WorksheetsELECTRONIC CIRCUITS & DEVICES
Total questions: 59
Worksheet time: 30mins
a rotary converter is a single machine with ___.
one armature and one field
two armatures and one field
one armature and two fields
two armatures and two fields
a synchronous converter can be started ____.
by means of a small auxiliary motor
from AC side as induction motor
from DC side as DC motor
any of the above methods
what is the efficiency of full wave rectifier?
100%
90%
80%
70%
an unregulated power supply which consist of a transformer, a rectifier and a filter has some characteristics which are as follows EXCEPT one. which is it?
it has a good voltage regulation
it is relatively inexpensive
the output voltage varies with the load
output voltage depends on input voltage
the ripple factor of a power supply is a measure of ___.
its filter efficiency
diode rating
its voltage regulation
purity of power output
what is UPS stands for?
Uninterrupting Power Supply
Uninterruptible Power Supply
United Power System
Uninterruptible Portable Supply
if a transistor is operated in such a way that output current flows for 170 deg. of the input signal, then it is ___ operation.
class A
class B
class C
class AB
unit of a sound absorption coefficient of materials?
decibel
watts
erg
sabine
unit of measure of sound intensity level is ___
watts
decibel
erg
sabine
an SCR (silicon controlled rectifier) behaves as a ___ switch
bidirectional
mechanical
unidirectional
three-way
a TRIAC can pass a portion of ___ half-cycle through the load.
only positive
both positive and negative
only negative
none of these
a device that does not have a gate terminal is ____
triac
FET
SCR
diac
a device that exhibits negative resistance region is
SCR
triac
diac
UJT
a carrier current communication receiver is found where?
post office
substation
distributor
radio station
the philippine has adopted one of the following primary color television transmission standards. which one is this?
PAL
NTSC
EUREKA
SECAM
what is the frequency range for TV channels 2 to 13?
UHF
VHF
SHF
HF
a type of communication that uses light, rather than electricity to communicates is called
fiber-optic
microwave
laser carrier
power-line carrier
what is the optical source for the transmitting end of an optic fiber cable?
LED
photo cell
Halogen
Injection Laser
which one will accommodate more channels?
50 multiplexer
100 pair cable
100 chips
one fiber optics
a silicon controlled switch (SCS) has ___.
four layers and three terminals
two anodes and two gates
three layers and four terminals
one anode, one cathode & two gates
A LASCR is just like a conventional SCR, except that it ___.
cannot carry large current
has no gate terminal
can also be light-triggered
cannot be pulse triggered
voltage dependent resistor (VDR) are usually made from ____
nichrome
graphite
silicon carbide
carbon
in a crystal, an atom vibrates at a frequency determined by ___.
the heat content of the crystal
the stiffness of the bond it makes with neighbors
the valence of the crystal
the temperature of the crystal
what principle does the microphone operate?
audioelectric
piezoelectric
photoelectric
thermoelectric
an electronic oscillator is ___.
just like an alternator
an amplifier with feedback
nothing but an amplifier
a converter of AC to DC energy
it refers to a deevice that merely boosts a signal and passes it on:
repeater
amplifier
booster
op-amp
which of the following is reversible in action?
motor-generator set
motor converters
rotary converter
none of these
when a rotary converter is started by means of a small auxiliary motor. the power of motor must be.
less than the dc output of converter
less than the AC input of the converter
slightly more than the value of friction and windage losses at rated speed
half of dc output of converter
the following are advantages of motor-generator set over rotary converter. EXCEPT:
it can be used for power factor correction purposes
DC output voltage can be controlled easily by adjusting the field regulator
provided supply voltage
it has a comparatively high efficiency
in a 1-phase rotary converter the number of slip rings will be ___
2
1
4
3
a rotary converter operates at ___ power factor
low
high
zero
infinite
the turnaround from vacuum tube to solid state dynamic component in 1948 was triggered by the invention of the transistors by the three team men. which laboratory in U.S. did their work?
westinghouse
GE
bell telephone
philips
in reverse PN junction, with the voltage is increasing, the current is ___
increasing
decreasing
increasing exponentially
no change
it may be defined as the energy which corresponds to the center of gravity of conduction electrons and holes weighted according to their energies. it is in the middle of forbidden energy gap.
valence band
conduction band
kinetic energy
fermi level
which is NOT a semiconductor?
selenium
silica
gallium arsenide
carbon radium
tubes are preferred to transistors in the following applications EXCEPT one.
high power
high frequency
high voltage
long life
semiconductor materials have ___ bond.
metallic
ionic
covalent
mutual
a P-type semiconductor has storage of electron, what charge is it free?
intrinsic
electron
hole
proton
without a dc source, a clipper acts like a ____
rectifier
demodulator
clamper
chopper
the primary function of a clamper circuit is to ___
suppress variations in signal voltage
lower negative half-cycle of the signal
raise positive half-cycle of the signal
introduce a dc level into an AC signal
the basic reason why a full wave (FW) rectifier has twice the efficiency of a half wave (HW) rectifier is that ___
it makes use of transformer
its ripple factor is much less
it utilizes both half-cycle of the input
its output freq. is twice the line freq.
which stage of a DC power supply uses zener diode as the main component?
regulator
filter
rectifier
voltage divider
an ideal single phase full wave rectifier circuit has a non inductive resistance load. Negligible tube drop and no transformer losses, what is the rectification or conversion efficiency in percent?
100%
90%
80%
70%
what do you call the process electronically drying paint?
dielectric heating
convection
induction heating
emmisivity
a live room one whose interior finishing is such that reverberation time of sound is __ sec.
0
more than 5
less than 1
more than 1
which of the following Logic circuits is the fastest?
Resistor-transistor-logic (RTL)
Transistor-transistor-logic (TTL)
Variable-threshold-logic (VTL)
Diode-transistor-logic (DTL)
the gate voltage in a FET at which the drain current ID becomes zero is called ___.
active voltage
saturation voltage
cut-off voltage
pinch-off voltage
the main factor which differentiates a DE MOSFET from E-only MOSFET is the absence of:
insulated gate
channel
electrons
P-N junctions
what electrode in a junction transistor corresponds to the cathode in a vacuum tube?
drain
base
collector
emitter
piezoelectricity principle is applied in ONE of the following:
ultrasound equipment
thermometer
microphones
TV sets
in 1885, he used a long wire as antenna and develop a practical radio system
Benjamin Franklin
Marconi
Isaac Newton
Carl Siemen
it refers to a device that merely boosts a signal and passes it on:
repeater
amplifier
booster
op-amp
RJ45 is used for ___.
data
video
audio
CATV
what is the most common fiber optic cable?
single mode step index
multi mode step index
single mode grated index
multi mode graded index
what is the function of a transducer?
signal detection
amplification
voltage reduction
energy conversion
how many doped regions does a typical bipolar junction transistor (BJT) have?
one
two
three
four
an amplifier with a feedback loop or path for energy to propagate from the output back to the input is ___
regenerative feedback
degenerative feedback
feedback
AGC
the depletion region in a junction diode form what part of a capacitor ___
+ plate
- plate
dielectric
none of these
increasing the reverse bias on a varactor diode will cause its capacitance
decrease
increase
no change
either A or B
