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ELEX > REM B LVL 1 > Flashcards

REM B LVL 1 Flashcards

1
Q

Assertion (A): Silicon is less sensitive to
changes in temperature than
germanium.
Reason (R): It is more difficult to
produce minority carriers in silicon than
in germanium.

A. A is false but R is true
B. Both A and R are true but R is not a correct
explanation of A
C. Both A and R are true and R is correct
explanation of A

A

C. Both A and R are true and R is correct
explanation of A

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2
Q

Assertion (A): The conductivity of p type
semiconductor is higher than that of
intrinsic semiconductor.
Reason (R): The addition of donor
impurity creates additional energy levels
below conduction band.

A. A is false but R is true
B. A is true but R is false
C. Both A and R are true and R is correct
explanation of A
D. Both A and R are true but R is not a
correct explanation of A

A

D. Both A and R are true but R is not a
correct explanation of A

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3
Q

Which of the following is true for
Pentavalent impurities?

A. Have three valence electrons
B. Introduce holes when added to a
semiconductor material
C. Increase the conduction of a
semiconductror material

A

C. Increase the conduction of a
semiconductror material

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4
Q

When a diode in a center-tapped
rectifier opens, the output is

A. unaffected
B. 0V
C. half-wave rectified

A

C. half-wave rectified

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5
Q

What band is characterized by the
existence of the forbidden band narrow
enough to allow terminal transition in
the next allowed band?

A. Conductor
B. Plasma
C. Inductor

A

A. Conductor

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6
Q

A semiconductor diode is biased in
forward direction and carrying current I.
The current due to holes in p material is

A. less than I
B. 0
C. 0.5

A

A. less than I

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7
Q

Assertion (A): When a photoconductive
device is exposed to light, its bulk
resistance increases.
Reason (R): When exposed to light,
electron hole pairs are generated in the
photoconductive device.

A. A is true but R is false
B. Both A and R are true but R is not a correct
explanation of A
C. A is false but R is true

A

C. A is false but R is true

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8
Q

Fig. 8-12-5-A6 represents a…

(REM ELEX B LVL 1 FIGURE)

Fig. 8-12-5-A6

A. Varistor
B. Schottky diode
C. None of these choices
D. Diode rectifier

A

B. Schottky diode

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9
Q

If the capacitor from emitter to ground
in a Common Emitter amplifier is
removed, the voltage gain

A. increases
B. becomes erratic
C. decreases
D. is not affected

A

C. decreases

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10
Q

The SI units of transconductance is

A. Ohm
B. Volt/ ampere
C. Ampere/ volt

A

C. Ampere/ volt

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11
Q

In a common-emitter (CE) amplifier, the
capacitor from emitter to ground is
called the ___ capacitor.

A. tuning
B. coupling
C. bypass
D. decoupling

A

C. bypass

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12
Q

Which of the following models of diode equivalent circuit is represented by the given I-V characteristic curve?

(REM ELEX B LVL 1 FIGURE)

A. Hybrid model
B. Simplified Model
C. Ideal Diode Model
D. Piecewise Linear Model

A

B. Simplified Model

In simplified model, the value of rd is
neglected and hence, we get a high
value of current for voltage greater than
or equal to VT.

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13
Q

In a regulated supply, what term
describes how much change occurs in the output voltage for a given change in the input voltage?

A. ripple voltage
B. load regulation
C. line regulation
D. voltage regulator

A

C. line regulation

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14
Q

During the positive half-cycle of the
input voltage in a bridge rectifier,

A. two diodes are forward-biased
B. all diodes are forward-biased
C. all diodes are reverse-biased

A

A. two diodes are forward-biased

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15
Q

A Zener diode is in a ___
impedance region in the forward bias
while it has a ___ impedance region
in the reverse bias.

A. very large, low
B. low, low
C. very large, very large
D. low, very large

A

D. low, very large

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16
Q

Typical values of voltage amplification
for the common-base configurations
vary from ___ and the current gain
is always ___

A. 50 to 300, larger than 1
B. 50 to 300, less than 1
C. larger than 1, 50 to 300

A

B. 50 to 300, less than 1

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17
Q

The full-wave voltage doubler provides
___ filtering action than (as) the
half-wave voltage doubler.

A. None of these choices
B. better
C. poorer

A

B. better

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18
Q

In a voltage regulator network with fixed
RL and R, what element dictates the
minimum level of source voltage?

A. Vz
B. Iz
C. Tz

A

A. Vz

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19
Q

If the base current of a transistor
operates in the linear region increases,
the collector current ___ and the
emitter current ___

A. Decreases, decreases
B. Increases, increases
C. Increases, decreases
D. Increases, does not change

A

B. Increases, increases

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20
Q

In a PNP circuit, the collector:

A. Has an arrow pointing inward
B. Is biased at a small fraction of the base
bias
C. Is positive with respect to the emitter
D. Is negative with respect to the emitter

A

D. Is negative with respect to the emitter

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21
Q

In normal operation an n-p-n transistor
connected in common-base
configuration has

A. the collector at a lower potential than the
emitter
B. the emitter at a lower potential than the
base
C. the base at a lower potential than the
emitter

A

B. the emitter at a lower potential than the
base

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22
Q

In Fig. Fig. 12-5-9-A5.If R_E short-
circuited:
(REM ELEX B LVL 1 FIGURE)

Fig. 12-5-9-A5

A. the load line would be affected
B. the load line would be unaffected
C. neither the load line would be unaffected
and the load line would be affected
D. both the load line would be unaffected and
the load line would be affected

A

A. the load line would be affected

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23
Q

The most stable biasing technique used
is the

A. collector bias.
B. voltage-divider bias.
C. base bias.

A

B. voltage-divider bias.

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24
Q

The output, V-I characteristics of an
Enhancement type MOSFET has

A. only a saturation region
B. an ohmic region at low voltage value
followed by a saturation region at
higher voltages
C. only an ohmic region

A

B. an ohmic region at low voltage value
followed by a saturation region at
higher voltages

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25
Q

The input resistance of the base of a
voltage-divider biased transistor can be
neglected

A. only if the base current is much larger than
the current through R2 (the lower bias
resistor).
B. only if the base current is much smaller than the current through R2 (the lower bias resistor).
C. at all times.

A

B. only if the base current is much smaller than the current through R2 (the lower bias resistor).

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26
Q

How many individual pnp silicon
transistors can be housed in a 14-pin
plastic dual-in-line package?

A. 4
B. 14
C. 10

A

A. 4

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27
Q

Assertion (A): In a BJT, the base region
is very thick.
Reason (R): In p-n-p transistor most of
holes given off by emitter diffuse
through the base.

A. A is true but R is falseA is false but R is
true
B. A is false but R is true
C. Both A and R are true and R is correct
explanation of A

A

C. Both A and R are true and R is correct
explanation of A

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28
Q

For which of the following frequency region(s) can the coupling and bypass capacitors no longer be replaced by the short-circuit approximation?

A. Low-frequency
B. All of these choices
C. Mid-frequency

A

A. Low-frequency

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29
Q

The largest theoretical voltage gain
obtainable with a CC amplifier is

A. unity
B. 100
C. infinite
D. 10

A

A. unity

30
Q

In an RC coupled CE amplifier, when the
input frequency increases, which of
these are incorrect?

A. An RC coupled amplifier behaves like a low
pass filter
B. Voltage gain increases
C. Voltage gain decreases due to shunt
capacitance
D. Reactance CsH decreases

A

B. Voltage gain increases

When frequency increases, shunt
reactance decreases. The voltage drop
across shunt capacitance decreases
and net voltage gain decrease. RC
coupled amplifier acts as a low pass
filter at high frequencies.

31
Q

What is the purpose of using a
cascading transistor configuration?

A. Decrease current gain
B. Decrease voltage gain
C. Increase current gain
D. Increase voltage gain

A

D. Increase voltage gain

A circuit having a single transistor
configuration does not provide suitable
bandwidth or gain. The purpose of a
cascading transistor configuration is to provide an increase in the voltage gain.The total gain of a cascading transistor configuration is the product of the
voltage gains of the discrete stages.

32
Q

A number of op-amp stages can be
used to provide separate gains.

A. lacks data
B. True
C. False

A

B. True

33
Q

What is the advantage of using a
cascading transistor configuration?

A. High gain and high bandwidth
B. Low gain and high bandwidth
C. Low gain and low bandwidth

A

A. High gain and high bandwidth

A circuit having a single transistor
configuration does not provide suitable
bandwidth or gain. To overcome this
difficulty, we combine several
amplification stages. The cascading
transistor configuration theory is used
for high gain as well as high bandwidth.

34
Q

— build a multistage connection.

A. Neither inverting nor noninverting op-amp
circuits must be used to
B. Both inverting and noninverting op-amp
circuits can be used to
C. Only a noninverting op-amp circuit must be
used to

A

B. Both inverting and noninverting op-amp
circuits can be used to

35
Q

For any cascaded amplifier network,
which of these are incorrect?

A. The overall output resistance is less
than the lowest output resistance in all
amplifiers used
B. Overall input resistance is equal to the
input resistance of the first amplifier
C. Loading effect occurs

A

A. The overall output resistance is less
than the lowest output resistance in all
amplifiers used

In cascading, the output of one amplifier
is connected to the input of another
amplifier. It is used to increase gain
while obtaining desired values of input
and output resistances. Overall input
resistance is the same as input
resistance of the first amplifier and net output resistance is the same as output resistance of the last (n) amplifier in the network. When amplifiers are connected in cascade, then loading effect does occur.

36
Q

What is the need for bootstrap biasing?

A. To prevent a decrease in the input
resistance due to the biasing network
B. To prevent an increase in the input
resistance due to the biasing network
C. To prevent a decrease in the input
resistance due to the presence of multiple
BJT amplifiers

A

A. To prevent a decrease in the input
resistance due to the biasing network

A bootstrap biasing network is a special
biasing circuit used in the Darlington
amplifier to prevent the decrease in input resistance due to the biasing network being used. Capacitors and resistors are added to the circuit to prevent it from happening.

37
Q

How is the voltage gain measured in a
cascading transistor configuration?

A. Decibels
B. Ampere
C. Dimensionless

A

A. Decibels

The voltage gain is measured in terms
of decibels. The total voltage gain is
calculated as the product of individual
stages or as a sum of all the stages if
the gain calculated at each intermediate
stage was measured in decibels as well.

38
Q

A widlar current source is used

A. to get high value of Output
B. to get high value of CMRR
C. to get low value of current

A

C. to get low value of current

In the widlar current source Re is added
to emitter lead of transistor, which
consequently results in smaller output
current value.

39
Q

The purpose of a comparator is to

A. detect the occurrence of a changing input
voltage
B. amplify an input voltage
C. produce a change in output when an
input voltage equals a reference
voltage
D. maintain a constant output when the dc
input voltage changes

A

C. produce a change in output when an
input voltage equals a reference
voltage

40
Q

If you know an op-amp’s open-loop gain and nothing else, you can determine the closed-loop gain of

A. an inverting amplifier
B. a noninverting amplifier
C. a voltage-follower
D. none of the amplifier configurations
without additional information

A

C. a voltage-follower

41
Q

In selecting an op-amp, suppose you
have several choices. Of the CMRR
values listed, the most desirable is

A. 20 dB
B. 10 dB
C. 100 dB

A

C. 100 dB

42
Q

The feedback path in an ideal op-amp
integrator consists of a

A. capacitor
B. resistor and a capacitor in series
C. resonant circuit
D. resistor

A

A. capacitor

43
Q

The purpose of a comparator is to

A. produce a change in output when an
input voltage equals a reference
voltage
B. maintain a constant output when the dc
input voltage changes
C. detect the occurrence of a changing input
voltage

A

A. produce a change in output when an
input voltage equals a reference
voltage

44
Q

In an oscillator circuit, the feedback
should be:

A. As great as possible
B. Kept to a minimum
C. Just enough to sustain oscillation

A

C. Just enough to sustain oscillation

45
Q

A tapped coil is used in a (n):

A. Clapp oscillator
B. Hartley oscillator
C. Armstrong oscillator
D. Colpitts oscillator

A

B. Hartley oscillator

46
Q

Feedback oscillators operate on the
principle of

A. attenuation
B. signal feedthrough
C. positive feedback
D. negative feedback

A

C. positive feedback

47
Q

Negative feedback in an amplifier:

A. Is used in an Armstrong oscillator
B. Causes oscillation
C. Increases sensitivity
D. Reduces the gain

A

D. Reduces the gain

48
Q

In the Wien bridge oscillator, which of
the following is (are) frequency-
determining components?

A. C1 and C2
B. R1 and R2
C. None of these choices
D. R1, R2, C1, and C2

A

D. R1, R2, C1, and C2

49
Q

Which of the following improvements is(are) a result of the negative feedback in a circuit?

A. Better stabilized voltage gain
B. All of these choices
C. Higher input impedance

A

B. All of these choices

50
Q

Which of the following is not a
characteristic of the UJT?

A. negative resistance
B. peak-point voltage
C. bilateral conduction
D. intrinsic standoff ratio

A

C. bilateral conduction

51
Q

Thyristors can be used for control of

A. dc separately excited motor
B. dc shunt motor
C. all of these choices
D. dc series motor

A

C. all of these choices

52
Q

Your boss has asked you to recommend a thyristor that will enable you to turn it on with a pulse and also turn it off with a pulse. Which of the following should you recommend?

A. a triac
B. an SCR
C. a PUT
D. an SCS

A

D. an SCS

53
Q

Identify the triac.

(REM ELEX B LVL 1 FIGURE)

A. d
B. e
C. a
D. d

A

B. e

54
Q

You need a very efficient thyristor to
control the speed of an AC fan motor. A
good device to use would be

A. a triac
B. a 4-layer diode
C. a BJT
D. a PUT

A

A. a triac

55
Q

The converter circuit which employs turn on and turn off when the voltage and/or current through the device is zero at the instant of switching is ___

A. a conventional converter
B. none of these choices
C. a resonant converter
D. a zero switching circuit

A

C. a resonant converter

56
Q

You have a light-dimmer circuit using an SCR. In testing the circuit, you find that 1G = O mA and the light is still on. You conclude that the trouble might be one of the following:

A. the switch is faulty
B. the SCR is open
C. the gate circuit is shorted
D. this is normal; nothing is wrong

A

D. this is normal; nothing is wrong

57
Q

Which of the following is NOT an analog
device?

A. Thermocouple
B. Current flow in a circuit
C. Light switch
D. Audio microphone

A

C. Light switch

58
Q

An application of a(n) ___
is in a lighting system for power interruptions.

A. triac
B. diac
C. SCS
D. SCR

A

D. SCR

59
Q

What is the effect on properties of LDR
when light falls on it?

A. Its capacitance changes
B. Its resistance remains same
C. Its resistance changes

A

C. Its resistance changes

When light falls on LDR (Light
dependant resistor) its resistance
changes. It is inversely proportional to the intensity of light. When light falls on LDR, the resistance decreases and more current starts to flow through it. It is
used to measure the intensity of light.

60
Q

What are transducers?

A. They convert work to power
B. They convert energy from one form to
another
C. They convert power from one form to
another
D. They convert work from one form to
another

A

B. They convert energy from one form to
another

Transducer are devices that convert
energy from one form to another. This
energy can be either mechanical energy,
light energy, heat energy or any other
forms of energy.

61
Q

What type of energy conversion does a
piezoelectric transducer perform?

A. It converts mechanical energy to
electrical energy
B. It converts electrical energy to mechanical
energy
C. It converts mechanical energy to sound
energy
D. It converts sound energy to mechanical
energy

A

A. It converts mechanical energy to
electrical energy

A piezoelectric transducer converts
mechanical energy to electrical energy.
They are generally used to detect a
knock or any impulsive force. They are
also used in electronic drum pads to
detect the impulse provided by the
drumsticks.

62
Q

PLC operates on the following signals

A. Digital
B. Analog
C. Frequency

A

A. Digital

63
Q

Which of the following are criteria for selecting a PLC or Programmable Logic Controller?
1. Input and output capacity 2. Size of memory needed 3. Speed and power of CPU 4. Physical and environmental conditions

A. 1,2, and 3 only
B. 1.2,3, and 4
C. 1 and 3 only

A

B. 1.2,3, and 4

64
Q

Solid State Relays (SSRs) have a

A. scr
B. optocoupler
C. none of these choices

A

B. optocoupler

65
Q

In a ladder logic, the given symbol is
used to indicate ___

A. Heating element
B. Relay coil
C. Fuse

A

A. Heating element

66
Q

The design concept of using building blocks of circuits in a PLD program is called a(n):

A. digital design
B. architectural design
C. verilog
D. hierarchical design

A

D. hierarchical design

67
Q

HVDC transmission has ___ as
compared to HVAC transmission.

A. smaller conductor size
B. smaller transformer size
C. smaller power transfer capabilities

A

A. smaller conductor size

68
Q

In an analog switch, the aperture time is
the time it takes for the switch to fully ___ after the control switches from ___

A. Close, sample to hold
B. Open, sample to hold
C. Close, hold to sample

A

B. Open, sample to hold

69
Q

Which of the following best describes
statement 1 and 2?
Statement A: Thyristors can be used in controlled heating, excitation systems of alternators, speed control of motors and HVDC.
Statement B: A static variable system using thyristors is very commonly used in high voltage AC systems.

A. Both statements are correct and B is
correct explanation of A
B. Both statements are correct but B is
not a correct explanation of A
C. One of the statement is wrong

A

B. Both statements are correct but B is
not a correct explanation of A

70
Q

In HVDC transmission lines

A. both the stations operate as a converter
B. one acts as a converter and other as an
inverter
C. both the stations operate as an inverter

A

B. one acts as a converter and other as an
inverter

71
Q

A static excitation system uses

A. transformer and ac exciter
B. transformer and dc exciter
C. transformer and thyristors
D. dc exciter and ac exciter

A

C. transformer and thyristors

ELEX (13 decks)

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