MULTIPLE CHOICE QUESTIONS WITH ANSWERS ON POWER ELECTRONICS AND
DRIVES[Q-1] Silicon based rectifiers are preferred than germanium
based rectifiers because(a) Si is available easily compared to
Ge(b) Only Si has a stable off state(c) Ge is very temperature
sensitive(d) Si only has the characteristics 1 + 2 < 1 at low
collector currents and reaches 1 at high currentsWhich of the above
statements are true?Options:1. A, B, D2. B, D3. B Only4. D Only5.
None of the above optionsAns: 2
[Q-2] In a triac,(a) The triggering pulse to main terminal 1
should be of the same polarity as the anode potential between MT1
and MT2(b) The triggering pulse should be of opposite polarity to
that of anode potential(c) When the triggering pulse is positive
and anode is positive, it is operating in the first quadrant(d)
When the triggering pulse is negative and anode is negative its
sensitivity is highest.Which of the above statements are
true?Options:1. A, D2. A, C3. C, D4. A, C, D5. None of the above
options
Ans: 4
[Q-3] In a single phase full wave SCR circuit with R, L load(a)
Power is delivered to the source for firing angle of less than
90(b) The scr changes from inverter to converter at = 90(c) The
negative dc voltage is maximum at = 180(d) To turn off the scr, the
maximum delay angle must be less than 180Which of the above
statements are true?Options:1. C, D2. C Only3. D Only4. A , B5.
None of the above options
Ans: 1[Q-4] While comparing triac and scr,(a) Both are
unidirectional devices(b) Triac requires more current for turn on
than scr at a particular voltages(c) A triac has less time for turn
off than SCR(d) Both are available with comparable voltage and
current ratingsWhich of the above statements are true?Options:1. A,
C2. B, C3. A, B4. D Only5. None of the above options
Ans:2[Q-5] Which of the following statements are true(a) If the
SCR, even with proper gate excitation and anode-cathode voltage
does not conduct for a particular load resistance, then it wouldbe
necessary to decrease the load resistance to turn ON the SCR(b) The
SCR would be turned OFF by voltage reversal of the applied
anode-cathode ac supply of frequencies up to 30kHz(c) If the gate
current of the SCR is increased, then the forward breakdown voltage
will decrease
Options1. A, B, C2. B, C3. A , C4. A, B5. None of the above
options
Ans: 3
[Q-6] Which of the following statements are trueWhen gate
triggering is employed, a SCR can withstand higher values of di/dt,
if the1. Gate current is increased2. Rate of rise of gate current
is increased3. Gate current is increased4. Rate of rise of gate
current is decreasedOPTIONS:(a) 3, 4(b) 1, 4(c) 2, 3(d) 1, 2(e)
None of the above options
Ans: A[Q-7] In a SCR based converter, the free wheeling diode is
used to(a) Add to the conduction current of thyristors(b) Oppose
the SCR conduction(c) Conduct current during the OFF period of the
SCR(d) Protect the SCR by providing a shunt pathAns:CPower
Electronics Objective Questions with Answers: [1] " Six MOSFETs
connected in a bridge configuration (having no other power device)
MUST be operated as a Voltage Source Inverter (VSI) ". This
statement is [GATE-2007]A. True, because beingmajoritycarrier
devices, MOSFETs are voltage drivenB. True, because MOSFETs have
inherently anti parallel diodesC. False, because it can be operated
both as current source Inverter (CSI) or a VSID. False, because
MOSFETs can be operated as excellent constant current sources in
the saturation regionAns: D[2] A single phase full - wave half
controlled bridge converter feeds an inductive load. The two SCRs
in the converter are connected to a common DC bus. The converter
has to have a free wheeling diode [GATE-2007] A. because the
converter inherently does not provide for free wheelingB. Because
the converter does not provide for free wheeling for high values of
triggering anglesC. Or else the free wheeling action of the
converter will cause shorting of the AC supplyD. Or else if a gate
pulse to one of the SCRs is missed, it will subsequently cause a
high load current in the other SCRAns: B[3] The power electronic
converter shown in the figure has a single pole double throw
switch. the pole P of the switch is connected alternately to throws
A and B. The converter shown is a [GATE-2010]
A. Step down chopper( buck converter)B. Half- wave rectifierC.
Step Up chopper ( boost converter)D. Full wave converterAns: A[5]
The fully controlled thyristor converter in the figure is fed from
a single-phasesource. When the firing angle is 0, the dc output
voltage of the converter is 300V. What will be the output voltage
for a firing angle of 60, assuming continuousconduction?
[GATE-2010]
(A) 150V(B) 210V(C) 300V(D) 100VAns: AAnswer[6] The manufacturer
of a selected diodegives the rate of fall of the diode current
di/dt = 20 A/ms, and a reverse recovery time of trr =5 ms.What is
value of peak reverse current?
Ans: 44.72AThe peak reverse current is given as:
The storage charge QRR is calculated as Qrr = (1/2)*(di/dt)*
SQU.(trr)= 1/2 X 20A/uS X 5u X 5u = 50uC.substitute the Qrr value
in Irr equation.
[8] Circuit turn-off time of an SCR is defined as the time
[GATE2011]A. Taken by the SCR to turn offB. Required for SCR
current to become zeroC. For which the SCR is reverse biased by the
commutation circuitD. For which the SCR is reverse biased to reduce
its current below the holding currentAns: C[9] A single phase fully
controlled thyristor bridge ac-dc converter is operating at a
firing angle of 25 degree, and an overlap angle 10 degree with
constant dc output current of 20A. The fundamental power factor (
displacement factor) at input ac mains is [GATE2007]A. 0.78B.
0.827C. 0.866D. 0.9Ans:A[10] A three phase fully controlled
thyristor bridge converter is used as line commutated inverter to
feed 50KW power at 420 V DC to a three phase 415V(line), 50Hz as
mains. Consider Dc link current to be constant. The rms current of
the thyristor is [GATE2007]A. 119.05AB. 79.37AC. 68.73AD. 39.68A
Ans:D
[1] In a uniform electric field, field lines and equipotentials
[Gate 1997 ]a) Are parallel to one anotherb) Intersect at 45 degc)
Intersect at 30 degd) Are orthogonalAns:D[2] For a pulse
transformer, the material used for its core and the possible turn
ratio from primay to secondary are respectively(a) ferrite; 20:1(b)
laminated iron; 1:1(c) ferrite; 1:1(d) powdered iron; 1:1Ans: C[3]
The capacitance of a reverse biased junction of a thyristor is 20
picofarad. The charging current of this thyristor is 4mA. The
limiting valueof dv/dt is .....V/uSAns:200[4] When the induction
motor runs at synchronous speed the voltage induced in the rotor of
it is(a) Very near input voltage to stator(b) Slip time the input
voltage(c) Zero(d) None of the aboveAns:C[5] Chopper control for
the DC motor provides variation in(a) Input voltage(b) Frequency(c)
None of the aboveAns: A
[6] While comparing SCR with BJT, which of the following is
true(a) SCR requires turn off circuit while BJT does not(b) The
voltage drop of SCR is less than BJT(c) SCR requires a continuous
gate current(d) BJT draws continuously base currentWhich of the
above statements are true?(1) a only(2) d only(3) a, d(4) b, d
Common Data Questions: 7 & 8In the 3-phase inverter circuit
shown, the load is balanced and the gating scheme is 180-conduction
mode.All the switching devices are ideal
[7] The rms value of load phase voltage is[GATE2012]a. 106.1Vb.
141.4Vc. 212.2Vd. 282.8V
Ans: B[8] If the dc bus voltage Vd=300V, the power consumed by
3-phase load is[GATE2012]a. 1.5kWb. 2.0kWc. 2.5kWd. 3.0kW
Ans: D
[9] The typical ratio of latching current to holding current in
a 20A thyristor is[GATE 2012]a. 5.0b. 2.0c. 1.0d. 0.5
Ans: B
[10] A half-controlled single-phase bridge rectifier is
supplying an R-L load. It is operated at a firingangleand the load
current iscontinuous. Thefraction of cycle that the freewheeling
diodeconducts is[GATE 2012]a. 1/2b. (1-/)c./2d./
Ans: D
[11]For power factor correction of power systems which one is
used:(a) capacitor(b)inductor(c) resistorsAns: A
[12] Which type of motor used in home ceiling fan:(a) capacitor
motor(b) shaded pole motor(c) universal motor(SPLIT PHASE CAPACITOR
MOTOR)Ans: A
[13] Op-amp (operational amplifier) input resistance:(a) Zero(b)
Infinity(c) Relative resistance(d) Same output resistanceAns:B
[14] For an inverter op-amp, what will be the equivalent output
resistance?(a) Zero(b) Infinity(c) Relative forward resistance(d)
Same as the input resistance
Ans: ASOLVED OBJECTIVE QUESTIONS FROM DC MACHINES:[1] Voltage
equation of a dc motor isA. V = Eb + IaRaB. Eb= V + IaRaC. V =
Eb/IaRaD. V = Eb + Ia2RaE. None of the aboveAns: A[2] Both
Hopkinson's test and Field testA. Require two electrically coupled
series motorsB. Need two similar mechanically coupled motorsC. Use
negligible powerD. Are regenerative testsE. None of the
aboveAns:B[3] which of the following motor has the constant
speed?A. Series motorB. Shunt motorC. Cumulatively compound motorD.
All of the aboveE. None of the aboveAns:B
4] The usual test to find the efficiency of the traction motor
isA. Field's testB. Retardation testC. Hopkinson's testD.
Swinburn's testE. None of the aboveAns: A[5] A DC series motor is
best for drivingA. LathesB. Cranes and hoistsC. Shears and
punchesD. Machine toolsE. None of the aboveAns: B
[6] Retardation test on a dc shunt motor is used for findingA.
Stray lossB. Copper lossC. Friction lossD. Iron lossE. None of the
aboveAns: A[7] In a DC series motor increasing the load current
willA. Decrease the speedB. Increase the speedC. Better
commutationD. Increase the back emfE. None of the aboveAns: A[8]
One of the main advantage of the swinburn's test isA. It is
applicable both shunt and compound motorsB. It needs one running
testC. It is very economical and convenientD. It ignores any charge
in iron lossE. None of the aboveAns:C[9] the main disadvantage of
hopkinson's test for finding efficiency of shunt dc motors is that
itA. Requires full load powerB. Ignores any change in iron lossC.
Needs one motor and one generatorD. Requires two identical shunt
machinesE. None of the aboveAns D
[10] The most economical method of finding no losses of a large
dc shunt motor isA. Hopkinson's testB. Swinburn's testC.
Retardation testD. Field's testE. None of the above
Ans: B
SYNCHRONOUS MOTOR OBJECTIVE QUESTIONS WITH ANSWERS:[1] In a
synchronous motor, damper winding is provided toA. Stabilize rotor
motionB. Suppress rotor oscillationsC. Develop necessary starting
torqueD. Both B and CAns: D[2] Synchronous capacitor isA. An
ordinary static capacitor bankB. An over excited synchronous motor
driving mechanical loadC. An over excited synchronous motor running
without mechanical loadD. None of the aboveAns:C
[3] A synchronous machine is called as doubly excited machine
becauseA. It can be over excitedB. It has two sets of rotor polesC.
Both its rotor and stator are excitedD. It needs twice the normal
exciting currentAns: C
[4]If the field of a synchronous motor is under excited, the
power factor will beA. LaggingB. LeadingC. UnityD. More than
unityAns: A
[5] The direction of rotation of a synchronous motor can be
reversed by reversingA. Current to the field windingB. Supply phase
sequenceC. Polarity of rotor polesD. None of the aboveAns: B[6]A
synchronous motor connected to infinite busbars has at constant
full-load, 100% excitation and unity pf. On changing the excitation
only, the armature current will haveA. Leading pf with
under-excitationB. Leading pf with over excitationC. Lagging pf
with over excitationD. No change of pfAns: B
7] The maximum value of torque angle a in a synchronous motor
is.......degrees electricalA. 45B. 90C. Between 45 and 90D. Below
60Ans: B
[8] The angle between the synchronous rotating stator flux and
rotor poles of a synchronous motor isA. Synchronizing angleB.
Torque angleC. Power factor angleD. Slip angleAns:B[9] In a
synchronous machine when the rotor speed becomes more than the
synchronous speed during hunting, the damping bars developA.
Synchronous motor torqueB. DC motor torqueC. Induction motor
torqueD. Induction generator torqueAns: D[10] When load on a
synchronous motor is increased its armature current is increased
provided it isA. Normally excitedB. Over excitedC. Under exciterD.
All of the aboveAns:D
MEASUREMENTS AND INSTRUMENTATION OBJECTIVE QUESTIONS WITH
ANSWERS[1] A rectifier type instrument is connected to 100VDC and
is operated in the DC measuring module reads(a) 111V(b) 90V(c)
50V(d) 100VAns: A
[2] A permanent magnet moving coil ammeter has a coil resistance
of 99ohm and Full Scale Deflection(FSD) current of 0.1mA. Shunt
resistance is 1 ohm. Current through the meter at 0.5 F.S.Dis(a)
0.007mA(b) 0.05mA(c) 0.023mA(d) 0.1mAAns: B[3] One single phase
wattmeter operating on 230V and 5A for 5 hours makes 1940
revolutions. Meter constant in revolutions is 400. What is the
power factor of the land?(a) 1(b) 0.84(c) 0.73(d) 0.65Ans:B[4] For
power measurement of three phase circuit by two wattmeter method,
when the value of power factor is less than 0.5 lagging(a) one of
the wattmeters will read zero(b) both give the same readings(c) one
of the wattmeter connections will have to be reversed(d) pressure
coil of the wattmeter will become ineffective.Ans:C[5] When using
ohmmeter, applied voltage is to be disconnected from the circuit
because(a) Voltage source will increase resistance(b) Current will
decrease resistance(c) the ohmmeter has its own internal battery(d)
non of the aboveAns: C[6] Which wave has the least form factor?(a)
Square wave(b) Rectangular wave(c) Sine wave(d) Triangular waveAns:
A[7] With a sweep time 10ms across the screen the approx.
horizontal sawtooth frequency will be(a) 50Hz(b) 100Hz(c) 1kHz(d)
500HzAns: B[8] A spring controlled indicating instrument has a
deflection of 90deg for maximum current I. The corresponding
deflection for a gravity controlled instrument is(a) 90(b) 120(c)
30(d) 0Ans: C[9] It is found that 10A current passes through a
resistor of 10ohms. The resistor has 5% tolerance . The error in
measurement of current can be as high as 5%. What is max error in
measurement of power, calculated from measured value of I and the
nominal value of resistor?(a) 100 W(b) 150W(c)50W(d) 200WAns: B[10]
A resistor of 10Kohms with 5% tolerance is connected in parallel
with a 5Kohms resistor of 10% tolerance. What is the tolerance
limit for the parallel network?(a) 5%(b) 6.67%(c) 10%(d) 8.33%Ans:
D
[11] The resistance offered to the passage of an in-varying
current by a column of mercury at the temperature of melting ice of
mass 14.4521 gms of uniform cross-sectional area and length 106.3cm
is(a) Standard ohm(b) One international ohm(c) One ohm according to
SI units(d) One ohm according to working standardsAns: B
Electrical Machines - Alternators : Part 8[1] Squirrel cage bars
placed in the rotor pole faces of an alternator help reduce
hunting(a) Above synchronous speed only(b) Below synchronous speed
only(c) Above and blow synchronous speeds both(d) None of the
aboveAns: C
[2] The stationary alternator should not be connected to live
bus-bars because it(a) Is likely to run as synchronous motor(b)
Will get short - circuited(c) Will decrease bus - bar voltage
though momentarily(d) Will disturb generated emf's of other
alternators connected in parallel.Ans:B [3] With a unity load p.f,
the effect of armature reaction on the main field flux of an
alternator is(a) Distortional(b) Magnetising(c) Demagnetising(d)
NominalAns: A
[4] At lagging loads, armature reaction in an alternator is(a)
Cross-magnetising(b) Demagnetising(c) Non-effective(d)
MagnetisingAns:D[5] The frequency of voltage generated by an
alternator having 4 poles and rotating at 1800 rpm is(a) 60 Hz(b)
7200Hz(c) 120Hz(d) 450HzAns: A[6] The main disadvantages of using
short pitch winding in alternators is that it(a) Reduces harmonics
in the generated voltage(b) Reduces the total voltage around the
armature coils(c) Produces asymmetry in the three phase windings(d)
Increases Cu of end connections.Ans: B[7] Zero power factor method
of an alternator is used to find its(a) Efficiency(b) Voltage
regulation(c) Armature resistance(d) Synchronous impedanceAns:
B
[8] Armature reaction in an alternator mainly affects(a) Rotor
speed(b) Terminal voltage per phase(c) Frequency of armature
current(d) Generated voltage per phaseAns: D[9] The effect of
increasing air gap length in the induction motor will increase
the(a) Power factor(b) Speed(c) Magnetising current(d) Air gap
fluxAns: C
[10] The principle of operation of a 3 phase induction motor is
most similar to that of a(a) Synchronous motor(b) Repulsion start
induction motor(c) Transformer with a shorted secondary(d)
Capacitor start, induction run motorAns: C
BASIC ELECTRONICS MULTIPLE CHOICE QUESTIONS: PART-6[1] A network
designed to pass signals with all frequencies except those between
two specified cut-off frequencies is called a(a) low-pass filter(b)
high-pass filter(c) band-pass filter(d) band-stop filterAns: D
[2] A low-pass T-connected symmetrical filter section has an
inductance of 200mH in each of its series arms and a capacitance of
0.5 F in its shunt arm. The cut-off frequency of the filter is(a)
1007 Hz(b) 251.6 Hz(c) 711.8 Hz(d) 177.9 HzAns: C
[3] A low-pass -connected symmetrical filter section has an
inductance of 200mH in its series arm and capacitances of 400 pF in
each of its shunt arms. The cut-off frequency of the filter is(a)
25.16 kHz(b) 6.29 kHz(c) 17.79 kHz(d) 35.59 kHzAns:A[4] A high-pass
T-connected symmetrical filter section has capacitances of 400 nF
in each of its series arms and an inductance of 200mH in its shunt
arm. The cut-off frequency of the filter is(a) 1592 Hz(b) 1125
Hz(c) 281 Hz(d) 398 HzAns:D
[5] A high-pass -connected symmetrical filter section has a
capacitance of 5000 pF in its series arm and inductances of 500 H
in each of its shunt arms. The cut-off frequency of the filter
is(a) 201.3 kHz(b) 71.18 kHz(c) 50.33 kHz(d) 284.7 kHzAns:B
[6] A network designed to pass signals at frequencies above a
specified cut-off frequency is called a(a) low-pass filter(b)
high-pass filter(c) band-pass filter(d) band-stop filterAns: B[7] A
network designed to pass signals at frequencies below a specified
cut-off frequency is called a(a) low-pass filter(b) high-pass
filter(c) band-pass filter(d) band-stop filterAns: A[8] A network
designed to pass signals with frequencies between two specified
cut-off frequencies is called a(a) low-pass filter(b) high-pass
filter(c) band-pass filter(d) band-stop filterAns: C
The following refers to questions 9 and 10.A filter section is
to have a nominal impedance of 620 and a cut-off frequency of 2
MHz.
[9] A low-pass T-connected symmetrical filter section is
comprised of(a) 98.68 H in each series arm, 128.4 pF in shunt
arm(b) 49.34 H in each series arm, 256.7 pF in shunt arm(c) 98.68 H
in each series arm, 256.7 pF in shunt arm(d) 49.34 H in each series
arm, 128.4 pF in shunt arm
Ans: B
[10] A low-pass -connected symmetrical filter section is
comprised of(a) 98.68 H in each series arm, 128.4 pF in shunt
arm(b) 49.34 H in each series arm, 256.7 pF in shunt arm(c) 98.68 H
in each series arm, 256.7 pF in shunt arm(d) 49.34 H in each series
arm, 128.4 pF in shunt armAns: AELECTRONICS DEVICES OBJECTIVE TYPE
QUESTIONS[1] A Zener diode is used fora)Voltage
Regulationb)Rectificationc)Noise Suppressiond)Blocking A.C
Ans: Voltage Regulation[2] An SCR is a device havinga)Three
layers with four junctionsb)Three layers with two junctionsc)Four
layers with three junctionsd)Two layers with three junctions
Ans: Four layers with three junctions[3] An amplifier has a gain
of 10,000 expressed in decibels the gain isa)10b)40c)80d)100
Ans: 80[4] An emitter follows hasa)High input impedance and high
output impedance.b)High input impedance and low output
impedance.c)Low input impedance and high output impedance.d)Low
input impedance and low output impedance.
Ans:High input impedance and low output impedance.
[5] Semi-conductor diode time constant is equal toa)The value of
majority carrier life timeb)The life time of minority carrierc)The
diffusion capacitance time constantd)Zero
Ans: The value of majority carrier life time[6]To prepare a P
type semiconducting material the impurities to be added to silicon
area)Boron, Galliumb)Arsenic, Antimonyc)Gallium,
Phosphorousd)Gallium, Arsenic
Ans:Boron, Gallium[7]FET is a good signal chopper becausea)It
exhibits no offset voltage at zero drain currentb)It occupies less
space in integrated formc)It is less noisyd)It has got high input
impedance
Ans: It exhibits no offset voltage at zero drain current
[8]In Bipolar Junction transistors, the type of configuration
which will give both voltage gain and current gain
isa)CCb)CBc)CEd)None
Ans: CE
[9]To increase the input resistance and decrease the output
resistance in negative feedback, the type used isa)Voltage
Shuntb)Current Seriesc)Voltage Seriesd)Current Shunt
Ans: Voltage Series
[10] A series capacitance used in a filter circuit
representsa)Low-Passb)Band-Passc)High-Passd)NoneAns: High-Pass
[11] An ideal power supply is characterized bya) Very large
output resistanceb) Very small output resistancec) Zero internal
resistanced) Infinite internal resistance
Ans: C[12] An ideal diode should havea) Zero resistance in the
forward bias as well as reverse biasb) Zero resistance in the
forward bias and an infinitely large resistance in reverse biasc)
Infinitely large resistance in reverse biasd) Infinitely large
resistance in forward as well as reverse bias
Ans: B[13] One coulomb-per-second is equal to one:a) Wattb)
Joulec) Voltd) Ampere
Ans:D[14] Which of the following is one of the functions
performed by a diode?a) Filterb) Amplifierc) Rectifierd)
Inverter
Ans: C[15] What is the power factor?a) Ratio of true power to
apparent powerb) Peak power times 0.707c) Sin of the phase
difference between E and Id) Cos of the phase angle between true
power and apparent powerAns:A
CONTROL SYSTEM SOLVED COMPETITIVE QUESTIONS:[1] An open loop
system represented by the transfer function G(s) = (s-1) /
(s+2)(s+3) is(a) Stable and of the minimum phase type(b) Stable and
of the non-minimum phase type(c) Unstable and of the minimum phase
type(d) Unstable and of the non-minimum phase type
Ans:B
[2] The open loop transfer function G(s) of a unity feedback
control system is given as,G(s) = [ k(s+2/3) / s2(s+2) ]From the
root locus, it can be inferred that when k tends to positive
infinity,(a) Three roots with nearly equal real parts exist on the
left half of the s-plane(b) One real root is found on the right
half of the s-plane(c) The root loci cross the jaxis for a finite
value of k; k0(d) Three real roots are found on the right half of
the s-plane
Ans:A[3] Given that
then the value of A3is[GATE2012](a) 15A+12I(b) 19A+30I(c)
17A+15I(d) 17A+21I
Ans:B
[5] The input x(t) of a system are related as y(t) =
t-x()cos(3)d.The system is[GATE2012](a) Time-invariant and
stable(b) Stable and not time-invariant(c)
Time-invariantandnotstable(d) Not time-invariant and not stable
Ans: B
[6]The feedback system shown below oscillates at 2 rad/s
when[GATE2012]
(a) k=2 and a=0.75(b) k=3 and a=0.75(c) k=4 and a=0.5(d) k=2 and
a=0.5
Ans: A[7] The Fourier transform of a signal h(t) is H(j) =
(2cos)(sin2)/. The value of h(0) is[GATE2012](a) 1/4(b) 1/2(c) 1(d)
2
Ans: C
[8] The state variable description of an LTI system is given
by
where y is the output and u is the input.The system is
controllable for,[GATE2012](a) a10,a2=0,a30(b) a1=0,a2=0,a30(c)
a1=0,a2=0,a3=0(d) a10,a20,a3=0
Ans:D
[9] The state transition diagram for the logic circuit shown
is[GATE2012]
Ans: D[10] Given that
then the value of A3is[GATE2012](a) 15A+12I(b) 19A+30I(c)
17A+15I(d) 17A+21I
Ans: B
[11] The differentiator has a transfer function whose [Gate
1997](a) Phase increases linearly with frequency(b) Amplitude
remains constant(c) Amplitude increases linearly with frequency(d)
Amplitude decreases linearly with frequency
Ans: A[12] Introduction of integral action in the forward path
of a unity feedback system results in a [Gate 1997](a) Marginally
stable system(b) System with no steady state error(c) System with
increase stability margin(d) System with better speed of
response
Ans: ADigital Electronics objective Questions: Part 1[1] It is
required to construct a counter to count upto 100(decimal). The
minimum number of flipflops required to construct the counter isa)
8b) 7c) 6d) 5Ans:A [2] The gate that assumes the 1 state, if and
only if the input does not take a 1 state is called........a) AND
gateb) NOT gatec) NOR gated) Both b and c
Ans: D
[3] For NOR circuit SR flip flop the not allowed condition
is....a) S=0, R=0b) S=0, R=1c) S=1, R=1d) S=1, R=0
Ans: C . When S=R=1 the output is subject to unpredictable
behaviour when S and R return to 0 simultaneously.[4] A bistable
multivibrator is aa) Free running oscillatorb) Triggered
oscillatorc) Saw tooth wave generatord) Crystal oscillator
Ans: B
[5] For a large values of |VDS|, a FET behave asa) Voltage
controlled resistorb) Current controlled current sourcec) Voltage
controlled current sourced) Current controlled resistorAns: C
[6] When a step input is given to an op-amp integrator, the
output will bea) a rampb) a sinusoidal wavec) a rectangular waved)
a triangular wave with dc biasAns: A
[7] In a full-wave rectifier without filter, the ripple factor
isa) 0.482b) 1.21c) 1.79d) 2.05Ans: A
[8] Hysteresis is desirable in Schmitt-trigger, becausea) Energy
is to be stored/discharged in parasitic capacitanceb) Effects of
temperature would be compensatedc) Devices in the circuit should be
allowed time for saturation and desaturationd) It would prevent
noise from causing false triggeringAns:C
[9] For a 10-bit DAC, the Resolution is defined by which of the
followinga) 1024b) 1/1024c) 10d) NoneAns:B[10] SRAM full form isa)
Serial Read Access Memoryb) Static Random Access Memoryc) Static
Read-only Access memoryAns: B
[11] What are the minimum number of 2 to 1 multiplexers required
to generate a 2 input AND gate and a 2 input Ex-OR gate?a) 1 and
2b) 1 and 3 c) 1 and 1 d) 2 and 2Ans:A
[12]The output of a logic gate is 1 when all its inputs are at
logic 0. Then gate is eithera) A NAND or an EX-OR gateb) A NOR or
an EX-NOR gatec) An OR or a EX-NOR gated) An AND or an Ex-OR
gateAns: B
[13] A PLA can be useda) As a microprocessorb) As a dynamic
memoryc) To realise a sequential logicd) To realise a combinational
logicAns: D[14] A dynamic RAM consists ofa) 6 Transistorsb) 2
Transistors and 2 Capacitorsc) 1 Transistor and 1 Capacitord) 2
Capacitor onlyAns:C
[15] When a CPU is interrupted, ita) Stops execution of
instructionsb) Acknowledges interrupt and branches of subroutinec)
Acknowledges interrupt and continuesd) Acknowledges interrupt and
waits for the next instruction from the interrupting device.Ans:
B