct Answer :-
4/3 [Option ID = 28985]
[Question ID = 14760]
1. 0.306 [Option ID = 29038]
2. 2.432 [Option ID = 29039]
3. 1.694 [Option ID = 29040]
4. 0.732 [Option ID = 29037]
Correct Answer :-
0.732 [Option ID = 29037]
32)
33)
34)
[Question ID = 14745]
1. [Option ID = 28979]
2. [Option ID = 28980]
3. [Option ID = 28977]
4. [Option ID = 28978]
Correct Answer :-
[Option ID = 28977]
[Question ID = 14751]
1. 1 [Option ID = 29004]
2. 1/4 [Option ID = 29002]
3. 1/12 [Option ID = 29001]
4. 0 [Option ID = 29003]
Correct Answer :-
1/12 [Option ID = 29001]
For an n-channel MOSFET with a gate oxide (?
r
= 3.9) thickness of 10 nm, V
th
= 0.6 V and W = 25
?m, L = 1 ?m and electron mobility in channel, ? = 200 cm
2
/V-s. The drain current at V
GS
= 5 V and
V
DS
= 0.1 V is
[Question ID = 14778]
1. 7.51 ? 10
-4
A [Option ID = 29111]
2. 3.05 ? 10
-5
A [Option ID = 29109]
3. 5.1 ? 10
-6
A [Option ID = 29110]
4. 8 ? 10
-5
A [Option ID = 29112]
Correct Answer :-
3.05 ? 10
-5
A [Option ID = 29109]
For z
6
+ z
3
+ 1 = 0 , the general solution is
[Question ID = 14744]
1. e
-4i?? /3
[Option ID = 28975]
35)
36)
37)
38)
2. e
-i?? /3
[Option ID = 28976]
3. e
i?? /3
[Option ID = 28974]
4. e
2i?? /3
[Option ID = 28973]
Correct Answer :-
e
2i?? /3
[Option ID = 28973]
A small concentration of minority carriers is injected into a homogeneous Semiconductor crystal
at one point. An electric field of 10 V/cm is applied across the crystal and this moves the minority
carriers by a distance of 1 cm in 20 ?sec. The mobility (in cm
2
/v-sec) of carriers is
[Question ID = 14768]
1. 5000 [Option ID = 29072]
2. 2000 [Option ID = 29069]
3. 4000 [Option ID = 29071]
4. 3000 [Option ID = 29070]
Correct Answer :-
2000 [Option ID = 29069]
Let the continuous random variable X denote the current measured in a thin copper wire in milli
amperes (mA). Assume that the range of X is 4.9 ? x ? 5.1 and f(x) = 5. The probability that a current
is less than 5mA is
[Question ID = 14748]
1. 0.4 [Option ID = 28990]
2. 0.2 [Option ID = 28992]
3. 0.5 [Option ID = 28989]
4. 0.3 [Option ID = 28991]
Correct Answer :-
0.5 [Option ID = 28989]
A transmission line has a characteristic impedance of 75 ? and a resistance of 5 ?/m. If the line
is distortion less, the attenuation constant (in Np/m) is
[Question ID = 14792]
1. 0.066 [Option ID = 29167]
2. 0.033 [Option ID = 29168]
3. 0.022 [Option ID = 29165]
4. 0.055 [Option ID = 29166]
Correct Answer :-
0.022 [Option ID = 29165]
A transmitting antenna with a 300 MHz carrier frequency produces 4 kW of power. If both
antennas has unity power gain, the power received by another antenna at a distance of 2 km is
[Question ID = 14791]
1. 8.44 mW [Option ID = 29161]
2. 4.4 ?W [Option ID = 29163]
3. 11.8 mW [Option ID = 29162]
39)
40)
41)
42)
4. 6.33 ?W [Option ID = 29164]
Correct Answer :-
8.44 mW [Option ID = 29161]
The power in power meter is displayed as -25 dB, when connected at the output of 30 dB
attenuator. The input power applied to this attenuator is
[Question ID = 14789]
1. 10.2 mW [Option ID = 29154]
2. 3.16 mW [Option ID = 29156]
3. 1.5 mW [Option ID = 29155]
4. 5 mW [Option ID = 29153]
Correct Answer :-
5 mW [Option ID = 29153]
The short-circuit current delivered by a 10 cm by 10 cm photocell (with 100% quantum
efficiency) illuminated by monochromatic light of 400 nm wavelength with a power density of 1000
W/m
2
is
[Question ID = 14773]
1. 6.85A [Option ID = 29092]
2. 5A [Option ID = 29089]
3. 8.32A [Option ID = 29091]
4. 3.2A [Option ID = 29090]
Correct Answer :-
5A [Option ID = 29089]
The recursion relation to solve x - e
-x
using Newton Raphson method is
[Question ID = 14758]
1. [Option ID = 29029]
2. [Option ID = 29030]
3. [Option ID = 29032]
4. [Option ID = 29031]
Correct Answer :-
[Option ID = 29029]
The temperature required to generate electron-hole pairs in silicon (E
g
= 1.1 eV) is (given
electron charge=1.6 ? 10
-19
J, Boltzman constant k =1.38 ? 10
-23
J/?K)
[Question ID = 14764]
FirstRanker.com - FirstRanker's Choice
1)
2)
3)
4)
DU PhD in Electronics
Topic:- DU_J19_PHD_ELEC
An electron beam with 3 eV energy strikes a crystal of cadmium sulfide (CdS) (bandgap E
g
=2.45
eV). Electrons scattered by the crystal move at a velocity of 4.4 ? 10
5
m/s. The scattered energy (in
eV) of the electrons is
[Question ID = 14763]
1. 0.55 eV [Option ID = 29050]
2. 1 eV [Option ID = 29049]
3. 1.45 eV [Option ID = 29051]
4. 0.05 eV [Option ID = 29052]
Correct Answer :-
1 eV [Option ID = 29049]
An ideal photodiode is made of a material with a bandgap energy of 2.35 eV. It operates at 300 K
and is illuminated by monochromatic light with wavelength of 400 nm. Its maximum efficiency is
[Question ID = 14772]
1. 80% [Option ID = 29088]
2. 25% [Option ID = 29085]
3. 75.7% [Option ID = 29086]
4. 48% [Option ID = 29087]
Correct Answer :-
25% [Option ID = 29085]
If line A of X-ray beam gives a first order reflection maxima at a glancing angle of 30? to the
smooth face of a crystal and line B of ? = 0.92 ? gives a third order reflection maxima at an angle 60?
from the face of same crystal, then the wavelength of line A is
[Question ID = 14769]
1. 3.36 ? [Option ID = 29073]
2. 6.72 ? [Option ID = 29076]
3. 0.84 ? [Option ID = 29075]
4. 1.59 ? [Option ID = 29074]
Correct Answer :-
3.36 ? [Option ID = 29073]
If ? = Kein? then the value of ?K? after normalization in the limits 0 to is
[Question ID = 15449]
5)
6)
7)
1. [Option ID = 31794]
2. [Option ID = 31793]
3. [Option ID = 31795]
4. [Option ID = 31796]
Correct Answer :-
[Option ID = 31793]
In a microwave test bench, a dip is shown on the CRO display by rotating the micrometer of
wavemeter, which indicates
[Question ID = 14785]
1. frequency of microwave signal is not same as frequency of wavemeter [Option ID = 29139]
2. frequency of microwave signal is zero [Option ID = 29137]
3. frequency of microwave signal is same as frequency of wavemeter [Option ID = 29138]
4. no signal propagates [Option ID = 29140]
Correct Answer :-
frequency of microwave signal is zero [Option ID = 29137]
In a p-type Si sample the hole concentration is 8 ? 10
15
/ cm
3
. The intrinsic carrier concentration
is 4 ? 10
10
/ cm
3
. The electron concentration is
[Question ID = 14766]
1. zero [Option ID = 29061]
2. 4 ? 10
10
/cm
3
[Option ID = 29062]
3. 1.5 ? 10
25
/cm
3
[Option ID = 29063]
4. 2 ? 10
5
/cm
3
[Option ID = 29064]
Correct Answer :-
zero [Option ID = 29061]
Sigma Electronics sells a microwave receiver (A) having an operating spot noise figure of 10 dB
when driven by a source with effective noise temperature 130 K. Deltalink (B) sells a receiver with a
standard spot noise figure of 6 dB when driven by a source with effective noise temperature 190 K.
Zebrotronics (C) sells a receiver with standard spot noise figure of 6 dB when driven by a source with
effective noise temperature 290 K. The best receiver to purchase is
[Question ID = 14782]
1. (A) [Option ID = 29125]
2. None [Option ID = 29128]
3. (C ) [Option ID = 29126]
4. (B) [Option ID = 29127]
Correct Answer :-
8)
9)
10)
11)
(A) [Option ID = 29125]
A silicon bar of 1?m long and 100 ?m
2
in cross-sectional area is doped with 10
17
cm
-3
Phosphorus.
The saturation velocity is 10
7
cm/sec. The current at 300 K with 10V applied is
[Question ID = 14762]
1. 0.16 A [Option ID = 29047]
2. 0.8 A [Option ID = 29048]
3. 0.5 A [Option ID = 29046]
4. 1.2 A [Option ID = 29045]
Correct Answer :-
1.2 A [Option ID = 29045]
A silicon PN junction diode under reverse bias has depletion region of width 20 ?m. Given, the
relative permittivity of silicon, ?
r
= 12.7 and the permittivity of free space ?
0
= 8.85 ? 10
-12
F/m. The
depletion capacitance of the diode per square meter is
[Question ID = 14767]
1. 7.65 ?F [Option ID = 29065]
2. 3 ?F [Option ID = 29067]
3. 8.15 ?F [Option ID = 29066]
4. 5.62 ?F [Option ID = 29068]
Correct Answer :-
7.65 ?F [Option ID = 29065]
A silica optical fiber with a core diameter large enough to be considered by ray theory analysis
has a core refractive index of 1.65 and a cladding refractive index of 1.52. The numerical aperture
(NA) of the fiber is
[Question ID = 14774]
1. 0.32 [Option ID = 29094]
2. 0.56 [Option ID = 29096]
3. 0.42 [Option ID = 29095]
4. 0.64 [Option ID = 29093]
Correct Answer :-
0.64 [Option ID = 29093]
A step-index fiber has numerical aperture (NA) of 0.16 and its core index (n
1
) = 1.45. If core
diameter = 0.6 cm and ? = 0.9 nm then normalized frequency of the fiber is _____
[Question ID = 14776]
1. 6.70 ? 10
3
Hz [Option ID = 29103]
2. 1.67 ? 10
3
Hz [Option ID = 29101]
3. 3.35 ? 10
3
Hz [Option ID = 29102]
4. 1.83 ? 10
3
Hz [Option ID = 29104]
Correct Answer :-
1.67 ? 10
3
Hz [Option ID = 29101]
12)
13)
14)
15)
A three level laser emits laser light near the centre of visible band. If E
2
- E
1
= 2.36 eV then the
wavelength of radiation is
[Question ID = 14777]
1. 550 nm [Option ID = 29105]
2. 670 nm [Option ID = 29107]
3. 620 nm [Option ID = 29108]
4. 450 nm [Option ID = 29106]
Correct Answer :-
550 nm [Option ID = 29105]
log(1 + x ) = _______________
[Question ID = 14750]
1. [Option ID = 28997]
2. [Option ID = 29000]
3. [Option ID = 28999]
4. [Option ID = 28998]
Correct Answer :-
[Option ID = 28997]
If the bandgap of GaAsP is 1.98 eV then the color of emitted light is
[Question ID = 14770]
1. Blue [Option ID = 29077]
2. Green [Option ID = 29078]
3. Yellow [Option ID = 29080]
4. Red [Option ID = 29079]
Correct Answer :-
Blue [Option ID = 29077]
A laser beam emerging from a laser tube operating at 800 nm has a cross-sectional diameter of 2
mm. The diameter of the beam at a distance of 1 km is approximately
[Question ID = 14779]
1. 10 cm [Option ID = 29116]
2. 10 mm [Option ID = 29113]
3. 80 cm [Option ID = 29114]
4. 8 cm [Option ID = 29115]
Correct Answer :-
10 mm [Option ID = 29113]
16)
17)
18)
19)
20)
A Si sample (n
i
= 1.5 ? 10
10
atoms/cm
3
) is doped with 10
17
As atoms/cm
3
. The position of E
f
related to E
i
is
[Question ID = 14761]
1. 0.895 eV [Option ID = 29043]
2. 0.407 eV [Option ID = 29044]
3. 0.532 eV [Option ID = 29042]
4. 0.217 eV [Option ID = 29041]
Correct Answer :-
0.217 eV [Option ID = 29041]
Attenuator reduces the microwave power in
[Question ID = 14783]
1. uni-direction [Option ID = 29130]
2. None of these [Option ID = 29132]
3. multi-direction [Option ID = 29131]
4. bi-direction [Option ID = 29129]
Correct Answer :-
bi-direction [Option ID = 29129]
A box contains 4 red balls and 6 black balls. Three balls are selected randomly from the box one
after another, without replacement. The probability that the selected set contains one red ball and
two black balls is
[Question ID = 14746]
1. 3/10 [Option ID = 28982]
2. 1/12 [Option ID = 28981]
3. 1/20 [Option ID = 28984]
4. 1/2 [Option ID = 28983]
Correct Answer :-
1/12 [Option ID = 28981]
Electron mobility in Si at room temperature (300 K) is 1400 cm
2
V
?1
s
?1
. The diffusion coefficient
of electrons is
[Question ID = 14765]
1. 36.22 cm
2
/s [Option ID = 29057]
2. 62.25 cm
2
/s [Option ID = 29059]
3. 32.76 cm
2
/s [Option ID = 29060]
4. 49.16 cm
2
/s [Option ID = 29058]
Correct Answer :-
36.22 cm
2
/s [Option ID = 29057]
In the Taylor series expansion of exp(x) + sin(x) about the point x = , the coefficient of (x -
)2 is
21)
22)
23)
24)
[Question ID = 15451]
1. 0.5 exp( ) [Option ID = 31802]
2. exp( ) [Option ID = 31801]
3. exp( ) - 1 [Option ID = 31804]
4. exp( ) + 1 [Option ID = 31803]
Correct Answer :-
exp( ) [Option ID = 31801]
In the expression 6 + 8i = 10e
i?
, the value of ? is,
[Question ID = 14743]
1. 85.16? [Option ID = 28971]
2. 53.13? [Option ID = 28972]
3. 36.16? [Option ID = 28970]
4. 13.13? [Option ID = 28969]
Correct Answer :-
13.13? [Option ID = 28969]
In the interval [0, ] the equation x = cos x
[Question ID = 15450]
1. exactly one solution [Option ID = 31799]
2. exactly two solutions [Option ID = 31797]
3. no solutions [Option ID = 31798]
4. an infinite number of solutions [Option ID = 31800]
Correct Answer :-
exactly two solutions [Option ID = 31797]
Choose the correct match out of the following options given below
Column I Column II
P. 2
nd
order DEs 1. Newton ? Raphson method
Q. Non-linear algebraic equations 2. Gauss Elimination
R. Linear algebraic equations 3. Simpson?s rule
S. Numerical integration 4. Runge-kutta method
[Question ID = 14754]
1. P->4 Q->1 R->2 S->3 [Option ID = 29014]
2. P->4 Q->2 R->3 S->1 [Option ID = 29015]
3. P->4 Q->2 R->1 S->3 [Option ID = 29016]
4. P->1 Q->2 R->3 S->4 [Option ID = 29013]
Correct Answer :-
P->1 Q->2 R->3 S->4 [Option ID = 29013]
Helical antenna has the following polarization
[Question ID = 14788]
25)
26)
27)
1. vertical [Option ID = 29152]
2. linear [Option ID = 29149]
3. elliptical [Option ID = 29151]
4. circular [Option ID = 29150]
Correct Answer :-
linear [Option ID = 29149]
Match the typical spectroscopic regions specified in Part-I with corresponding type of transitions
in Part-II and choose the correct answer from the following options.
Part-I Part-II
K. Infrared region 1. Electron transition involving valance electrons
L. Ultraviolet visible region 2. Nuclear transitions
M. X-ray region 3. Vibrational transitions of molecules
N. ?-ray region 4. Transitions involving inner shell electrons
[Question ID = 14775]
1. K->4 L->2 M->1 N->3 [Option ID = 29098]
2. K->3 L->4 M->1 N->2 [Option ID = 29100]
3. K->3 L->1 M->4 N->2 [Option ID = 29097]
4. K->1 L->2 M->3 N->4 [Option ID = 29099]
Correct Answer :-
K->3 L->1 M->4 N->2 [Option ID = 29097]
[Question ID = 14757]
1. [Option ID = 29027]
2. [Option ID = 29026]
3. [Option ID = 29025]
4. [Option ID = 29028]
Correct Answer :-
[Option ID = 29025]
[Question ID = 14755]
1. 3/5 [Option ID = 29018]
2. -5/2 [Option ID = 29017]
28)
29)
30)
31)
3. -5/3 [Option ID = 29020]
4. -2/5 [Option ID = 29019]
Correct Answer :-
-5/2 [Option ID = 29017]
[Question ID = 14756]
1. 1,0,2,3 [Option ID = 29021]
2. -1,1,0,3 [Option ID = 29024]
3. -1,1,0,2 [Option ID = 29023]
4. -2, -1, 1, 2 [Option ID = 29022]
Correct Answer :-
1,0,2,3 [Option ID = 29021]
[Question ID = 14747]
1. 20/3 [Option ID = 28987]
2. 40/3 [Option ID = 28986]
3. 0 [Option ID = 28988]
4. 4/3 [Option ID = 28985]
Correct Answer :-
4/3 [Option ID = 28985]
[Question ID = 14760]
1. 0.306 [Option ID = 29038]
2. 2.432 [Option ID = 29039]
3. 1.694 [Option ID = 29040]
4. 0.732 [Option ID = 29037]
Correct Answer :-
0.732 [Option ID = 29037]
32)
33)
34)
[Question ID = 14745]
1. [Option ID = 28979]
2. [Option ID = 28980]
3. [Option ID = 28977]
4. [Option ID = 28978]
Correct Answer :-
[Option ID = 28977]
[Question ID = 14751]
1. 1 [Option ID = 29004]
2. 1/4 [Option ID = 29002]
3. 1/12 [Option ID = 29001]
4. 0 [Option ID = 29003]
Correct Answer :-
1/12 [Option ID = 29001]
For an n-channel MOSFET with a gate oxide (?
r
= 3.9) thickness of 10 nm, V
th
= 0.6 V and W = 25
?m, L = 1 ?m and electron mobility in channel, ? = 200 cm
2
/V-s. The drain current at V
GS
= 5 V and
V
DS
= 0.1 V is
[Question ID = 14778]
1. 7.51 ? 10
-4
A [Option ID = 29111]
2. 3.05 ? 10
-5
A [Option ID = 29109]
3. 5.1 ? 10
-6
A [Option ID = 29110]
4. 8 ? 10
-5
A [Option ID = 29112]
Correct Answer :-
3.05 ? 10
-5
A [Option ID = 29109]
For z
6
+ z
3
+ 1 = 0 , the general solution is
[Question ID = 14744]
1. e
-4i?? /3
[Option ID = 28975]
35)
36)
37)
38)
2. e
-i?? /3
[Option ID = 28976]
3. e
i?? /3
[Option ID = 28974]
4. e
2i?? /3
[Option ID = 28973]
Correct Answer :-
e
2i?? /3
[Option ID = 28973]
A small concentration of minority carriers is injected into a homogeneous Semiconductor crystal
at one point. An electric field of 10 V/cm is applied across the crystal and this moves the minority
carriers by a distance of 1 cm in 20 ?sec. The mobility (in cm
2
/v-sec) of carriers is
[Question ID = 14768]
1. 5000 [Option ID = 29072]
2. 2000 [Option ID = 29069]
3. 4000 [Option ID = 29071]
4. 3000 [Option ID = 29070]
Correct Answer :-
2000 [Option ID = 29069]
Let the continuous random variable X denote the current measured in a thin copper wire in milli
amperes (mA). Assume that the range of X is 4.9 ? x ? 5.1 and f(x) = 5. The probability that a current
is less than 5mA is
[Question ID = 14748]
1. 0.4 [Option ID = 28990]
2. 0.2 [Option ID = 28992]
3. 0.5 [Option ID = 28989]
4. 0.3 [Option ID = 28991]
Correct Answer :-
0.5 [Option ID = 28989]
A transmission line has a characteristic impedance of 75 ? and a resistance of 5 ?/m. If the line
is distortion less, the attenuation constant (in Np/m) is
[Question ID = 14792]
1. 0.066 [Option ID = 29167]
2. 0.033 [Option ID = 29168]
3. 0.022 [Option ID = 29165]
4. 0.055 [Option ID = 29166]
Correct Answer :-
0.022 [Option ID = 29165]
A transmitting antenna with a 300 MHz carrier frequency produces 4 kW of power. If both
antennas has unity power gain, the power received by another antenna at a distance of 2 km is
[Question ID = 14791]
1. 8.44 mW [Option ID = 29161]
2. 4.4 ?W [Option ID = 29163]
3. 11.8 mW [Option ID = 29162]
39)
40)
41)
42)
4. 6.33 ?W [Option ID = 29164]
Correct Answer :-
8.44 mW [Option ID = 29161]
The power in power meter is displayed as -25 dB, when connected at the output of 30 dB
attenuator. The input power applied to this attenuator is
[Question ID = 14789]
1. 10.2 mW [Option ID = 29154]
2. 3.16 mW [Option ID = 29156]
3. 1.5 mW [Option ID = 29155]
4. 5 mW [Option ID = 29153]
Correct Answer :-
5 mW [Option ID = 29153]
The short-circuit current delivered by a 10 cm by 10 cm photocell (with 100% quantum
efficiency) illuminated by monochromatic light of 400 nm wavelength with a power density of 1000
W/m
2
is
[Question ID = 14773]
1. 6.85A [Option ID = 29092]
2. 5A [Option ID = 29089]
3. 8.32A [Option ID = 29091]
4. 3.2A [Option ID = 29090]
Correct Answer :-
5A [Option ID = 29089]
The recursion relation to solve x - e
-x
using Newton Raphson method is
[Question ID = 14758]
1. [Option ID = 29029]
2. [Option ID = 29030]
3. [Option ID = 29032]
4. [Option ID = 29031]
Correct Answer :-
[Option ID = 29029]
The temperature required to generate electron-hole pairs in silicon (E
g
= 1.1 eV) is (given
electron charge=1.6 ? 10
-19
J, Boltzman constant k =1.38 ? 10
-23
J/?K)
[Question ID = 14764]
43)
44)
45)
46)
1. 1522 K [Option ID = 29053]
2. 4174 K [Option ID = 29056]
3. 8502 K [Option ID = 29055]
4. 1130 K [Option ID = 29054]
Correct Answer :-
1522 K [Option ID = 29053]
The source of microwaves in a microwave oven is
[Question ID = 14786]
1. klystron [Option ID = 29141]
2. cyclotron [Option ID = 29144]
3. gyratron [Option ID = 29142]
4. magnetron [Option ID = 29143]
Correct Answer :-
klystron [Option ID = 29141]
The operating frequency of source in the microwave oven is
[Question ID = 14787]
1. 1.45 GHz [Option ID = 29146]
2. 4.45 GHz [Option ID = 29148]
3. 3.45 GHz [Option ID = 29145]
4. 2.45 GHz [Option ID = 29147]
Correct Answer :-
3.45 GHz [Option ID = 29145]
The line width of a He-Ne laser is 0.01 nm and the cross-sectional area of the beam is 0.01 cm
2
.
If the output power is 1mW, the radiation intensity per unit wavelength (in Watt/cm
3
) is
[Question ID = 14780]
1. 10
-8
[Option ID = 29118]
2. 10
10
[Option ID = 29117]
3. 10
8
[Option ID = 29119]
4. 10
-10
[Option ID = 29120]
Correct Answer :-
10
10
[Option ID = 29117]
The application of VSWR meter to measure
[Question ID = 14784]
1. air pressure [Option ID = 29136]
2. light intensity [Option ID = 29134]
3. SWR [Option ID = 29133]
4. scattering parameter [Option ID = 29135]
Correct Answer :-
SWR [Option ID = 29133]
FirstRanker.com - FirstRanker's Choice
1)
2)
3)
4)
DU PhD in Electronics
Topic:- DU_J19_PHD_ELEC
An electron beam with 3 eV energy strikes a crystal of cadmium sulfide (CdS) (bandgap E
g
=2.45
eV). Electrons scattered by the crystal move at a velocity of 4.4 ? 10
5
m/s. The scattered energy (in
eV) of the electrons is
[Question ID = 14763]
1. 0.55 eV [Option ID = 29050]
2. 1 eV [Option ID = 29049]
3. 1.45 eV [Option ID = 29051]
4. 0.05 eV [Option ID = 29052]
Correct Answer :-
1 eV [Option ID = 29049]
An ideal photodiode is made of a material with a bandgap energy of 2.35 eV. It operates at 300 K
and is illuminated by monochromatic light with wavelength of 400 nm. Its maximum efficiency is
[Question ID = 14772]
1. 80% [Option ID = 29088]
2. 25% [Option ID = 29085]
3. 75.7% [Option ID = 29086]
4. 48% [Option ID = 29087]
Correct Answer :-
25% [Option ID = 29085]
If line A of X-ray beam gives a first order reflection maxima at a glancing angle of 30? to the
smooth face of a crystal and line B of ? = 0.92 ? gives a third order reflection maxima at an angle 60?
from the face of same crystal, then the wavelength of line A is
[Question ID = 14769]
1. 3.36 ? [Option ID = 29073]
2. 6.72 ? [Option ID = 29076]
3. 0.84 ? [Option ID = 29075]
4. 1.59 ? [Option ID = 29074]
Correct Answer :-
3.36 ? [Option ID = 29073]
If ? = Kein? then the value of ?K? after normalization in the limits 0 to is
[Question ID = 15449]
5)
6)
7)
1. [Option ID = 31794]
2. [Option ID = 31793]
3. [Option ID = 31795]
4. [Option ID = 31796]
Correct Answer :-
[Option ID = 31793]
In a microwave test bench, a dip is shown on the CRO display by rotating the micrometer of
wavemeter, which indicates
[Question ID = 14785]
1. frequency of microwave signal is not same as frequency of wavemeter [Option ID = 29139]
2. frequency of microwave signal is zero [Option ID = 29137]
3. frequency of microwave signal is same as frequency of wavemeter [Option ID = 29138]
4. no signal propagates [Option ID = 29140]
Correct Answer :-
frequency of microwave signal is zero [Option ID = 29137]
In a p-type Si sample the hole concentration is 8 ? 10
15
/ cm
3
. The intrinsic carrier concentration
is 4 ? 10
10
/ cm
3
. The electron concentration is
[Question ID = 14766]
1. zero [Option ID = 29061]
2. 4 ? 10
10
/cm
3
[Option ID = 29062]
3. 1.5 ? 10
25
/cm
3
[Option ID = 29063]
4. 2 ? 10
5
/cm
3
[Option ID = 29064]
Correct Answer :-
zero [Option ID = 29061]
Sigma Electronics sells a microwave receiver (A) having an operating spot noise figure of 10 dB
when driven by a source with effective noise temperature 130 K. Deltalink (B) sells a receiver with a
standard spot noise figure of 6 dB when driven by a source with effective noise temperature 190 K.
Zebrotronics (C) sells a receiver with standard spot noise figure of 6 dB when driven by a source with
effective noise temperature 290 K. The best receiver to purchase is
[Question ID = 14782]
1. (A) [Option ID = 29125]
2. None [Option ID = 29128]
3. (C ) [Option ID = 29126]
4. (B) [Option ID = 29127]
Correct Answer :-
8)
9)
10)
11)
(A) [Option ID = 29125]
A silicon bar of 1?m long and 100 ?m
2
in cross-sectional area is doped with 10
17
cm
-3
Phosphorus.
The saturation velocity is 10
7
cm/sec. The current at 300 K with 10V applied is
[Question ID = 14762]
1. 0.16 A [Option ID = 29047]
2. 0.8 A [Option ID = 29048]
3. 0.5 A [Option ID = 29046]
4. 1.2 A [Option ID = 29045]
Correct Answer :-
1.2 A [Option ID = 29045]
A silicon PN junction diode under reverse bias has depletion region of width 20 ?m. Given, the
relative permittivity of silicon, ?
r
= 12.7 and the permittivity of free space ?
0
= 8.85 ? 10
-12
F/m. The
depletion capacitance of the diode per square meter is
[Question ID = 14767]
1. 7.65 ?F [Option ID = 29065]
2. 3 ?F [Option ID = 29067]
3. 8.15 ?F [Option ID = 29066]
4. 5.62 ?F [Option ID = 29068]
Correct Answer :-
7.65 ?F [Option ID = 29065]
A silica optical fiber with a core diameter large enough to be considered by ray theory analysis
has a core refractive index of 1.65 and a cladding refractive index of 1.52. The numerical aperture
(NA) of the fiber is
[Question ID = 14774]
1. 0.32 [Option ID = 29094]
2. 0.56 [Option ID = 29096]
3. 0.42 [Option ID = 29095]
4. 0.64 [Option ID = 29093]
Correct Answer :-
0.64 [Option ID = 29093]
A step-index fiber has numerical aperture (NA) of 0.16 and its core index (n
1
) = 1.45. If core
diameter = 0.6 cm and ? = 0.9 nm then normalized frequency of the fiber is _____
[Question ID = 14776]
1. 6.70 ? 10
3
Hz [Option ID = 29103]
2. 1.67 ? 10
3
Hz [Option ID = 29101]
3. 3.35 ? 10
3
Hz [Option ID = 29102]
4. 1.83 ? 10
3
Hz [Option ID = 29104]
Correct Answer :-
1.67 ? 10
3
Hz [Option ID = 29101]
12)
13)
14)
15)
A three level laser emits laser light near the centre of visible band. If E
2
- E
1
= 2.36 eV then the
wavelength of radiation is
[Question ID = 14777]
1. 550 nm [Option ID = 29105]
2. 670 nm [Option ID = 29107]
3. 620 nm [Option ID = 29108]
4. 450 nm [Option ID = 29106]
Correct Answer :-
550 nm [Option ID = 29105]
log(1 + x ) = _______________
[Question ID = 14750]
1. [Option ID = 28997]
2. [Option ID = 29000]
3. [Option ID = 28999]
4. [Option ID = 28998]
Correct Answer :-
[Option ID = 28997]
If the bandgap of GaAsP is 1.98 eV then the color of emitted light is
[Question ID = 14770]
1. Blue [Option ID = 29077]
2. Green [Option ID = 29078]
3. Yellow [Option ID = 29080]
4. Red [Option ID = 29079]
Correct Answer :-
Blue [Option ID = 29077]
A laser beam emerging from a laser tube operating at 800 nm has a cross-sectional diameter of 2
mm. The diameter of the beam at a distance of 1 km is approximately
[Question ID = 14779]
1. 10 cm [Option ID = 29116]
2. 10 mm [Option ID = 29113]
3. 80 cm [Option ID = 29114]
4. 8 cm [Option ID = 29115]
Correct Answer :-
10 mm [Option ID = 29113]
16)
17)
18)
19)
20)
A Si sample (n
i
= 1.5 ? 10
10
atoms/cm
3
) is doped with 10
17
As atoms/cm
3
. The position of E
f
related to E
i
is
[Question ID = 14761]
1. 0.895 eV [Option ID = 29043]
2. 0.407 eV [Option ID = 29044]
3. 0.532 eV [Option ID = 29042]
4. 0.217 eV [Option ID = 29041]
Correct Answer :-
0.217 eV [Option ID = 29041]
Attenuator reduces the microwave power in
[Question ID = 14783]
1. uni-direction [Option ID = 29130]
2. None of these [Option ID = 29132]
3. multi-direction [Option ID = 29131]
4. bi-direction [Option ID = 29129]
Correct Answer :-
bi-direction [Option ID = 29129]
A box contains 4 red balls and 6 black balls. Three balls are selected randomly from the box one
after another, without replacement. The probability that the selected set contains one red ball and
two black balls is
[Question ID = 14746]
1. 3/10 [Option ID = 28982]
2. 1/12 [Option ID = 28981]
3. 1/20 [Option ID = 28984]
4. 1/2 [Option ID = 28983]
Correct Answer :-
1/12 [Option ID = 28981]
Electron mobility in Si at room temperature (300 K) is 1400 cm
2
V
?1
s
?1
. The diffusion coefficient
of electrons is
[Question ID = 14765]
1. 36.22 cm
2
/s [Option ID = 29057]
2. 62.25 cm
2
/s [Option ID = 29059]
3. 32.76 cm
2
/s [Option ID = 29060]
4. 49.16 cm
2
/s [Option ID = 29058]
Correct Answer :-
36.22 cm
2
/s [Option ID = 29057]
In the Taylor series expansion of exp(x) + sin(x) about the point x = , the coefficient of (x -
)2 is
21)
22)
23)
24)
[Question ID = 15451]
1. 0.5 exp( ) [Option ID = 31802]
2. exp( ) [Option ID = 31801]
3. exp( ) - 1 [Option ID = 31804]
4. exp( ) + 1 [Option ID = 31803]
Correct Answer :-
exp( ) [Option ID = 31801]
In the expression 6 + 8i = 10e
i?
, the value of ? is,
[Question ID = 14743]
1. 85.16? [Option ID = 28971]
2. 53.13? [Option ID = 28972]
3. 36.16? [Option ID = 28970]
4. 13.13? [Option ID = 28969]
Correct Answer :-
13.13? [Option ID = 28969]
In the interval [0, ] the equation x = cos x
[Question ID = 15450]
1. exactly one solution [Option ID = 31799]
2. exactly two solutions [Option ID = 31797]
3. no solutions [Option ID = 31798]
4. an infinite number of solutions [Option ID = 31800]
Correct Answer :-
exactly two solutions [Option ID = 31797]
Choose the correct match out of the following options given below
Column I Column II
P. 2
nd
order DEs 1. Newton ? Raphson method
Q. Non-linear algebraic equations 2. Gauss Elimination
R. Linear algebraic equations 3. Simpson?s rule
S. Numerical integration 4. Runge-kutta method
[Question ID = 14754]
1. P->4 Q->1 R->2 S->3 [Option ID = 29014]
2. P->4 Q->2 R->3 S->1 [Option ID = 29015]
3. P->4 Q->2 R->1 S->3 [Option ID = 29016]
4. P->1 Q->2 R->3 S->4 [Option ID = 29013]
Correct Answer :-
P->1 Q->2 R->3 S->4 [Option ID = 29013]
Helical antenna has the following polarization
[Question ID = 14788]
25)
26)
27)
1. vertical [Option ID = 29152]
2. linear [Option ID = 29149]
3. elliptical [Option ID = 29151]
4. circular [Option ID = 29150]
Correct Answer :-
linear [Option ID = 29149]
Match the typical spectroscopic regions specified in Part-I with corresponding type of transitions
in Part-II and choose the correct answer from the following options.
Part-I Part-II
K. Infrared region 1. Electron transition involving valance electrons
L. Ultraviolet visible region 2. Nuclear transitions
M. X-ray region 3. Vibrational transitions of molecules
N. ?-ray region 4. Transitions involving inner shell electrons
[Question ID = 14775]
1. K->4 L->2 M->1 N->3 [Option ID = 29098]
2. K->3 L->4 M->1 N->2 [Option ID = 29100]
3. K->3 L->1 M->4 N->2 [Option ID = 29097]
4. K->1 L->2 M->3 N->4 [Option ID = 29099]
Correct Answer :-
K->3 L->1 M->4 N->2 [Option ID = 29097]
[Question ID = 14757]
1. [Option ID = 29027]
2. [Option ID = 29026]
3. [Option ID = 29025]
4. [Option ID = 29028]
Correct Answer :-
[Option ID = 29025]
[Question ID = 14755]
1. 3/5 [Option ID = 29018]
2. -5/2 [Option ID = 29017]
28)
29)
30)
31)
3. -5/3 [Option ID = 29020]
4. -2/5 [Option ID = 29019]
Correct Answer :-
-5/2 [Option ID = 29017]
[Question ID = 14756]
1. 1,0,2,3 [Option ID = 29021]
2. -1,1,0,3 [Option ID = 29024]
3. -1,1,0,2 [Option ID = 29023]
4. -2, -1, 1, 2 [Option ID = 29022]
Correct Answer :-
1,0,2,3 [Option ID = 29021]
[Question ID = 14747]
1. 20/3 [Option ID = 28987]
2. 40/3 [Option ID = 28986]
3. 0 [Option ID = 28988]
4. 4/3 [Option ID = 28985]
Correct Answer :-
4/3 [Option ID = 28985]
[Question ID = 14760]
1. 0.306 [Option ID = 29038]
2. 2.432 [Option ID = 29039]
3. 1.694 [Option ID = 29040]
4. 0.732 [Option ID = 29037]
Correct Answer :-
0.732 [Option ID = 29037]
32)
33)
34)
[Question ID = 14745]
1. [Option ID = 28979]
2. [Option ID = 28980]
3. [Option ID = 28977]
4. [Option ID = 28978]
Correct Answer :-
[Option ID = 28977]
[Question ID = 14751]
1. 1 [Option ID = 29004]
2. 1/4 [Option ID = 29002]
3. 1/12 [Option ID = 29001]
4. 0 [Option ID = 29003]
Correct Answer :-
1/12 [Option ID = 29001]
For an n-channel MOSFET with a gate oxide (?
r
= 3.9) thickness of 10 nm, V
th
= 0.6 V and W = 25
?m, L = 1 ?m and electron mobility in channel, ? = 200 cm
2
/V-s. The drain current at V
GS
= 5 V and
V
DS
= 0.1 V is
[Question ID = 14778]
1. 7.51 ? 10
-4
A [Option ID = 29111]
2. 3.05 ? 10
-5
A [Option ID = 29109]
3. 5.1 ? 10
-6
A [Option ID = 29110]
4. 8 ? 10
-5
A [Option ID = 29112]
Correct Answer :-
3.05 ? 10
-5
A [Option ID = 29109]
For z
6
+ z
3
+ 1 = 0 , the general solution is
[Question ID = 14744]
1. e
-4i?? /3
[Option ID = 28975]
35)
36)
37)
38)
2. e
-i?? /3
[Option ID = 28976]
3. e
i?? /3
[Option ID = 28974]
4. e
2i?? /3
[Option ID = 28973]
Correct Answer :-
e
2i?? /3
[Option ID = 28973]
A small concentration of minority carriers is injected into a homogeneous Semiconductor crystal
at one point. An electric field of 10 V/cm is applied across the crystal and this moves the minority
carriers by a distance of 1 cm in 20 ?sec. The mobility (in cm
2
/v-sec) of carriers is
[Question ID = 14768]
1. 5000 [Option ID = 29072]
2. 2000 [Option ID = 29069]
3. 4000 [Option ID = 29071]
4. 3000 [Option ID = 29070]
Correct Answer :-
2000 [Option ID = 29069]
Let the continuous random variable X denote the current measured in a thin copper wire in milli
amperes (mA). Assume that the range of X is 4.9 ? x ? 5.1 and f(x) = 5. The probability that a current
is less than 5mA is
[Question ID = 14748]
1. 0.4 [Option ID = 28990]
2. 0.2 [Option ID = 28992]
3. 0.5 [Option ID = 28989]
4. 0.3 [Option ID = 28991]
Correct Answer :-
0.5 [Option ID = 28989]
A transmission line has a characteristic impedance of 75 ? and a resistance of 5 ?/m. If the line
is distortion less, the attenuation constant (in Np/m) is
[Question ID = 14792]
1. 0.066 [Option ID = 29167]
2. 0.033 [Option ID = 29168]
3. 0.022 [Option ID = 29165]
4. 0.055 [Option ID = 29166]
Correct Answer :-
0.022 [Option ID = 29165]
A transmitting antenna with a 300 MHz carrier frequency produces 4 kW of power. If both
antennas has unity power gain, the power received by another antenna at a distance of 2 km is
[Question ID = 14791]
1. 8.44 mW [Option ID = 29161]
2. 4.4 ?W [Option ID = 29163]
3. 11.8 mW [Option ID = 29162]
39)
40)
41)
42)
4. 6.33 ?W [Option ID = 29164]
Correct Answer :-
8.44 mW [Option ID = 29161]
The power in power meter is displayed as -25 dB, when connected at the output of 30 dB
attenuator. The input power applied to this attenuator is
[Question ID = 14789]
1. 10.2 mW [Option ID = 29154]
2. 3.16 mW [Option ID = 29156]
3. 1.5 mW [Option ID = 29155]
4. 5 mW [Option ID = 29153]
Correct Answer :-
5 mW [Option ID = 29153]
The short-circuit current delivered by a 10 cm by 10 cm photocell (with 100% quantum
efficiency) illuminated by monochromatic light of 400 nm wavelength with a power density of 1000
W/m
2
is
[Question ID = 14773]
1. 6.85A [Option ID = 29092]
2. 5A [Option ID = 29089]
3. 8.32A [Option ID = 29091]
4. 3.2A [Option ID = 29090]
Correct Answer :-
5A [Option ID = 29089]
The recursion relation to solve x - e
-x
using Newton Raphson method is
[Question ID = 14758]
1. [Option ID = 29029]
2. [Option ID = 29030]
3. [Option ID = 29032]
4. [Option ID = 29031]
Correct Answer :-
[Option ID = 29029]
The temperature required to generate electron-hole pairs in silicon (E
g
= 1.1 eV) is (given
electron charge=1.6 ? 10
-19
J, Boltzman constant k =1.38 ? 10
-23
J/?K)
[Question ID = 14764]
43)
44)
45)
46)
1. 1522 K [Option ID = 29053]
2. 4174 K [Option ID = 29056]
3. 8502 K [Option ID = 29055]
4. 1130 K [Option ID = 29054]
Correct Answer :-
1522 K [Option ID = 29053]
The source of microwaves in a microwave oven is
[Question ID = 14786]
1. klystron [Option ID = 29141]
2. cyclotron [Option ID = 29144]
3. gyratron [Option ID = 29142]
4. magnetron [Option ID = 29143]
Correct Answer :-
klystron [Option ID = 29141]
The operating frequency of source in the microwave oven is
[Question ID = 14787]
1. 1.45 GHz [Option ID = 29146]
2. 4.45 GHz [Option ID = 29148]
3. 3.45 GHz [Option ID = 29145]
4. 2.45 GHz [Option ID = 29147]
Correct Answer :-
3.45 GHz [Option ID = 29145]
The line width of a He-Ne laser is 0.01 nm and the cross-sectional area of the beam is 0.01 cm
2
.
If the output power is 1mW, the radiation intensity per unit wavelength (in Watt/cm
3
) is
[Question ID = 14780]
1. 10
-8
[Option ID = 29118]
2. 10
10
[Option ID = 29117]
3. 10
8
[Option ID = 29119]
4. 10
-10
[Option ID = 29120]
Correct Answer :-
10
10
[Option ID = 29117]
The application of VSWR meter to measure
[Question ID = 14784]
1. air pressure [Option ID = 29136]
2. light intensity [Option ID = 29134]
3. SWR [Option ID = 29133]
4. scattering parameter [Option ID = 29135]
Correct Answer :-
SWR [Option ID = 29133]
47)
48)
49)
50)
The dependence of Doppler broadened line width of a laser transition on temperature, T is given
as
[Question ID = 14781]
1. T [Option ID = 29121]
2. T
2
[Option ID = 29124]
3. T
-1/2
[Option ID = 29122]
4. T
1/2
[Option ID = 29123]
Correct Answer :-
T [Option ID = 29121]
The return loss of a device is found to be 40 dB. The voltage standing wave ratio (VSWR) and
magnitude of reflection coefficient are respectively
[Question ID = 14790]
1. -1.02 and 0.1 [Option ID = 29158]
2. 1.02 and 0.01 [Option ID = 29159]
3. 2.44 and 0.02 [Option ID = 29160]
4. 0.81 and 0.1 [Option ID = 29157]
Correct Answer :-
0.81 and 0.1 [Option ID = 29157]
The de Broglie wavelength of an electron accelerated to a potential of 2kV is _______
[Question ID = 14771]
1. 3.46 ? 10
-11
m [Option ID = 29084]
2. 5.49 ? 10
-9
m [Option ID = 29083]
3. 1.73 ? 10
-11
m [Option ID = 29082]
4. 2.74 ? 10
-9
m [Option ID = 29081]
Correct Answer :-
2.74 ? 10
-9
m [Option ID = 29081]
The following equation needs to be numerically solved using the Newton-Raphson method x
3
+
4x - 9 = 0 . The iterative equation for this purpose is (k ? indicates the interation level)
[Question ID = 14753]
1. [Option ID = 29011]
2. [Option ID = 29012]
3. [Option ID = 29010]
4. [Option ID = 29009]
FirstRanker.com - FirstRanker's Choice
1)
2)
3)
4)
DU PhD in Electronics
Topic:- DU_J19_PHD_ELEC
An electron beam with 3 eV energy strikes a crystal of cadmium sulfide (CdS) (bandgap E
g
=2.45
eV). Electrons scattered by the crystal move at a velocity of 4.4 ? 10
5
m/s. The scattered energy (in
eV) of the electrons is
[Question ID = 14763]
1. 0.55 eV [Option ID = 29050]
2. 1 eV [Option ID = 29049]
3. 1.45 eV [Option ID = 29051]
4. 0.05 eV [Option ID = 29052]
Correct Answer :-
1 eV [Option ID = 29049]
An ideal photodiode is made of a material with a bandgap energy of 2.35 eV. It operates at 300 K
and is illuminated by monochromatic light with wavelength of 400 nm. Its maximum efficiency is
[Question ID = 14772]
1. 80% [Option ID = 29088]
2. 25% [Option ID = 29085]
3. 75.7% [Option ID = 29086]
4. 48% [Option ID = 29087]
Correct Answer :-
25% [Option ID = 29085]
If line A of X-ray beam gives a first order reflection maxima at a glancing angle of 30? to the
smooth face of a crystal and line B of ? = 0.92 ? gives a third order reflection maxima at an angle 60?
from the face of same crystal, then the wavelength of line A is
[Question ID = 14769]
1. 3.36 ? [Option ID = 29073]
2. 6.72 ? [Option ID = 29076]
3. 0.84 ? [Option ID = 29075]
4. 1.59 ? [Option ID = 29074]
Correct Answer :-
3.36 ? [Option ID = 29073]
If ? = Kein? then the value of ?K? after normalization in the limits 0 to is
[Question ID = 15449]
5)
6)
7)
1. [Option ID = 31794]
2. [Option ID = 31793]
3. [Option ID = 31795]
4. [Option ID = 31796]
Correct Answer :-
[Option ID = 31793]
In a microwave test bench, a dip is shown on the CRO display by rotating the micrometer of
wavemeter, which indicates
[Question ID = 14785]
1. frequency of microwave signal is not same as frequency of wavemeter [Option ID = 29139]
2. frequency of microwave signal is zero [Option ID = 29137]
3. frequency of microwave signal is same as frequency of wavemeter [Option ID = 29138]
4. no signal propagates [Option ID = 29140]
Correct Answer :-
frequency of microwave signal is zero [Option ID = 29137]
In a p-type Si sample the hole concentration is 8 ? 10
15
/ cm
3
. The intrinsic carrier concentration
is 4 ? 10
10
/ cm
3
. The electron concentration is
[Question ID = 14766]
1. zero [Option ID = 29061]
2. 4 ? 10
10
/cm
3
[Option ID = 29062]
3. 1.5 ? 10
25
/cm
3
[Option ID = 29063]
4. 2 ? 10
5
/cm
3
[Option ID = 29064]
Correct Answer :-
zero [Option ID = 29061]
Sigma Electronics sells a microwave receiver (A) having an operating spot noise figure of 10 dB
when driven by a source with effective noise temperature 130 K. Deltalink (B) sells a receiver with a
standard spot noise figure of 6 dB when driven by a source with effective noise temperature 190 K.
Zebrotronics (C) sells a receiver with standard spot noise figure of 6 dB when driven by a source with
effective noise temperature 290 K. The best receiver to purchase is
[Question ID = 14782]
1. (A) [Option ID = 29125]
2. None [Option ID = 29128]
3. (C ) [Option ID = 29126]
4. (B) [Option ID = 29127]
Correct Answer :-
8)
9)
10)
11)
(A) [Option ID = 29125]
A silicon bar of 1?m long and 100 ?m
2
in cross-sectional area is doped with 10
17
cm
-3
Phosphorus.
The saturation velocity is 10
7
cm/sec. The current at 300 K with 10V applied is
[Question ID = 14762]
1. 0.16 A [Option ID = 29047]
2. 0.8 A [Option ID = 29048]
3. 0.5 A [Option ID = 29046]
4. 1.2 A [Option ID = 29045]
Correct Answer :-
1.2 A [Option ID = 29045]
A silicon PN junction diode under reverse bias has depletion region of width 20 ?m. Given, the
relative permittivity of silicon, ?
r
= 12.7 and the permittivity of free space ?
0
= 8.85 ? 10
-12
F/m. The
depletion capacitance of the diode per square meter is
[Question ID = 14767]
1. 7.65 ?F [Option ID = 29065]
2. 3 ?F [Option ID = 29067]
3. 8.15 ?F [Option ID = 29066]
4. 5.62 ?F [Option ID = 29068]
Correct Answer :-
7.65 ?F [Option ID = 29065]
A silica optical fiber with a core diameter large enough to be considered by ray theory analysis
has a core refractive index of 1.65 and a cladding refractive index of 1.52. The numerical aperture
(NA) of the fiber is
[Question ID = 14774]
1. 0.32 [Option ID = 29094]
2. 0.56 [Option ID = 29096]
3. 0.42 [Option ID = 29095]
4. 0.64 [Option ID = 29093]
Correct Answer :-
0.64 [Option ID = 29093]
A step-index fiber has numerical aperture (NA) of 0.16 and its core index (n
1
) = 1.45. If core
diameter = 0.6 cm and ? = 0.9 nm then normalized frequency of the fiber is _____
[Question ID = 14776]
1. 6.70 ? 10
3
Hz [Option ID = 29103]
2. 1.67 ? 10
3
Hz [Option ID = 29101]
3. 3.35 ? 10
3
Hz [Option ID = 29102]
4. 1.83 ? 10
3
Hz [Option ID = 29104]
Correct Answer :-
1.67 ? 10
3
Hz [Option ID = 29101]
12)
13)
14)
15)
A three level laser emits laser light near the centre of visible band. If E
2
- E
1
= 2.36 eV then the
wavelength of radiation is
[Question ID = 14777]
1. 550 nm [Option ID = 29105]
2. 670 nm [Option ID = 29107]
3. 620 nm [Option ID = 29108]
4. 450 nm [Option ID = 29106]
Correct Answer :-
550 nm [Option ID = 29105]
log(1 + x ) = _______________
[Question ID = 14750]
1. [Option ID = 28997]
2. [Option ID = 29000]
3. [Option ID = 28999]
4. [Option ID = 28998]
Correct Answer :-
[Option ID = 28997]
If the bandgap of GaAsP is 1.98 eV then the color of emitted light is
[Question ID = 14770]
1. Blue [Option ID = 29077]
2. Green [Option ID = 29078]
3. Yellow [Option ID = 29080]
4. Red [Option ID = 29079]
Correct Answer :-
Blue [Option ID = 29077]
A laser beam emerging from a laser tube operating at 800 nm has a cross-sectional diameter of 2
mm. The diameter of the beam at a distance of 1 km is approximately
[Question ID = 14779]
1. 10 cm [Option ID = 29116]
2. 10 mm [Option ID = 29113]
3. 80 cm [Option ID = 29114]
4. 8 cm [Option ID = 29115]
Correct Answer :-
10 mm [Option ID = 29113]
16)
17)
18)
19)
20)
A Si sample (n
i
= 1.5 ? 10
10
atoms/cm
3
) is doped with 10
17
As atoms/cm
3
. The position of E
f
related to E
i
is
[Question ID = 14761]
1. 0.895 eV [Option ID = 29043]
2. 0.407 eV [Option ID = 29044]
3. 0.532 eV [Option ID = 29042]
4. 0.217 eV [Option ID = 29041]
Correct Answer :-
0.217 eV [Option ID = 29041]
Attenuator reduces the microwave power in
[Question ID = 14783]
1. uni-direction [Option ID = 29130]
2. None of these [Option ID = 29132]
3. multi-direction [Option ID = 29131]
4. bi-direction [Option ID = 29129]
Correct Answer :-
bi-direction [Option ID = 29129]
A box contains 4 red balls and 6 black balls. Three balls are selected randomly from the box one
after another, without replacement. The probability that the selected set contains one red ball and
two black balls is
[Question ID = 14746]
1. 3/10 [Option ID = 28982]
2. 1/12 [Option ID = 28981]
3. 1/20 [Option ID = 28984]
4. 1/2 [Option ID = 28983]
Correct Answer :-
1/12 [Option ID = 28981]
Electron mobility in Si at room temperature (300 K) is 1400 cm
2
V
?1
s
?1
. The diffusion coefficient
of electrons is
[Question ID = 14765]
1. 36.22 cm
2
/s [Option ID = 29057]
2. 62.25 cm
2
/s [Option ID = 29059]
3. 32.76 cm
2
/s [Option ID = 29060]
4. 49.16 cm
2
/s [Option ID = 29058]
Correct Answer :-
36.22 cm
2
/s [Option ID = 29057]
In the Taylor series expansion of exp(x) + sin(x) about the point x = , the coefficient of (x -
)2 is
21)
22)
23)
24)
[Question ID = 15451]
1. 0.5 exp( ) [Option ID = 31802]
2. exp( ) [Option ID = 31801]
3. exp( ) - 1 [Option ID = 31804]
4. exp( ) + 1 [Option ID = 31803]
Correct Answer :-
exp( ) [Option ID = 31801]
In the expression 6 + 8i = 10e
i?
, the value of ? is,
[Question ID = 14743]
1. 85.16? [Option ID = 28971]
2. 53.13? [Option ID = 28972]
3. 36.16? [Option ID = 28970]
4. 13.13? [Option ID = 28969]
Correct Answer :-
13.13? [Option ID = 28969]
In the interval [0, ] the equation x = cos x
[Question ID = 15450]
1. exactly one solution [Option ID = 31799]
2. exactly two solutions [Option ID = 31797]
3. no solutions [Option ID = 31798]
4. an infinite number of solutions [Option ID = 31800]
Correct Answer :-
exactly two solutions [Option ID = 31797]
Choose the correct match out of the following options given below
Column I Column II
P. 2
nd
order DEs 1. Newton ? Raphson method
Q. Non-linear algebraic equations 2. Gauss Elimination
R. Linear algebraic equations 3. Simpson?s rule
S. Numerical integration 4. Runge-kutta method
[Question ID = 14754]
1. P->4 Q->1 R->2 S->3 [Option ID = 29014]
2. P->4 Q->2 R->3 S->1 [Option ID = 29015]
3. P->4 Q->2 R->1 S->3 [Option ID = 29016]
4. P->1 Q->2 R->3 S->4 [Option ID = 29013]
Correct Answer :-
P->1 Q->2 R->3 S->4 [Option ID = 29013]
Helical antenna has the following polarization
[Question ID = 14788]
25)
26)
27)
1. vertical [Option ID = 29152]
2. linear [Option ID = 29149]
3. elliptical [Option ID = 29151]
4. circular [Option ID = 29150]
Correct Answer :-
linear [Option ID = 29149]
Match the typical spectroscopic regions specified in Part-I with corresponding type of transitions
in Part-II and choose the correct answer from the following options.
Part-I Part-II
K. Infrared region 1. Electron transition involving valance electrons
L. Ultraviolet visible region 2. Nuclear transitions
M. X-ray region 3. Vibrational transitions of molecules
N. ?-ray region 4. Transitions involving inner shell electrons
[Question ID = 14775]
1. K->4 L->2 M->1 N->3 [Option ID = 29098]
2. K->3 L->4 M->1 N->2 [Option ID = 29100]
3. K->3 L->1 M->4 N->2 [Option ID = 29097]
4. K->1 L->2 M->3 N->4 [Option ID = 29099]
Correct Answer :-
K->3 L->1 M->4 N->2 [Option ID = 29097]
[Question ID = 14757]
1. [Option ID = 29027]
2. [Option ID = 29026]
3. [Option ID = 29025]
4. [Option ID = 29028]
Correct Answer :-
[Option ID = 29025]
[Question ID = 14755]
1. 3/5 [Option ID = 29018]
2. -5/2 [Option ID = 29017]
28)
29)
30)
31)
3. -5/3 [Option ID = 29020]
4. -2/5 [Option ID = 29019]
Correct Answer :-
-5/2 [Option ID = 29017]
[Question ID = 14756]
1. 1,0,2,3 [Option ID = 29021]
2. -1,1,0,3 [Option ID = 29024]
3. -1,1,0,2 [Option ID = 29023]
4. -2, -1, 1, 2 [Option ID = 29022]
Correct Answer :-
1,0,2,3 [Option ID = 29021]
[Question ID = 14747]
1. 20/3 [Option ID = 28987]
2. 40/3 [Option ID = 28986]
3. 0 [Option ID = 28988]
4. 4/3 [Option ID = 28985]
Correct Answer :-
4/3 [Option ID = 28985]
[Question ID = 14760]
1. 0.306 [Option ID = 29038]
2. 2.432 [Option ID = 29039]
3. 1.694 [Option ID = 29040]
4. 0.732 [Option ID = 29037]
Correct Answer :-
0.732 [Option ID = 29037]
32)
33)
34)
[Question ID = 14745]
1. [Option ID = 28979]
2. [Option ID = 28980]
3. [Option ID = 28977]
4. [Option ID = 28978]
Correct Answer :-
[Option ID = 28977]
[Question ID = 14751]
1. 1 [Option ID = 29004]
2. 1/4 [Option ID = 29002]
3. 1/12 [Option ID = 29001]
4. 0 [Option ID = 29003]
Correct Answer :-
1/12 [Option ID = 29001]
For an n-channel MOSFET with a gate oxide (?
r
= 3.9) thickness of 10 nm, V
th
= 0.6 V and W = 25
?m, L = 1 ?m and electron mobility in channel, ? = 200 cm
2
/V-s. The drain current at V
GS
= 5 V and
V
DS
= 0.1 V is
[Question ID = 14778]
1. 7.51 ? 10
-4
A [Option ID = 29111]
2. 3.05 ? 10
-5
A [Option ID = 29109]
3. 5.1 ? 10
-6
A [Option ID = 29110]
4. 8 ? 10
-5
A [Option ID = 29112]
Correct Answer :-
3.05 ? 10
-5
A [Option ID = 29109]
For z
6
+ z
3
+ 1 = 0 , the general solution is
[Question ID = 14744]
1. e
-4i?? /3
[Option ID = 28975]
35)
36)
37)
38)
2. e
-i?? /3
[Option ID = 28976]
3. e
i?? /3
[Option ID = 28974]
4. e
2i?? /3
[Option ID = 28973]
Correct Answer :-
e
2i?? /3
[Option ID = 28973]
A small concentration of minority carriers is injected into a homogeneous Semiconductor crystal
at one point. An electric field of 10 V/cm is applied across the crystal and this moves the minority
carriers by a distance of 1 cm in 20 ?sec. The mobility (in cm
2
/v-sec) of carriers is
[Question ID = 14768]
1. 5000 [Option ID = 29072]
2. 2000 [Option ID = 29069]
3. 4000 [Option ID = 29071]
4. 3000 [Option ID = 29070]
Correct Answer :-
2000 [Option ID = 29069]
Let the continuous random variable X denote the current measured in a thin copper wire in milli
amperes (mA). Assume that the range of X is 4.9 ? x ? 5.1 and f(x) = 5. The probability that a current
is less than 5mA is
[Question ID = 14748]
1. 0.4 [Option ID = 28990]
2. 0.2 [Option ID = 28992]
3. 0.5 [Option ID = 28989]
4. 0.3 [Option ID = 28991]
Correct Answer :-
0.5 [Option ID = 28989]
A transmission line has a characteristic impedance of 75 ? and a resistance of 5 ?/m. If the line
is distortion less, the attenuation constant (in Np/m) is
[Question ID = 14792]
1. 0.066 [Option ID = 29167]
2. 0.033 [Option ID = 29168]
3. 0.022 [Option ID = 29165]
4. 0.055 [Option ID = 29166]
Correct Answer :-
0.022 [Option ID = 29165]
A transmitting antenna with a 300 MHz carrier frequency produces 4 kW of power. If both
antennas has unity power gain, the power received by another antenna at a distance of 2 km is
[Question ID = 14791]
1. 8.44 mW [Option ID = 29161]
2. 4.4 ?W [Option ID = 29163]
3. 11.8 mW [Option ID = 29162]
39)
40)
41)
42)
4. 6.33 ?W [Option ID = 29164]
Correct Answer :-
8.44 mW [Option ID = 29161]
The power in power meter is displayed as -25 dB, when connected at the output of 30 dB
attenuator. The input power applied to this attenuator is
[Question ID = 14789]
1. 10.2 mW [Option ID = 29154]
2. 3.16 mW [Option ID = 29156]
3. 1.5 mW [Option ID = 29155]
4. 5 mW [Option ID = 29153]
Correct Answer :-
5 mW [Option ID = 29153]
The short-circuit current delivered by a 10 cm by 10 cm photocell (with 100% quantum
efficiency) illuminated by monochromatic light of 400 nm wavelength with a power density of 1000
W/m
2
is
[Question ID = 14773]
1. 6.85A [Option ID = 29092]
2. 5A [Option ID = 29089]
3. 8.32A [Option ID = 29091]
4. 3.2A [Option ID = 29090]
Correct Answer :-
5A [Option ID = 29089]
The recursion relation to solve x - e
-x
using Newton Raphson method is
[Question ID = 14758]
1. [Option ID = 29029]
2. [Option ID = 29030]
3. [Option ID = 29032]
4. [Option ID = 29031]
Correct Answer :-
[Option ID = 29029]
The temperature required to generate electron-hole pairs in silicon (E
g
= 1.1 eV) is (given
electron charge=1.6 ? 10
-19
J, Boltzman constant k =1.38 ? 10
-23
J/?K)
[Question ID = 14764]
43)
44)
45)
46)
1. 1522 K [Option ID = 29053]
2. 4174 K [Option ID = 29056]
3. 8502 K [Option ID = 29055]
4. 1130 K [Option ID = 29054]
Correct Answer :-
1522 K [Option ID = 29053]
The source of microwaves in a microwave oven is
[Question ID = 14786]
1. klystron [Option ID = 29141]
2. cyclotron [Option ID = 29144]
3. gyratron [Option ID = 29142]
4. magnetron [Option ID = 29143]
Correct Answer :-
klystron [Option ID = 29141]
The operating frequency of source in the microwave oven is
[Question ID = 14787]
1. 1.45 GHz [Option ID = 29146]
2. 4.45 GHz [Option ID = 29148]
3. 3.45 GHz [Option ID = 29145]
4. 2.45 GHz [Option ID = 29147]
Correct Answer :-
3.45 GHz [Option ID = 29145]
The line width of a He-Ne laser is 0.01 nm and the cross-sectional area of the beam is 0.01 cm
2
.
If the output power is 1mW, the radiation intensity per unit wavelength (in Watt/cm
3
) is
[Question ID = 14780]
1. 10
-8
[Option ID = 29118]
2. 10
10
[Option ID = 29117]
3. 10
8
[Option ID = 29119]
4. 10
-10
[Option ID = 29120]
Correct Answer :-
10
10
[Option ID = 29117]
The application of VSWR meter to measure
[Question ID = 14784]
1. air pressure [Option ID = 29136]
2. light intensity [Option ID = 29134]
3. SWR [Option ID = 29133]
4. scattering parameter [Option ID = 29135]
Correct Answer :-
SWR [Option ID = 29133]
47)
48)
49)
50)
The dependence of Doppler broadened line width of a laser transition on temperature, T is given
as
[Question ID = 14781]
1. T [Option ID = 29121]
2. T
2
[Option ID = 29124]
3. T
-1/2
[Option ID = 29122]
4. T
1/2
[Option ID = 29123]
Correct Answer :-
T [Option ID = 29121]
The return loss of a device is found to be 40 dB. The voltage standing wave ratio (VSWR) and
magnitude of reflection coefficient are respectively
[Question ID = 14790]
1. -1.02 and 0.1 [Option ID = 29158]
2. 1.02 and 0.01 [Option ID = 29159]
3. 2.44 and 0.02 [Option ID = 29160]
4. 0.81 and 0.1 [Option ID = 29157]
Correct Answer :-
0.81 and 0.1 [Option ID = 29157]
The de Broglie wavelength of an electron accelerated to a potential of 2kV is _______
[Question ID = 14771]
1. 3.46 ? 10
-11
m [Option ID = 29084]
2. 5.49 ? 10
-9
m [Option ID = 29083]
3. 1.73 ? 10
-11
m [Option ID = 29082]
4. 2.74 ? 10
-9
m [Option ID = 29081]
Correct Answer :-
2.74 ? 10
-9
m [Option ID = 29081]
The following equation needs to be numerically solved using the Newton-Raphson method x
3
+
4x - 9 = 0 . The iterative equation for this purpose is (k ? indicates the interation level)
[Question ID = 14753]
1. [Option ID = 29011]
2. [Option ID = 29012]
3. [Option ID = 29010]
4. [Option ID = 29009]
Correct Answer :-
[Option ID = 29009]
FirstRanker.com - FirstRanker's Choice
This post was last modified on 19 June 2020