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]

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1)

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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 :-

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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

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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

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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]

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This post was last modified on 19 June 2020