Font size
Worksheetsfundcom/electronics/eelectrical equipment
Total questions: 111
Worksheet time: 56mins
Which of the following characteristics of a sine wave can be modulated?
amplitude
angular phase
angular velocity
all of these
The following are advantages of modulation except
allow the use of practical-size antenna
separate differing transmission
circuit simplicity
overcomes difficulty in transmission at low frequencies
Amplitude modulation generated at a very low voltage or power amplifier is
modulation.
minimum
collector
high-level
low-level
In AM, carrier amplitude variation depends on modulating signal's
amplitude
frequency
amplitude and frequency
none of these
A 400 watts carrier is modulated to a depth of 75 percent. Calculate the total power in the modulated wave.
512.5 W
500 W
530 W
515.5 W
If the receive signal is 600 kHz in an AM broadcast, what is the local oscillator frequency?
600 kHz
145 kHz
1055 kHz
455 kHz
The instantaneous voltage of modulated FM carrier is given by v = 10 sin (750x10 t + 10 sin 1000t). The carrier frequency is
750 MHz
1000 MHz
119.37 MHz
1000 Hz
The amount of frequency deviation from the carrier center of frequency in an FM transmitter
is proportional to the
shape
amplitude
frequency
phase
What is the common unit of the sound absorption coefficient?
watt
erg
sabine
decibel
The input is 0.1 W and the network gain is 13 dB, the output is
2.0 W
2.5 W
1.5 W
1.8 W
Tendency of sound energy to spread
Reflection
Diffraction
Rarefaction
Refraction
One octave above 600 Hz is
601 Hz
800 Hz
1400 Hz
1200 Hz
A technique that enables more than one data source to share the use of a common facility
companding
multiplexing
sharing
all of these
Which of the following carries the most number of channels?
50 multiplexer
100 pairs of cables
100 chips
1 fiber optic
What is the optical source for the transmitting end of an optic fiber cable?
Halogen
LED
Injection Laser Diode
Photocell
What is the most commonly used fiber optic cable?
single mode step index
single mode graded index
Multi mode step index
Multi mode graded index
Which type of fiber optic cable is best for very high speed data?
Single mode step index
Multimode graded index
Single mode graded index
Multimode step index
What replaces coaxial cable for terrestrial transmission?
copper cable
point to point wireless transmission
aluminum cable
fiber optics
The core of a fiber optic cable is made of
Air
Glass
Diamonds
Quartz
A type of communication that uses light rather than electricity to communicate is
called
Laser carrier
Microwave
Powerline carrier
Fiber optic
Which of the following
principle will the operation of fiber-optic cable is based?
dispersion
refraction
reflection
absorption
A transponder with a bandwidth of 400 MHz uses polarization diversity. If the wavelength allocated to transmit a single telephone channel is 4 kHz, how many telephone channels can be carried by the transponder?
300,000
200,000
400,000
100,000
The master control center for a cellular telephone system is the
cell site
mobile telephone switching office
central office
branch office
What contains in each cell site of cellular telephone system?
repeater
touch tone processor
direct-link to branch
control computer
What is the maximum output power of a cellular transmitter?
60 watts
3 watts
6 watts
30 watts
s a cellphone user passes from one cell to another:
A "handoff" process occurs
A "sectoring" process occurs
both cells will handle the cell
nothing occurs
In which type of electronic communications does the information travel in two directions?
half duplex
full duplex
multiplex
bicomm
A type of electronics communication in which only one party transmits at a time.
Full duplex
Half duplex
Bicom
Simplex
A "repeater" is used to:
send a message multiple times over a channel
send a message over multiple channels at the same time
extend the range of a radio communications system
cancel the effects of fading
Single-Side Band signal produces a peak to peak voltage of 720 V on voice peaks across a 75-ohm antenna. What is the peak envelope power?
865 W
856 W
835 W
853 W
In 1885, who invented antenna for long distance transmission of electromagnetic waves?
Benjamin Franklin
Guglielmo Marconi
Isaac Newton
Carl Siemen
An antenna that transmits and receives equally well in all direction is said to be
Omnidirectional
Bidirectonal
Unidirectional
Quasidirectional
Radiated power unit area
Air density
Sound density
Power density
Signal density
It refers to a device that merely boosts a signal and passes it on.
amplifier
booster
op-amp
repeater
A collision avoidance radar is designed to detect the presence of vehicles up to a range of 0.50 km. What is the maximum pulse repetition frequency, PRF?
600 kHz
300 MHz
300 kHz
600 MHz
The electron is a/an _________charged particle of electricity
neutral
negatively
positively
zero
Which has the least number of valence electrons?
conductor
elemental semiconductor
insulator
compound semiconductor
A semiconductor that is free from impurities.
intrinsic semiconductor
compensated semiconductor
extrinsic semiconductor
elemental semiconductor
Which of the following defined the Fermi energy?
The amount of energy which a valence electron can have at room temperature.
The amount of energy which a hole can have at room temperature.
The amount of energy which must be given to an electron to move it to conductor band.
The amount of energy which must be given to hole it in valence band.
P-type semiconductor has an excess of
electron
hole
proton
neutron
The depletion region of a junction diode forms the
Plates
Dielectric
Package
none of these
A semiconductor frequently used to rectify AC current to DC is called
zinc oxide
transistor
tube
diode
he resistor is connected across an AC supply of 220 V. The power drawn is 1000 W. If a diode were connected in series with the resistor, what would be the power absorbed by the resistor?
850 W
250 W
200 W
500 W
A circuit consists of a resistor which is connected in series with a perfect diode. When connected across a 20 V battery, then current measured 10 A. However, when connected across a 30 V battery but with a reverse polarity, what would be the new current?
15 A
zero current
20 A
None of these
In order to measure the voltage signals from a filtered rectifier circuit, DC and AC voltmeters were used. The readings were 30 V DC and 2.5 V rms respectively. Determine the ripple of the output voltage.
9%
8.33%
7%
7.33%
An ideal full wave rectifier with a non-inductive load has zero transformation losses. What is the efficiency?
100
90
80
70
An unregulated power supply which consists of a transformer, a rectifier and a filter has some characteristics which are as follows EXCEPT one. Which one is this?
It has good voltage regulation.
It is relatively expensive.
The output voltage varies with the load.
The output voltage depends on the input voltage.
The resistance of a semiconductor is known as
bulk resistance
intrinsic resistance
extrinsic resistance
dynamic resistance
Half wave rectifiers has a maximum efficiency of
40.6%
78.5%
81.2%
50%
Diode circuit that is used to cut a portion of the input signal.
clipper
clamper
peak detector
level shifter
Ripple factor of a full wave rectifier.
0.24
2.42
1.21
0.48
The output of a full wave rectifier with an input frequency of 60 Hz.
60 Hz
100 Hz
120 Hz
200 Hz
Zener diode normally requires
forward
reverse
maximum
impedance
What is one important thing that transistors do?
amplify weak signals
rectify line voltage
emit sound
emit light
An advantage of a transistor is
small size
lack of heater
It lasts indefinitely
all of these
A transistor has a collector current of 2 mA. If the current gain is gain 135, what is the base current?
14.8 μA
15.8 μA
16.8 μA
17.8 μA
The reason, why a metal tab of a power transistor is fasten to the chassis of an electronic equipment is
to hold the transistor firmly
for aesthetic value purposes
for heat to escape easily
to contribute to the rigidity of the equipment
It is a very powerful small component of a computer. Which one?
diode
triode
chip
internet
What is the equivalent of the collector terminal of transistor in FET?
grid
gate
source
drain
A prototransistor can be used for
high isolation
lighting control
relays
all of these
An inverting op-amp with a feedback resistance of R, and another resistance of magnitude R, has a voltage gain of
- Rf/R1
R1/Rf
1+Rf/R1
1
A non-inverting op-amp with a feedback resistance of R, and another resistance R, has a
voltage gain of
- Rf/R1
R1/Rf
1+Rf/R1
1-Rf/R1
A negative feedback amplifier has 0.5% of output voltage feedback and antiphase with it. The gain of the amplifier then is 150. Calculate the amplifier gain without feedback.
A triode has an anode-slope resistance of 12 kQ and an amplification factor of 15. Determine the stage gain if it is used as an amplifier with an anode load consisting of a choke having a resistance of 20 k and an inductance of 7,500 μH when the input voltage has a frequency of 600 KHZ.
-12.17
-15.65
14.66
-29.21
The primary function of a fuse is to
open the circuit
prevent excessive currents
protect the line
protect the appliance
H.R.C. fuses provide best protection against
overload
reverse current
open-circuits
short-circuits
The basic function of a circuit breaker is to
produce arc
ionize the surrounding air
transmit voltage by arcing
extinguish the arc
In a circuit breaker, the time duration from the instant of the fault to the extinction of arc is known as
operating time
total clearing time
lag time
lead time
In a circuit breaker the time duration from the instant of fault to the instant of closing of contact is known as
recycle time
total time
gross time
reclosing time
The rating of the circuit breaker is usually determined on the basis of
symmetrical
line to line
single line to ground
double line to ground
Which of the following circuit breaker has high reliability and minimum maintenance?
oil circuit breaker
air blast circuit breaker
vacuum circuit breaker
SF6 circuit breaker
An isolator is installed
as a substitute for circuit breaker
always independent of the position of circuit breaker
generally on both sides of a circuit breaker
________ is used to prevent motorizing of the generator.
Directional current relay
Reverse power relay
Overcurrent relay
Overvoltage relay
For a detection of the occurrence of the severe synchronizing power surges
impedance relays are best suited
reactance relays are best suited
MHO relays are best suited
split-phase relays are best suited
21 is the device function number for this relay.
Undervoltage relay
Overvoltage relay
Distance relay
Directional power relay
Directional relays are based on flow of
power
current
voltage wave
all of these
The undervoltage relays are usually used for what protection of the electrical equipment?
feeder protection
motor protection
transformer protection
bus-bar protection
What is the equivalent IEEE device number for an under-voltage relay?
67
52
27
51
Thermal relays are often used in
generator protection
motor starters
transformer protection
none of these
hat is the type of relay that is intended to respond to the difference between incoming and outgoing
electrical quantities?
Directional
Differential
Subtractive
Distance
Which of the following protective device operates on the principle of Kirchhoff's Current Law?
Instantaneous Overcurrent Relay
Differential Protective Relay
Undercurrent Relay
AC Time Overcurrent Relay
What is the equivalent IEEE device number for a differential protective relay?
21
67
81
87
What is the IEEE device function number 50?
AC time overcurrent relay
Instantaneous overcurrent relay
AC circuit breaker
Differential protective relay
Over voltage protection is recommended for
hydro-electric generators
steam turbine generators
gas turbine generators
all of these
Which of the following relays is used in transformers?
Buchholz relay
Mho relay
Merz-Price relay
Translay relay
A Merz-Price protection is suitable for
transformers
alternators
gas turbine generators
all of these
A pilot exciter is provided on generators for which of the following reasons?
To excite the poles of main exciter
To provide requisite starting torque to main exciter
To provide requisite starting torque to generator
none of these
The method most commonly used for synchronizing the alterators in a power house is
dark lamp method
dark lamp method only
bright lamp method
bright lamp method and a synchroscope
Which of the following is not integral part of synchronous generator system?
Excitation system
Protection system
Prime mover
Distribution system
Which of the following is a prime mover?
Steam turbine
Solar energy
Electric heater
None of these
The transformer oil used in transformers provide
cooling and lubrication
insulation and lubrication
insulation and cooling
insulation, cooling and lubrication
Conservator of a transformer consists of
an air-tight metal drum fixed at the top of the tank
drum placed at the bottom of the tank
overload protection
none of these
An excellent indicator of the condition of the oil in the power transformer is obtained by dividing the IFT (interfacial tension) by the NN (neutralization number). This ratio is known as the
eutralization Number
Myers Index Number
Polarization Index Number
Transformer turn ratio
A device used to detect the impurities in insulating oil.
Oil tester
Hi-pot
Megger
Surge tester
Silica gel prevents moisture from entering the outdoor transformer tank. It is placed in
Conservator
Breather
Core
Windings
________- are auxiliary transformers used for metering or operation of auxiliary equipment
dry transformers
oil immersed transformers
current transformers
station service transformers
Varmeter when paired with other devices measures
diversity
power
load
demand
Which of the following can be measured by "Bolometers"?
factor?
Thermal radiations
Electrical signals
Optical inputs
Temperature inputs
Which of the following instruments is suited for high frequency measurements?
Dynamometer
Oscilloscope
Moving iron vane
Thermocouple
Pole mounting substations are also known as
outdoor type
indoor type
basement type
open type
Megger is an instrument to measure
very low resistance
insulation resistance
Q of a coil
inductance of a coil
A __________ is used to measure the stator winding temperature of the generator.
thermocouple
pyrometer
resistance thermometer
thermometer
In between the generating station and consumers a number of transformation and switching stations exist, these are called the
Switchgears
Substations
Intermediate substations
Transformation stations
Series capacitors are used to
improve the line voltage
compensate for line inductive reactance
compensate for line capacitive reactance
none of these
An ACSR conductor of size 48/7 means that
it has 48 strands of steel and 7 strands of aluminum
it has 7 strands of steel and 48 strands of aluminum
the conductor has 55 strands
the conductor has 41 strands
Bus coupler is very essential in
single bus
double bus, double breaker
arrangement.
main and transfer bus
all of these
Which of the following bus-bar schemes has the lowest cost?
Ring bus-bar scheme
Single bus-bar scheme
Breaker and a half scheme
Main and transfer scheme
Which of the following devices will receive voltage surge first travelling on the transmission line?
Lightning arresters
Relays
Step-down transformer
Switchgear
Where must the surge arrester be placed?
away from transformer
near circuit breaker
near air break switch
near transformer
The lightning arrester is installed
at the top of the building
at the bottom of the building
away from the building to be protected
at the centre of the building
Which of the following acts as a protection against high voltage surges due to lightning and
switching?
Horn gaps
Thermal overload relays
Breather
Conservator
