Engineering Assistant/Overseer Gr I (Electronics) Answer Key

Question 1

A semiconductor has _______ valence electrons.

A

2

B

3

C

4

D

5

Question 2

In a ______ the energy gap between the conduction band and valence band of a substance is of the order of 0.7 eV

A

conductor

B

semiconductor

C

insulator

D

none of the above

Question 3

In a Zener regulator, change in load current produces change in _______

A

Zener current

B

Zener voltage

C

A & B

D

None of the above

Question 4

Maximum efficiency of a half wave rectifier is ______

A

50%

B

25%

C

40.6%

D

81.2%

Question 5

A center tap full wave rectifier consists of _______ diodes.

A

1

B

2

C

3

D

4

Question 6

What is the type of filter shown in the figure?

A

Low pass filter

B

High pass filter

C

Band pass filter

D

Band reject filter

Question 7

In a transistor there are ______ depletion layers.

A

1

B

2

C

3

D

4

Question 8

If the value of α in a transistor is 0.9, then value of b is ______

A

9

B

10

C

90

D

100

Question 9

Where should be the bias point set in order to make transistor work as an amplifier?

A

active

B

cutoff

C

saturation

D

none of the above

Question 10

Emitter follower is used for ______

A

current gain

B

voltage gain

C

impedance matching

D

none of the above

Question 11

Which among the following does not belong to the category of LC oscillators?

A

Hartley oscillator

B

Colpitts oscillator

C

crystal oscillator

D

none of the above

Question 12

The channel of a JFET is between the ______

A

input and output

B

gate and drain

C

gate and source

D

drain and source

Question 13

Choose the correct statement

A

MOSFET is a unipolar, voltage controlled, two terminal device

B

MOSFET is a bipolar, current controlled, two terminal device

C

MOSFET is a unipolar, voltage controlled, three terminal device

D

MOSFET is a bipolar, current controlled, three terminal device

Question 14

What are the working regions of a unijunction transistor?

A

Negative Resistance region

B

Saturation region

C

Linear region

D

Cutoff region

Question 15

Which of the following is/are optoelectronic devices?

A

photodiodes

B

light emitting diodes

C

solar cells

D

all of the above

Question 16

An optocoupler provides _______ between input and output

A

induction

B

amplification

C

isolation

D

oscillation

Question 17

Clamping is the process of introducing a/an ______

A

dc level to a dc signal

B

dc level to an ac signal

C

ac level to a dc signal

D

ac level to an ac signal

Question 18

A square wave oscillator is a/an ______ multivibrator.

A

astable

B

monostable

C

bistable

D

none of the above

Question 19

The Op-amp can amplify ______

A

dc signals only

B

ac signals only

C

both dc and ac signals

D

none of the above

Question 20

The common-mode voltage gain of an Op-amp is _______

A

equal to differential voltage gain

B

smaller than differential voltage gain

C

greater than differential voltage gain

D

none of the above

Question 21

What is the feedback factor of voltage follower circuit?

A

zero

B

unity

C

between zero and one

D

infinity

Question 22

The internal circuitry of the 555 timer consists of _____, an R-S flip-flop, a transistor switch, an output buffer amplifier, and a voltage divider.

A

a peak detector

B

a comparator

C

a voltage amplifier

D

two comparators

Question 23

The 7912 regulator IC provides _______

A

5v

B

–5v

C

12v

D

–12v

Question 24

The fastest A/D converter is _______ ADC

A

single slope ramp comparator

B

dual slope integrator

C

successive approximation

D

counter type

Question 25

What is the disadvantage of binary weighted type DAC?

A

slow switching

B

requires wide range of resistors

C

high operationg frequency

D

high power consumption

Question 26

The phase velocity of a waveguide at cutoff frequency is

A

Zero

B

Finite

C

Infinite

D

One

Question 27

For a short circuited loss-less line having length less than a quarter wavelength will have input impedance

A

Purely Inductive

B

Purely resistive

C

Resonative

D

Purely capacitive

Question 28

The main reason for occurring of standing waves is due to

A

Dispersion

B

Impedance mismatch

C

Reflection

D

Transmission mode

Question 29

The speakers which cover the frequencies from 16Hz to 1000Hz are called

A

Squawkers

B

Tweeters

C

Baffle

D

Woofers

Question 30

The ratio of the current or voltage entering the network to the current or voltage leaving the network is known as

A

Characteristic Impedance

B

Propagation Constant

C

Iterative Impedance

D

Image Impedance

Question 31

A number of identical parallel antennas arranged along a line perpendicular to the line of array axis and each element fed with current of equal magnitude and same phase is known as

A

Broad side array

B

Log periodic array

C

End fire array

D

Collinear array

Question 32

RF amplifier in a super heterodyne receiver is used to

A

increase tracking

B

increase adjacent-channel rejection

C

increase the tuning range

D

increase rejection of the image frequency

Question 33

In TV circuits the equalizing pulses are sent during

A

horizontal blanking

B

horizontal retrace

C

vertical retrace

D

vertical blanking

Question 34

Frequencies in the UHF range are normally propagated by

A

space waves

B

sky waves

C

surface waves

D

ground waves

Question 35

An example for multiband HF receiving antenna is

A

conical horn

B

folded dipole

C

rhombic loop

D

log periodic

Question 36

A PIN diode is

A

a semiconductor point-contact diode

B

used as a microwave switch

C

often used as a microwave detector

D

a microwave mixer diode

Question 37

The modulation system which is commonly used in telegraphic communication is

A

pulse-code modulation

B

two-tone modulation

C

frequency-shift keying

D

single-tone modulation

Question 38

The code which is used for parity checks is

A

Gray

B

ASCII

C

EBCDIC

D

Baudot

Question 39

The transmission rate of data in a modem is measured in

A

bytes per second

B

Gigahertz

C

bits per second

D

word per minute

Question 40

The On-Off keying method of data transmission is otherwise known as

A

ASK

B

FSK

C

PSK

D

BPSK

Question 41

The type of microphone used in telephone is

A

Condenser microphone

B

Ribbon microphone

C

Peizo electric

D

Carbon microphone

Question 42

The type of noise which is having greater impact at high frequencies is

A

random noise

B

Johnson noise

C

transit-time noise

D

shot noise

Question 43

Which of the following modulation system is the most noise resistant one?

A

PWM

B

Delta

C

PCM

D

Differential PCM

Question 44

The reason for Rayleigh scattering loss in optical fibre is

A

bending of fibre

B

structural fault in glass

C

impurities present

D

due to dispersion

Question 45

Quantizing noise occurs in

A

amplitude modulation

B

frequency modulation

C

pulse-code modulation

D

pulse-width modulation

Question 46

The main disadvantage of CW Doppler radar is

A

does not give target range

B

does not give target position

C

does not give target velocity

D

does not give angular position of target

Question 47

The circuit that separates sync pulses from the composite video waveform is

A

Schmitt trigger

B

a clipper

C

an integrator

D

a differentiator

Question 48

Optical fibres used for communication purpose are mostly fabricated using

A

Silica

B

Plastic

C

Ceramics

D

Copper

Question 49

Which of the following expression is true in the case of open circuit parameters?

A

V₁ = Z₁₁ V₁ + Z₁₂ I₂

B

V₁ = Z₁₁ I₁ + Z₁₂ V₂

C

V₁ = Z₁₁ I₁ + Z₁₂ I₂

D

V2 = Z₁₁ I₁ + Z₁₂ I₂

Question 50

The A scope displays

A

target position and range

B

the target velocity

C

the target position

D

the target range only

Question 51

According to Kepler"s law, the orbit of any smaller body about a larger body is always _______

A

Circular

B

Polar

C

Ellipse

D

Inclined

Question 52

Perigee is

A

the point on the satellite orbit farthest from the centre of earth

B

the point on the satellite orbit nearest to the centre of earth

C

the point on the earth that is farthest from the centre of satellite orbit

D

the point on the earth nearest to the centre of satellite orbit

Question 53

The inclination of a retrograde orbit lies between

A

0° and 90°

B

90° and 180°

C

180° and 270°

D

270° and 360°

Question 54

Geosynchronous orbit is at a distance of _______ above the surface of the earth

A

5000 KM

B

46756 KM

C

34000 KM

D

35786 KM

Question 55

The project Iridium is the most important application of

A

LEO satellites

B

MEO satellites

C

GEO satellites

D

HEO satellites

Question 56

"The apogee and perigee are always exactly opposite to each other" – the statement is

A

True

B

False

C

Partially True

D

Irrelevant

Question 57

The basic cassegrain antenna consists of

A

a main paraboloid and a sub reflector, which is an ellipsoid

B

a main paraboloidal reflector

C

a main paraboloid and a sub reflector which is hyperboloid

D

a main hyperboloid and a sub reflector which is paraboloid

Question 58

Denoting the focal distance of a parabolic reflector by "p" and focal length "f" then the Space Attenuation Function (SAF) is given by

A

p/f

B

(p/f)^2

C

f/p

D

(f/p)^2

Question 59

Satellites known as "spinners" are used for

A

Spin control

B

Attitude control

C

Power control

D

Orbit control

Question 60

Station keeping is applicable for

A

Orbit control of Geostationary satellites

B

Attitude control of Geostationary satellites

C

Power control of Geostationary satellites

D

Thermal control of Geostationary satellites

Question 61

The system which allows the antenna to handle transmit or receive signals simultaneously is known as

A

Diplexer

B

Duplexer

C

Combiner

D

Divider

Question 62

Which was the first communication satellite placed in the Geostationary orbit?

A

MSAT

B

INSAT I

C

VSAT

D

INTELSAT I

Question 63

The series of interconnected units which forms a single communication channel between transmit and receive antennas in a communication satellite is known as

A

Transceivers

B

Demultiplexers

C

Transponders

D

Duplexers

Question 64

The TV system employs a single outdoor unit so that all channels are made available simultaneously at the indoor receiver is named as

A

MA TV

B

DBS TV

C

FM TV

D

CA TV

Question 65

The ascending nodes of orbits in the GPS constellation are separated by ______ and the inclination of each orbit is ______

A

70°, 65°

B

60°, 55°

C

50°, 45°

D

40°, 35°

Question 66

"The passive satellite cannot generate power of its own and it reflects the incident power"; the statement is

A

True

B

False

C

Partially True

D

Irrelevant

Question 67

Which co-ordinate system is used with GPS system?

A

Geosynchronous-equatorial co-ordinate system

B

Earthcentric-equatorial co-ordinate system

C

Geocentric-equatorial coordinate system

D

Both (B) & (C)

Question 68

The effects of eclipse does not affect the operation of Geostationary satellite, if the satellite longitudes are _______ of earth station.

A

North East

B

North West

C

East

D

West

Question 69

Solar panels in satellites are arranged in the form of ______ to obtain high power.

A

rectangular arrays

B

cylindrical arrays

C

rectangular solar sails

D

cylindrical solar sails

Question 70

The system which transmits information about the satellite to earth station and receives command signals from the earth station is known as

A

Transponder

B

TT & C

C

Transceiver

D

LNA

Question 71

The temperature extremes experienced from solar flux and cold background of deep space can be minimized by

A

Spinning satellites

B

Body stabilized satellites

C

Both (A) & (B)

D

None of the above

Question 72

"Space Transportation System (STS) is an expendable launch vehicle" – the statement is

A

True

B

False

C

Irrelevant

D

None of these

Question 73

Which band of frequencies are used for the satellite services in MSAT?

A

C-band

B

Ka-band

C

Ku-band

D

L-band

Question 74

In C-band, the nominal up link and downlink frequencies are

A

8GHz and 6GHz

B

12GHz and 4GHz

C

6GHz and 4GHz

D

12GHz and 6GHz

Question 75

The conditions required for an orbit to be geostationary

A

the orbit must be elliptical

B

the orbit must be circular

C

the orbit must be polar

D

the orbit must be inclined

Question 76

First version of GSM used

A

64 full duplex channels

B

124 full duplex channels

C

64 half duplex channels

D

124 half duplex channels

Question 77

The minimum distance which allows the same frequency to be reused will depend on

A

Number of co-channel cells in the vicinity of center cell

B

The type of geographic terrain

C

The antenna height and transmitted power at each cell site

D

All of the above

Question 78

Transmission power of a cell has to be limited in order to

A

Achieve higher capacity

B

Avoid interference with the next cell using the same frequency

C

Avoid multipath propagation

D

None of the above

Question 79

The time over which a call is made within a cell without handoff is called ______

A

delay time

B

dwell time

C

seek time

D

guard time

Question 80

In fast fading

A

Coherence time is greater than symbol period

B

Coherence time is lesser than symbol period

C

Coherence time is equal to symbol period

D

Coherence time is independent of symbol period

Question 81

In FDM, frequency band overlapping is avoided using

A

Guard band

B

Framing band

C

Synchronizing pulses

D

None of the above

Question 82

In a cell, which is the radio channel used for transmission of call setup, call request and call initiation _______?

A

Forward channel

B

Control channel

C

Uplink channel

D

Reverse channel

Question 83

The handoff operation involves

A

Identifying the MSC and the call will be connected to the MSC

B

Identifies the voice channel to instruct the mobile telephone to ring

C

Identifying a new base station and reallocating the channels with the new base station.

D

Instructs the base station to move the call to an unused voice channel within the cell

Question 84

Code Division multiple access scheme is based on

A

QPSK

B

BPSK

C

Spread spectrum technology

D

BFSK

Question 85

Delay spread is due to

A

Multipath reflection

B

Frequency dispersion

C

Fresnel zone

D

Doppler effect

Question 86

Which of the following is true in a DECT system?

A

The range is limited to about 300m from base station

B

Can handle handover, but it is not designed to work at high speed

C

Works at a frequency range of 1880-1990 MHz

D

All of the above

Question 87

The channel capacity may be improved by using

A

Cell splitting

B

Hand off

C

Frequency hopping

D

Channel spacing

Question 88

If bandwidth over which the channel has constant gain and linear phase response is smaller than the bandwidth of the transmitted signal, the received signal undergoes _______

A

Flat fading

B

Rayleigh fading

C

Frequency selective fading

D

Slow fading

Question 89

_______ is a dynamic database which stores all important information needed for users currently associated to the MSC.

A

ISDN

B

VLR

C

HLR

D

EIR

Question 90

In mobile communication, the commonly used shape of a cell is hexagon because

A

Fewer number of cells are required

B

Provides maximum processing density than any other geometrical shape

C

It leaves no uncovered area

D

All of the above

Question 91

Which of the following multiple access scheme is using soft handover?

A

FDMA

B

TDMA

C

SDMA

D

CDMA

Question 92

The operation subsystem of GSM has OMC, AuC and EIR. Here EIR stands for

A

Enhanced identity register

B

Equipment identity register

C

Electronic identity register

D

Equipment inbuilt register

Question 93

Crosstalk from two different radio transmitters using the same channel may result in _______.

A

Adjacent channel interference

B

Multiple access interference

C

Co-channel interference

D

Self-interference

Question 94

______ resolves the problem of limited radio spectrum.

A

handover

B

cell splitting

C

frequency hopping

D

MAC

Question 95

The statistical measure of the range of frequency over which the channel can be considered flat is known as _______

A

Coherence time

B

Transmission bandwidth

C

Coherence bandwidth

D

Propagation time

Question 96

In a GSM system identify the function of MSC.

A

Takes care of handoff from one BTS to the other

B

Stores dynamic information while logged onto GSM

C

Co-ordinates all the activities of base station and connects the entire cellular system to PSTN.

D

All of the above

Question 97

In GSM _____ is used to separate uplink and downlink

A

TDM

B

FDD

C

TDD

D

FDM

Question 98

Suppose there are N cells in a cellular system and each cell is allocated K channel the total number of available channel is given by

A

S = N + K

B

S = K/N

C

S = N/K

D

S – K * N

Question 99

Before a subscriber can use any service from GSM network, he must be authenticated. This authentication is based on _______

A

ISDN

B

SIM

C

DTMF

D

BTS

Question 100

Near-far effect is a severe problem in wireless networks using ______

A

TDMA

B

FDMA

C

SDMA

D

CDMA

137/2021 - Engineering Assistant/Overseer Gr I (Electronics)