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