ies electronics paper
DESCRIPTION
IES ECE 2012 EXAM PAPERTRANSCRIPT
Indian Engineering Services 2012 Electronics Engg paper
• A piece of writing paper that is 10 cm wide,15cm long and 0.05mm thick has a dielectric strength of 8 kV/mm. If it is placed between two copper plates and subjected to an increasing voltage, it will break down at
• 8 kV• 4 kV• 0.4 kV• 0.8 kV
Answer -- 0.4 kV
• In a transconductance,the device output• voltage depends upon the input voltage• voltage depends upon the input current• current depends upon the input voltage• current depends upon the input current
Answer -- current depends upon the input voltage
• A flux of 1.2 mWb exerts in a magnet having a cross-section of 30 cm2.The flux density in tesla is
• 4• 0.4• 2.5• 40
Answer -- 0.4
• If the drift velocity of holes under a field gradient of 200V / m is 100 m/s, their mobility in SI units is
• .5• .05• 50• 500
Answer -- .5
• Superconductors are becoming popular for their use in• generating very strong magnetic fields• manufacture of bubble memories• generating electrostatic field• generating regions free from magnetic field
Answer -- generating very strong magnetic fields
• Non-polar electrolytic capacitor(a)are used for a applications in AC circuits without any DC polarizing voltage(b)contain two capacitors connected in series with opposing polarities
• Both(a) and (b) are correct• Both (a) and (b) are wrong
Answer -- Both (a) and (b) are wrong
• The probability cumulative distribution function must be monotone and• increasing• decreasing• non-increasing• non-decreasing
Answer -- non-decreasing
• The discrete time system described by y(n) = x(n) to the power 2 is• causal and linear• causal and non-linear• non-causal and linear• non-causal and non-linear
Answer -- causal and non-linear
• The function which has its Fourier transform,Laplace transform and Z-transform unity is• Gaussian• impulse• sine• pulse
Answer -- impulse
• The property of Fourier transforms which states that the compression in time domain is equivalent to expansion in the frequency domain is
• duality• Scaling• time Scaling• frequency shifting
Answer -- time Scaling
• The Fourier transform of a rectangular pulse is• another rectangular pulse• triangular pulse• sine function• impulse function
Answer -- sine function
• A two-port network has parameters ABCD. If all the impedance in the network are doubled, then
• A and D remain unchanged,R is doubled and C is halved• A,B,C and D are all doubled• A and D are doubled, C and R remain unchanged• A and D remain unchanged,C is doubled and B is halved
Answer -- A and D remain unchanged,R is doubled and C is halved
• The maximum power That a 12 V DC source with an internal resistance of 2 ohm can supply to
a resistive load is• 72 W• 48 W• 24 W• 18 W
Answer -- 18W
• If the potential difference between points A (1,0,0) and B (2,0,0) is 10V, determine d for point C(d,0,0), when Vbc is 6 V in a uniform field
• 1 m• 2 m• 6 m• 5 m
Answer -- 5 m
• The credit of defining the following current is due to Maxwell• Conduction current• Drift current• Displacement current• Diffusion current
Answer -- Displacement current
• A Hall effect transducer is generally used for the measurement of• power• current• displacement• voltage
Answer -- displacement
• A digital linear displacement transducer normally uses• straight binary code• binary coded decimal• Gray code• hexadecimal code
Answer -- Gray code
• One of the following can act as an inverse transducer• Electrical resistance potentiometer• LVDT• Piezoelectric crystal• Capacitive transducer
Answer -- Piezoelectric crystal
• Two strain gauges are used to measure strain in a cantilever, one gauge is mounted on the top of the cantilever and the other is placed at the bottom. The two strain gauges form two arms of Wheatstone bridge. This bridge configuration is called
• a quarter bridge
• a half bridge• a full bridge• a null bridge
Answer -- a half bridge
• The following transducer is used for accurate and precise measurement of temperature• Thermistor• Thermocouple (Alumel / Chromel)• Semiconductor temperature sensor chip• Platinum.resistance thermometer
Answer -- Platinum.resistance thermometer
• Electrical voltage-based telemetering schemes used for short distances must necessarily have• low current level only• small signal power only• high signal to noise ratio• All of the above
Answer -- All of the above
• Electrical positional system telemetering uses for transmission of signal in• two wires only• two or three wires only• two or three or four wires only• two or three or four or even five wires
Answer -- two or three or four wires only
• During measurement of voltage and current in a load, ammeter and voltmeter are connected in series and across the load respectively. If ammeter and voltmeter positions are interchanged by mistake, then
• voltmeter will be damaged• ammeter will be damaged• both the meters will be damaged• both the meters will be safe
Answer -- ammeter will be damaged
• The ratio of the transverse electric field to the transverse magnetic field is called as• waveguide impedance• waveguide wavelength• phase velocity• Poynting vector
Answer -- waveguide impedance
• Consider a rectangular waveguide of internal dimensions 8 cm x 4 cm.Assuming an H10 mode of propagation,the critical wavelength would be
• 8 cm• 16 cm• 4 cm
• 32 cm
Answer -- 16 cm
• The ratio of the transverse electric field to the transverse magnetic field is called as• waveguide impedance• waveguide wavelength• phase velocity• Poynting vector
Answer -- waveguide impedance
• For the recording of very fast random signals, the most suitable instrument would be• dual-trace• sampling oscilloscope• real-time spectrum analyzer• scanning-type spectrum analyzer
Answer -- real-time spectrum analyzer
• To increase the range of a voltmeter• a low resistance in series is connected with the voltmeter• a low resistance in parallel is connected with the voltmeter• a high resistance in series is connected with the voltmeter• a high resistance in parallel is connected with the voltmeter
Answer -- a high resistance in series is connected with the voltmeter
• The following type of instrument can be used for measuring AC voltage of the highest frequency with reasonable accuracy
• Electrodynamometer• Moving iron• thermal-thermoelectric• Rectifier
Answer -- thermal-thermoelectric
• The null balance potentiometer measurement of voltage technique is not capable of measuring• DC voltage• AC voltage• voltage with higher accuracy and sensitivity as compared to deflection-type instrument• dynamic and transient voltage changes
Answer -- voltage with higher accuracy and sensitivity as compared to deflection-type instrument
• A d Arsonval meter of 100 ohm DC coil and 0-1 mA sensitivity gives full-scale reading of 10 A on using an external resistance of
• 100• 10• .01• .001
Answer -- .01
• Lissajous pattern shown in a double-beam cathode-ray oscilloscope screen for two sinusoidal voltages of equal magnitude and of the same frequency but of phase shift of 30°electrical is
• a circle• a straight line at 45° in the first and third quadrant• an ellipse in the first and third quadrant• an ellipse in the second and fourth quadrant
Answer --an ellipse in the first and third quadrant
• A Q-meter is supplied with an oscillator having a 500 mV output voltage. While testing an unknown inductor,the voltage across the variable capacitor of the Q-meter,measured by a digital voltmeter,is obtained as 10 V.The Q- factor of the inductor is
• 5• 10• 20• .05
Answer --20
• The following transducer(s) may employ strain gauge as a secondary transducer• Load cell only• Load cell and torquemeter only• Load cell, torquerneter and accelerometer only• Load cell, torquemeter, accelerometer and flowmeter
Answer --Load cell and torquemeter only
• In a digital frequency meter, the Schmitt trigger is used for• converting sinusoidal wave-forms into rectangular pulses• scaling of sinusoidal waveforms• providing timebase• triggering a start pulse
Answer --converting sinusoidal wave-forms into rectangular pulses
• Moving-coil permanent magnet instruments can be used for the measurement of• AC and DC• AC only• DC only• half-wave rectified DC
Answer -- DC only
• For controlling the vibration of the disc of an AC energy meter damping torque is produced by• eddy current• chemical effect• electrostatic effect• magnetic effect
Answer -- eddy current
• Analog inputs are converted to digital outputs using op-amps as comparators.Assuming a 5-bit digital output,the number of comparators required would be
• 32• 31• 64• 63
Answer -- 31
• A resistance is measured by a voltmeter-ammeter method using DC excitation and a voltmeter of very high resistance connected directly across the unknown resistance.If the voltmeter and ammeter are subject to maximum error of ±2.4% and ±1.0% respectively, then the magnitude of maximum error in the value of resistance obtained from the measurement is nearly
• 1.4%• 1.7%• 2.4%• 3.4%
Answer -- 3.4%
• The directivity of a λ/2 long wire antenna is• 1.5• 1.66• 2• 1.41
Answer -- 1.66
Statement (I):All substances except ferromagnetic materials which can form permanent magnets, exhibit magnetic effects.
Statement (11):Their magnetic effect is due to alignment of dipoles when subjected to an external electromagnetic field.
• a• b• c• d
Answer -- a
Statement (1):Concentration of acceptor atoms in the region between isolation islands in a monolithic integrated circuit will be much higher than in the p type substrate.
Statement (II):The higher density is provided to prevent the depletion region of the reverse-biased isolation to substrate junction from extending into the p+ type material.
• a• b• c
• d
Answer -- a
Statement(I):The gate of MOSFET is insulated from the body of FET by deposition of a very thin fragile layer of SiO2 over the substrate.
Statement(I1):The device is therefore called as an insulated gate Field-effect transistor(IGFET).
• a• b• c• d
Answer -- d
Statement (I):Z-transform approach is used to analyze the discrete lime systems and is also called as pulse transfer function approach.
Statement (II):The sampled signal is assumed to be a train of impulses whose strengths or areas are equal to the continuous time signal at the sampling instants.
• a• b• c• d
Answer -- c
Statement(1):Lossless network functions have only imaginary zeros and poles with only negative real parts.
Statement(II):Lossless network functions obey the separation property.
• a• b• c• d
Answer -- a
Statement (1):Resistance hygrometer is a good humidity transducer.
Statement (II):Resistance hygrometer has a sensing element and absorbs or gives up moisture till equilibrium is reached with ambient water vapour pressure.
• a• b• c
• d
Answer -- c
Statement (I):Dual-slope A/D converter is the most preferred A/D conversion approach in digital multimeters.
Statement (I1):Dual-slope A/ D converter provides high accuracy in A/D conversion, while at the same time suppressing the hum effect on the input signal.
• a• b• c• d
Answer -- a
Statement (1):RF voltage is measured by rectifying the alternating voltage first and then amplifying the resulting DC output.
Statement (11):Amplification of RF signals is itself a very difficult task.
• a• b• c• d
Answer -- c
Statement (I):Digital universal counter timer is used to measure time period and frequency of various circuits which are assembled together to form one complete block.
Statement (11):Digital counters use logic gates which are selected and controlled by a single front panel switch known as function switch which can be in either frequency or time-base mode.
• a• b• c• d
Answer -- a
• A bipolar junction transistor with forward current transfer ratio a = 0.98, when working in CE mode,provides current transfer ratio b as
• 98• .02• 49• .49
Answer -- 49
• A BJT is biased with a power supply of 12 V.For minimum heat dissipation,the drop across the transistor will
• 6 V• 9 V• 12 V• greater than 9 V but less than 12 V
Answer -- 6 V
• A transistor is said to be useful to be configured as an amplifier when its f is• Less than 0• Between 0 and 1• Between 1 and 50• > 50
Answer -- > 50
• In a transistor biased in the active region,thermal runway is due to• Base emitter. voltage Vbe which decreases with rise in temperature• Change in reverse collector saturation current due to-rise in temperature• Heating of the transistor• Changes in beta which increases with temperature
Answer -- Change in reverse collector saturation current due to-rise in temperature
• A change in the value of the emitter resistance R in a differential amplifier• Affects the difference mode gain Ad• Affects the common mode gain Ac• affects both Ad and Ac• does not affect both Ad and Ac
Answer -- Affects the common mode gain Ac
• An output signal of a power amplifier has amplitudes of 2.5V fundamental,0.25V second harmonic and 0.1V third harmonic.The total percentage harmonic distortion of the signal is
• 12.8%• 10.8%• 6.4%• 1.4%
Answer -- 10.8%
• For a full wave rectifier, with sinusoidal input and inductor as filter, ripple factor for maximum load current and minimum load current conditions are respectively
• 0.1and I• 0.1and 0.47• 0 and 0.47• 0 and 0.22
Answer -- 0 and 0.47
• For a transistor used as a switch, td is delay time, tr is rise time, to is storage time and tf is fall time. Then turn-on time tON and turn-off time tOFF are respectively
• (td + t8) and (tr + tf)• (td + tf) and (th + tr)• (tr + t8) and (td + tf)• (td + tr) and (t8 + t f)
Answer -- (td + tr) and (t8 + t f)
• Simplified form of the logic expression (A + ‾B + C) (A +‾B +‾C) (A + B + C) a.‾AB+‾Cb.A + ‾B Cc.Ad.AB+‾C
• a• b• c• d
Answer -- b
• Binary data is being represented in size of byte , and in 2's complement form.The number of 0's present in representation of (- 127)decimal is
• 8• 7• 6• 5
Answer -- 6
• The figure of merit of a logic family is given by• Gain bandwidth product• (propagation delay time)*(power dissipation)• (Fan-out) x (Propagation delay time)• (Noise-margin) x (Power dissipation)
Answer -- (propagation delay time)*(power dissipation)
• In locations where the humidity is low IC based on one of the following technologies should be handled only after grounds the body.The technology is
• TTL• CMOS• DTL• XFT
Answer -- DTL
• Assuming that only logic inputs X and Y are available and their complements are not available,the minimum number of two-input NAND gates required to implement X Θ Y would be
• 2• 3• 4• 5
Answer --4
• The minimum number of NAND gates required to implement A + A‾B + A‾BC is equal to• 1• 4• 7
Answer --
• The type of device used to interface a parallel data format with external equipment's serial format is
• Key matrix• UART• Memory chip• Serial-in, parallel-out
Answer -- UART
• A bistable multi-vibrator that functions as a voltage comparator with hysteresis is called• T flip-flop• D flip-flop• J-K flip-flop• Schmitt trigger
Answer -- Schmitt trigger
• A pulse train with a frequency of 1 MHz is counted using a mod-1024 ripple counter built with J-K flip-flops: For proper operation of the counter the maximum permissible propagation delay per flip-flop stage is
• 100 ns• 50 ns• 20 ns• 10 ns
Answer -- 100 ns
• The highest speed counter is• Asynchronous counter• Synchronous counter• Ripple counter• Ring counter
Answer -- Ring counter
• An analog voltage of 3.41 V is converted into 8-bit digital form by an A/D converter with a reference voltage of 5 V. The digital output is
• 1001 1001• 1111 0001• 1011 0111• 1010 1110
Answer -- 1010 1110
• In which of the following types of A/D converter does the conversion time almost double for
every bit added to the device ?• Counter type A/D converter• Tracking type A/D converter• Single-slope integrating type A/D converter• Successive approximation type A/D converter
Answer -- Counter type A/D converter
• If both inputs of S-R NAND latch are low, the output will be• Unpredictable• Toggle• Reset• Remain same
Answer -- Remain same
• A 10-bit DAC provides an analog output which has a maximum value of 10.23 volts.Resolution of the DAC is
• 10 mV• 15 mV• 20 mV• 40 mV
Answer -- 10 mV
• Consider the following statements regarding registers and latches : 1.Registers are temporary storage devices,whereas latches are not 2.A latch employs cross-coupled feedback connections3.A register stores a binary word,whereas a latch does not. The correct statements is/are
• 1• 2• 1 and 3• 2 and 3
Answer -- 2 and 3
• A 12-bit ADC is operating with a 1 μs clock period and total conversion time is seen to 14 μs. The ADC must be of
• Flash type• Counting type• Integrating type• Successive approximation type
Answer -- Successive approximation type
• The type of system which is used for determination of static error constants is determined from the number of
• Zeros at origin for open loop transfer function• Poles at origin for open loop transfer function• Zeros at origin for closed loop transfer function• Poles at origin for closed loop transfer function
Answer -- Poles at origin for open loop transfer function
• The crystal frequency of 8085 microprocessor is 6 MHz.The time required to execute instruction XTHL over this microprocessor is
• 5.33 microsec• 10.67 microsec• 4.33 microsec• 8.67 microsec
Answer -- 5.33 microsec
• In 8085 microprocessor, after the execution of RST 5 instruction, the program control shifts to• 0030 H• 0005 H• 0028 H• 0024 H
Answer -- 0028 H
• Consider the following 8085 interrupts 1.TRAP2.INTR3.RST 64.RST 7.55.RST 0 .The software interrupts are(a)1 and 3 only(b)2 and 5 only(c)3 and 5 only(d)1,2, 3,4 and 5
• a• b• c• d
Answer -- c
• The following register holds the instruction before it goes to the decoder• Control register• Accumulator• Address register• Data register
Answer -- Control register
• Among memory types, the abbreviation MPDRAM stands for• Multiport Dynamic Random Access Memory• Multipoint Dynamic Random Access Memory• Multipoint Disk Random Access Memory• Multiport Dimensional Random Access Memory
Answer -- Multiport Dynamic Random Access Memory
• A virtual memory system has an address space of 8 k words, a memory space of 4 k words and page and block sizes of 1 k words.The number of page faults using LRU policy,for following page references is 10246215700
• 5• 7• 9• 10
Answer -- 9
• The access time of a cache memory is 100 ns and that of main memory is 1 ms. 80% of the memory requests are for read and others are for write. Hit ratio for read only accesses is 0.9. A write through procedure is used. The average access time of the system for both read and write requests is
• 200 ns• 360 ns• 720 ns• 1100 ns
Answer -- 720 ns
• Consider the following statements for a DRAM 1.Bit is stored as a charge2.It is made of MOS transistors.3.Speed of DRAM is faster than processors4.Each memory cell requires six transistors. Which of these statements are correct ?(a)1 and 2 only(b)2 and 3 only(c)3 and 4 only(d)1,2, 3 and 4
• a• b• c• d
Answer -- a
• A memory system has a total of 8 memory chips each with 12 address lines and 4 data lines. The size of the memory system is
• 16 k bytes• 32 k bytes• 48 k bytes• 64 k bytes
Answer -- 16 k bytes
• In a microprocessor, the service routine for a certain interrupt starts from a fixed location of memory which cannot be externally set, but the interrupt can be delayed or rejected. Such an interrupt is
• Non-maskable and non-vectored• Maskable and non-vectored• Non-maskable and vectored• Maskable and vectored
Answer -- Maskable and vectored
• While executing a program,8085 microprocessor completes fetching of instruction JMP205 stored at address 2057 H. The contents of the program counter after fetching the instruction would be
• 2050 H• 2057 H• 205A H• 2051 H
Answer -- 2050 H
• The action performed by the following instruction of 8086: mov [1234h], AX• Move contents of memory location 1234h to register AX• Move the contents of register AX to memory offset 1234h• Add contents at 1234h to register AX• Add contents of 1234h and AX and store the result in 1234h
Answer -- Move the contents of register AX to memory offset 1234h
• For 8086 microprocessor, the jump distance in bytes for short jump range is• Forward 255 and Backward 256• Forward 127 and Backward 128• Forward 31 and Backward 32• Forward 15 and Backward 16
Answer -- Forward 127 and Backward 128
• An Intel8085 processor is executing the program given below MVI A, 10HMVl B, 1OH BACK: NOPADDBRLCJNC BACKHLT The number of times that the operation NOP will be executed is
• 1• 2• 3• 4
Answer -- 3
• Following program finds absolute value of N : MVI A,NORA AJM ONEOUT 01HHLT ONE :PQOUT 01H
HLT The instructions of P and Q must be
• CMA and ADI OH• CMC and ADI OH• INR A and CMC• INR A and CMA
Answer -- CMA and ADI OH
• A small code of 8085as given below, is executed MVI A, 7FHORA ACPI A2H. The contents of the accumulator and flags after execution are
• A=DD,S=I,Z=O,CY=O• A=7F,S=1,Z=0,CY=1• A=DD,S=O,Z=I,CY=O• A=7F,S=O,Z=1,CY=1
Answer -- A=7F,S=1,Z=0,CY=1
• For the 8085 assembly language program given below, the content of the accumulator after the execution of the program is 3000 MVI A, 45113002 MOV B, A3003 STC3004 CMC3005 RAR3096 XRA B3007 HLT
• 00 H• 45 H• 67 H• E7 H
Answer -- 67H
• The 8254 Programmable Interval Timer is set to work in MODE 5. The following would best describe its function
• Software triggered strobe• Hardware triggered strobe• Square wave generator• Interrupt on terminal count
Answer -- Hardware triggered strobe
• To configure port A and port B as output ports,port C not being used in the 8155 programmable interface, the control word should have the value
• 0311• 01H• 02H• 6011
Answer -- 0311
• The 8085 microprocessor instructions with required number of T states are given below.Which pair is correctly matched ?
• STAX : 8 T-states• SPHL :6 T-states• SIM :7 T-states• STA :12 T-states
Answer -- SPHL :6 T-states
• In communication systems,noise due to quantization error is• linear and signal dependent• Non-linear and signal dependent• Linear and signal independent at low frequencies only• Non-linear and signal dependent at low frequencies only
Answer -- linear and signal dependent
• For an earth station transmitter, with an antenna output power of 40 dBW (10,000 W), a back-off loss of 3 dB a total branching and feeder loss of 3 dB and transmit antenna gain of 4 dB the effective isotropic radiated power (EIRP) will be
• 38MW• 40 dBW• 36 dBW• 47 dBW
Answer -- 38MW
• A coherent binary phase-shift-keyed (BPSK) transmitter operates at a bit rate of 20 Mbps. For a probability of error P(e) of 10 and given carrier-to-noise (C/N) density ratio of 8.8dB, determine energy of bit-to-noise (Eb/NO) density ratio for a receiver bandwidth 7 equal to the minimum double-sided Nyquist bandwidth.
• 23 dB• 2.3 dB• 8.8 dB• 0.88 dB
Answer -- 0.88 dB
• An elliptically (arbitrarily) polarized wave can be broken up into• Two circularly polarized components rotating in same direction• Two circularly polarized components rotating in opposite directions• Two stationary circularly polarized components• None of these
Answer -- None of these
• Klystron operation is based on the principle of• velocity modulation• Amplitude modulation• Frequency modulation• Phase modulation
Answer -- velocity modulation
• The following is not an application of varactor diode• parametric amplifier• Frequency tuner• Voltage controlled oscillator• Phase shifter
Answer -- Phase shifter
• The following quantity is not required in the calculation of Q of a cavity resonator• Energy stored• Power dissipated• Loss in radiation• Dimensions of the cavity
Answer --Loss in radiation
• When electromagnetic waves are propagated in a waveguide• They travel along the walls of waveguide• They travel through the dielectric without touching the was• They are reflected from the walls but do not travel along the walls• None of these
Answer --They are reflected from the walls but do not travel along the walls
• Slotted line with tunable probe is not used to measure• VSWR• Wavelength• Power• impedance
Answer -- Power
• In a microwave magic-T, E plane and H plane are• In phase• Out of phase• Isolated• 90 degree out of phase
Answer -- Isolated
• Baratters and bolometers are used for measurement of• VSWR• Transmission losses• microwave power• Frequency
Answer -- microwave power
• Magnetic properties of ferrites result mainly from• Polarization of electromagnetic waves• Dielectric behaviour of ferrite
• Magnetic dipole moment associated with the electron spin• External magnetic fields
Answer -- Magnetic dipole moment associated with the electron spin
• An 8085 microprocessor executes the following instructions :Two numbers are represented in signed 2's complement form asP=1110110 and Q=11100110If Q is subtracted from P, the value obtained in signed 2's complement form is
• 10000111• 00000111• 11111001• 011111001
Answer -- 00000111
• If (11X1Y)8 = (12C9)16 then the values X and Y are• 5 and 1• 5 and 7• 7 and 5• 1 and 5
Answer -- 5 and 1
• A binary tree T has n leaf nodes.The number of nodes of degree 2 in T is• log2N• n-1• n• 2 to power n
Answer -- log2N
• The data structure needed to convert infix notation to prefix notation is• Queue• Stack• Tree• Graph
Answer -- Stack
• In case the code is position dependent, the most suitable addressing mode is• Direct mode• Indirect mode• Relative mode• Indexed mode
Answer --Relative mode
• If root loci plots of a particular control system do not intersect the imaginary axis at an point, then the gain margin of the system will be
• Zero• 0.707• 1.0
• infinite
Answer -- infinite
• The characteristic equation of a particular system is given by s3 + 2s2 + 6s + 12 = 0. The damping ratio will be
• between 0 and 1• 1• greater than 1
Answer -- 1
• For a type 1 system,the low frequency asymptote of its Bode plot will have a slope of• 0 dB/decade• 6 dB/decade• 20 dB/decade• -20 dB/decade
Answer -- -20 dB/decade
• The gain cross-over frequency and phase margin of the transfer function (1/s(s+1)) are• 1 rad/s and 45°• 2 rad/s and 45°• 2 rad/s and 135°• 1 rad/s and 135°
Answer -- 1 rad/s and 45°
• For a unity feedback control system, if its open-loop transfer function is given byG(s) H(s) =(10/(s+5) to the power 3) then its gain margin will
• 20 db• 40 db• 60 db• 80 db
Answer -- 40 db
• All the constant - N loci in G-plane intersect the real axis in points• - 1 and origin• - 0.5 and + 0.5• - 1 and + 1• Origin and + 1
Answer -- - 1 and origin
• A third order system is approximated to an equivalent second order systems The rise time of this approximated system will be
• Same as the original system for any input• Smaller than the original system for any input• Larger than the original system for any input• Smaller or larger depending on the type of input
Answer --Smaller than the original system for any input
• Considering the filtering property, the lead compensator and lag compensator are categorized respectively as
• Low pass and high pass filters• high pass and low pass filters• High pass and high pass filters• Low pass and low pass filters
Answer -- high pass and low pass filters
• The necessary conditions for poles and zeros of the transfer function of a bridge-T network containing,only resistors and capacitor and used as a compensator are
• All the poles and zeros must be imaginary• Poles and zeros both can be complex• Poles can be complex but zeros must be real• Zeros can be complex but poles must be real
Answer -- Zeros can be complex but poles must be real
• A liquid level controller linearly converts a displacement of 2 m to 3 in into 4-20 mA control signal. A relay serves as two position controller to open and close an inlet valve.Relay closes at 12 mA and opens at 10 mA.The hysteresis zone is
• 0.1 m• 0.125 m• 0.15 m• 0.2m
Answer -- 0.125 m
• A proportional integral results in which of the following ?• Improves the transient response without affecting steady state response• Improves the steady state response without affecting transient response• Improves both transient response and steady state-response• Improves the steady state response while marginally affecting transient response, for
well designed control
Answer -- Improves the steady state response while marginally affecting transient response, for well designed control
• The effect of integral controller on the steady state error (ess) and on the relative stability (Rs) of the system are
• Both are increased• ess is increased but Rs is reduced• ess is reduced but Rs is increased• Both are reduced
Answer -- Both are reduced
• The average information associated with an extremely likely message is zero. What is the average information associated with an extremely unlikely message ?
• Zero• Infinity• Depends on total number of messages
• Depends on speed of transmission of the message
Answer -- Infinity
• The spectral density and auto correlation function of white noise is• Delta and uniform• uniform and delta• Gaussian and uniform• Gaussian and delta
Answer -- uniform and delta
• The threshold effect in demodulators is• The rapid fall of output SNR when the input SNR fails below a particular value• Exhibited by all the demodulators when the input SNR is low• Exhibited by all AM suppressed carrier coherent demodulators• Exhibited by correlation receivers
Answer -- The rapid fall of output SNR when the input SNR fails below a particular value
Directions : Each of the next thirteen (13) items consists of two statements, one labelled as the Statement (1) and the other as Statement (11).Youare to examine these two statements carefully and select the answers to these items using the codes given below :
Codes :(a)Both Statement (I) and Statement (II) are individually true and Statement (II)is the correct explanation of Statement (I)(b)Both Statement (I) and Statement (II) are individually true but Statement (11)is not the correct explanation of Statement (I)(c)Statement (I) is true but Statement (II) is false(d)Statement (I) is false but Statement III) is true
Statement (1) :In a transistor designed to be used. for power amplification,the collector size is largest relative to the emitter and base.Statement (II) : The collector is connected to the body of the transistor and hence to a heat sink for heat dissipation to be effective.
• a• b• c• d
Answer -- a
Statement (I) : The carry look-ahead adder is a fast adder.Statement (11) : The carry look-ahead adder generates the carry and the sum digits directly.
• a• b• c• d
Answer -- a
Statement (1) : Root loci are symmetrical with respect to real axis of the s-plane.Statement (11) : Root loci are normally symmetrical with respect to the perpendicular axis of symmetry of the pole-zero combination of the loop transfer function.
• a• b• c• d
Answer -- a
Directions : Each of the next thirteen (10) items consists of two statements, one labelled as the Statement (1) and the other as Statement (11).You are to examine these two statements carefully and select the answers to these items using the codes given below :
Codes :
(a)Both Statement (I) and Statement (II) are individually true and Statement (II)is the correct explanation of Statement (I)
(b)Both Statement (I) and Statement (II) are individually true but Statement (11)is not the correct explanation of Statement (I)
(c)Statement (I) is true but Statement (II) is false
(d)Statement (I) is false but Statement III) is true
Statement (1) : Nyquist criterion is a powerful tool to determine stability of a closed loop system using open loop transfer function.Statement (11) : Nyquist criterion relates the locations of poles and zeros of the closed loop transfer function.
• a• b• c• d
Answer -- b
Statement (1) : A second order system subjected to a unit impulse oscillates at its natural frequency.Statement (11):Impulse input contains frequencies from - infinity to + infinity.
• a• b• c• d
Answer -- a
Statement (1) : All the systems which exhibit overshoot in transient response will also exhibit resonance peak in frequency response.Statement (II) : A large resonance peak in frequency response corresponds to a large overshoot in transient response.
• a• b
• c• d
Answer -- d
Statement (1) : In a prototype second order system the rise time tr and bandwidth are inversely proportional.Statement (II) : Increasing wn increases bandwidth while tr reduces.
• a• b• c• d
Answer -- b
Statement (I) : The phase angle plot in Bode diagram is not affected by the variation in open loop gain of the system.Statement (11) : The variation in gain of the system has no effect on the phase margin.
• a• b• c• d
Answer -- c
Statement (1) : FM spectrum consists of a carrier and an infinite number of side band components.Statement (II) : FM signals are used only in TV transmission to ensure better picture quality.
• a• b• c• d
Answer -- c
Statement (1) : In the two body system consisting of the earth and a satellite, centre of mass always coincides with centre of the earth.Statement (11) : Mass of earth is much greater than mass of satellite.
• a• b• c• d
Answer -- a
Statement(I):Gunn effect device is a slice made from n-doped GaAs and provides negative resistance characteristics.Statement (II) : GaAs has an empty energy band higher in energy than the filled or partly filled bands.
• a• b• c
• d
Answer -- c
Statement (1): Power output of the lowest mode in a reflex klystron is maximum.Statement (II) : Lower modes occur at higher repeller voltages where the acceleration of bunched electrons on return is maximum
• a• b• c• d
Answer -- a
Statement (I) : The DMA technique is more efficient than the Interrupt-driven technique for high volume I/O data transfer.Statement (I) : The DMA technique does not make use of the Interrupt mechanism.
• a• b• c• d
Answer -- b