NTPC PREVIOUS PAPERS

Technical Paper :

1. Given four unit-circle plots identify the one corresponding to a bandpass filter.

2. A 4 kHz signal is sampled at thrice the Nyquist rate and sent through a channel
with error ≤1%. Calc the bandwidth of the channel.

3. Given a two port network in the form of a T find o/p admittance in terms of y-
parameters.

4. Connect two 1Ω resistors in series, then connect two 1H inductors across one of the resistors such that the ckt looks like a 1Ω resistor in series with a Π-section of
a resistor and two inductors. With the series resistance on the i/p side, calc the
transfer function of this ckt

5. Inverse laplace transform of 1/s2[d/ds(e-3s/s)]

6. Lower useful input limit of a transducer is determined by…

7. Air-cored inductors are used for low frequency/high frequency/equal
frequency operations.

8. Given 4 pole-zero plots identify which one corresponds to the driving point
impedance of a series resonant ckt.

9. Expression for δ(n): u(n)-u(n-1)/ u(n-1)-u(n+1)/ u(n)+u(n+1)/...

10. The sequence (2,3,4,3) is circularly even/circularly odd/circularly zero/both
circularly even and odd.

11. Z-transform of 3n u(n).

12. Match the following with their characteristics: LED/LCD/nixie tube/optical
fibre.

13. Numerical on a photodiode: to calculate the responsivity/sensitivity when a
specified no of incident photons cause a specified no of electron generation.

14. Given an op-amp ckt obtain an expression for o/p voltage.

15. No. of encirclements made about the origin of the nyquist plot of the open
loop TF:1/[(s-1)(s+2)(s+3)].

16. For a radioactive sample which decays to 12.5% of its initial value in x days,
the half life is given by____

17. For a repeater in a PCM cable identify the correct sequence of actions amongst
threshold/equalization/etc.

18. O/P of a delta modulator when a ramp input is fed to it.

19. Steady state error with ramp i/p for a type-0 system.

20. Creeping occurs in energy meters bcoz….

21. Ultrasonic method of flow measurement cannot be used in liquids with air bubbles/has less attenuation in air compared to liquid-identify the false
statement (if any) among these.

22. Major cause of losses in a fibre optic cable: dispersion/total internal
refraction/presence of core and cladding/…

23. Which layer in the OSI model is concerned with printer buffering,etc:
network/session/transport/…

24. Given some function F(jω) calc its inverse CTFT.

25. Relation between laplace and z-transform: s=z/ s=ln z/ s=( ln z/T) /…

26. Maxm and minm probability error among ASK,PSK,FSK,DPSK etc

27. Which of the following is a non linear modulation scheme: PAM/QAM/PCM/
…

28. Match the following functions: e-t , e-t + et, sin(πt) with causal and stable
system, causal and unstable system, etc.

29. Given a ckt with a 50 Ω resistor in series between two voltage sources of 10 V
and 5 V magnitude calc power delivered by 5 V source.

30. Laplace transform of e-3tu(t)+e2tu(-t).

31. Which photodetector has output affected by own intrinsic noise:
PN/APD/PIN/all.

32. AC signal conditioning is used for inductive and
capacitive/resistive/piezoelectric transducers/all of the above.

33. When I mode is added to proportional control system stability increases/
decreases/ steady state performance deteriorates/damping increases.

34. Reset control is another name for integral/derivative/proportional/….
Control.

35. Time response of system having transfer function 625/(s2+25) will be of the
form…

36. Given some transfer function calc the peak response time.

37. The nyquist sampling rate of the function [sin(at)/t]2 will be…

38. The feedback topology that results in increased i/p and o/p impedance is
current series/voltage series/current shunt voltage shunt.

39. Numerical on cardiac output calculation given heart rate and volume per
beat.

40. In an ECG instrumentation amplifier the differential gain is provided by 1st
stage/2nd stage/mismatched resistors/output stage.

41. Repeat ques 40 above for the classic 3-op amp instrum amplifier.

42. EMG signals are of the order of mV/V/μV/…

43. Computer assisted tomography is used for…

44. Numerical on electrostatic instrument, to calculate deflection given spring
constant, torque etc.

45. To prevent loading of a ckt i/p impedance of a CRO should bee
high/low/inductive/capacitive.

46. Addition of a zero to a 2nd order underdamped system results in
increase/decrease of rise time and increase/decrease of peak overshoot.

47. For PI ctrl we obtain improved bandwidth/improved steady state
performance/ worsened steady state performance/…

48. SNR of normal AM system is comparable/3 dB lower/3 dB higher/6 dB lower
over DSB-SC and SSB system.

49. Which is an effective measure of the noise related performance of an
amplifier: SNR/noise ratio/thermal noise/shot noise.

50. Given baseband signal freq and carrier freq calc which of the freq given will
not be present for conventional AM.

51. Distinction between FM and PM at high frequencies.

52. Which of these has the least propagation delay RTL/ECL/I2L/CMOS.

53 Switching speed of CMOS is affected/unaffected by changes in supply voltage.

54. Which of these provides a measure of heart rate P/QRS complex/T/none of
these.

55. Given a ckt of a logarithmic amplifier you had to identify what ckt was it.

56. JFET can operate in depletion/enhancement/both/none of the above modes.57. When a BJT operates in saturation the junctions are fwd biased/reverse
biased/…

58. BIBO stability criterion implies that poles are within/outside/on the unit
circle.

59. For faithful amplification of low amplitude signals the cut-
off/active/saturation regions of a transistor is used.

60. Lissajous pattern of a signal rotates 36 times per minute. if the oscillator
frequency is 560 kHz then the unknown freq is…

61. % resolution of a 10 bit ADC.

62. To obtain 10 mV resolution on 5 V range how many bit DAC is to be used..

63. Why is LCD preferred to LED.

64. How will 0.6973 be displayed on 10 V range of a 4 ½ digit multimeter.

65. Which of the following cannot be used for an automatic feedback temp ctrl
system thermocouple/thermometer/thermistor/IC sensor.

66. Y(n)=X(-n+3) is an example of a linear/non linear and shift variant/invariant
system.

67. The falling body method is used to determine viscosity/humidity/….

68. Which of these methods of viscosity measurement gives greatest accuracy
falling body method/rotating cylinder method/both/…

69. Some question on gas chromatography

70. A device having a rotor with 3 Y-connected coils and a stator is likely to be a
synchro/RVDT/control transformer/…

71. In a twisted ring counter the initial count is 1000. after the 4th clock pulse its
state will be….

72. A 240 kHz signal is given into a 3 bit binary ripple counter. The lowest o/p
freq obtainable is….

73. For parity bit checking which of the following gates can be used
XOR/NAND/OR/XNOR.

74. Why is a BJT called so..75. Identify the expression for gauge factor of a strain gauge among the given
options.

76. In a semiconductor strain gauge as tensile strain is applied what changes take
place in the n and p areas..

77. How does a radioactive level gauging system work…

78. A capacitive transducer measuring level works on the principle of change in
distance between plates/change in dielectric strength/…

79. For maximum power transfer in an AC circuit the condition to be satisfied is
ZL+ZS=0/XL+XS=0/none of these/….where l and s refers to load and source
respectively.

80. Find the transfer function from a block diagram.

81. Synchronous ctrs are preferred to asynchronous ctrs bcoz they are
faster/glitches at the output can be avoided/both/none of these.

82. The lissajous figure formed on an oscilloscope looks like the English figure of
8. if the vertical channel input is 1 kHz the horizontal input freq is….

83. IE=IC for a transistor in saturation/cutoff/active/both saturation and active
regions.

84. Reproducibility of measurements is called accuracy/precision/linearity/none
of these.

85. Which of these is not strictly a static characteristic
accuracy/precision/tolerance/linearity.

86. The shunt coil in a Q meter has resistance of the order of mΩ/Ω/kΩ/..

87. For measuring inductance of high Q coils the bridge used is Maxwell-
wien/Schering/…

88. Which of these measures inductance in terms of capacitance Maxwell and
hay/Maxwell and Schering/hay and Schering/…

89. In a flip-flop with preset and clear inputs both are applied
simultaneously/clear is cleared when preset is applied/preset is cleared when
clear is applied/….

90. What happens when the RET instruction is encountered by 808591. A 1024*8 memory chip needs how many address lines…

92. What happens when the PUSH instruction is encountered by 8051.

93. In FM relation between no of sidebands w.r.t. modulating freq

94. Numerical on DPSK.

95. A multiplexer accepts input data and provides one output all the time/one
output at a time/many outputs at a time/many outputs all the time.

96. Pulse modulation is essentially a process of multiplexing/….

97. Wave shape is altered by clipper/clamper/voltage doubler/amplifier.

98. 4 signals of frequencies 100,100,200 and 400 Hz are sampled at nyquist rate
and sent through TDM on a channel.the bandwidth of the channel is…

99. Superposition can be applied to a ckt with initial conditions/non-linear ckt/…

100. Kelvin’s double bridge is used for the measurement of…

101. Which of these is not an active transducer thermocouple/solar
cell/RTD/none of these.

102. Oscillator using positive feedback has gain of 0/∞/undefined value/…

103. Wien bridge oscillator should initially have closed loop gain >3/<3/=3/…

104. Some question on gain margin and phase shift of a system.

105. Fourier series expansion of even function has sine terms only/cosine terms
only/no odd harmonics/…

106. Full wave rectifier gives clean dc o/p/dc o/p with small ripple/positive half
and inverted negative half of i/p as o/p.

107. Which of these values of ζ gives damped oscillations: 0/1/1.6/0.6

108. For a transformer of ratio 1:a and excited by a source V with impedances Z1
and Z2 on the primary and secondary side value of a for maxm power transfer
should be..

109. Fourier transform of cos(ω0t) is…

110. At t=0 the step response of a 1st order system is….111. 555 can be used as a monostable/astable/freq dividing ckt/all of these.

112. In a PT when the secondary is open ckted with the primary excited what will
happen.

113. If a system is marginally stable then the nature of oscillations will be…

114. Linear encoders mostly use straight binary/BCD/gray code.

115. For an accelerometer working in displacement mode the ratio of forcing freq
to natural freq should be…..

It may Contain questions with options like Both a) and b) . While solving this
type of Question we may get some difficulty, but practicing more we can
overcome this difficulty. All the best and do more Practice.

NTPC PAPER : 2007 AT NEW DELHI :

APTITUDE SECTION :

For this section no special attention is required only rs aggarwal is enough and it also has easy
level of English section.

TECHNICAL SECTION :

For this section u have to b good in the basics. No hard question were asked but u
should b careful about your time . It has also some part of very basic general
knowledge. The questions were from following topics

10-12 Questions about microprocessor(8085)

3 Questions about RS232 standard

7-10 Questions of GK

4-6 Questions on opamp

10-15 Questions on Digital Communications

2-5 Questions on microwaves

15-20 Questions on Analog Devices

20-23 Questions on Digital Electronics (flip flops,gates,mux,no system etc)

1 Questions on ISO OSI Model

5-8 Questions on Control System

10-12 Questions on Signals and their Processing

AND SOME QUESTIONS ON PASSAGES & LIKE

1. Passage
2. Word meaning based (antonym and synonyms) fetter, fester, lucid, anomaly, elucidate etc
3. Word analogy based
4. What is a tunnel diode
5. What is a Zener diode
6. Effect of + and – feedback on stability7. Composition of gobar gas
8. Function of differential in the vehicle
9. Function of stack register
10. Fun of instruction pointer
11. Fun of rst6.5,7.5
12. Wht is an interrupt
13. Output vtg calc on op amp
14. How a pulse train can b generated using registers
15. Conversion of oct to hex,hex to binary
16. Fun of quantizer in pcm
17. Why fm is less prone to noise
18. Fun of limiter in detection of FM
19. What is envelop detector
20. Phase shift of 1/s^2
21. Signal limited to 1000 hz sampled at nyquist rate. quantizer has 128 level .calculate the bit rate of the system.
22. 1.5 V battery supply same power to R1 and R2 separately(R1>R2).calc the internal
resistance of battery
23. A wire is cut in two halves. one half is again stretched to th twice of length .calc the resistance.

Ntpc sylaabus for E&Tc

Syllabus for Control & Instrumentation

1. Basics of Circuits and Measurement Systems:

Kirchoff's laws, mesh and nodal Analysis. Circuit theorems. One-port and two-port Network Functions. Static and dynamic characteristics of Measurement Systems. Error and uncertainty analysis. Statistical analysis of data and curve fitting.

2. Transducers, Mechanical Measurement and Industrial Instrumentation:

Resistive, Capacitive, Inductive and piezoelectric transducers and their signal conditioning. Measurement of displacement, velocity and acceleration (translational and rotational), force, vibration and shock. Measurement of pressure, flow, temperature and liquid level. Measurement of pH, conductivity, humidity, hydrazine, silica, dissolved O2. Units and standards of measurement.

3. Analog Electronics:

Characteristics of diode, BJT, JFET and MOSFET. Diode circuits. Transistors at low and high frequencies, Amplifiers, single and multi-stage. Feedback amplifiers. Operational amplifiers, characteristics and circuit configurations. Instrumentation amplifier. Precision rectifier. V-to-I and I-to-V converter. Op-Amp based active filters. Oscillators and signal generators. Voltage stabiliser and regulator circuits. Inverter and converter circuits.

4. Digital Electronics:

Combinational logic circuits, minimization of Boolean functions. IC families, TTL, MOS and CMOS. Arithmetic circuits. Comparators, Schmitt trigger, timers and mono-stable multi-vibrator. Sequential circuits, flip-flops, counters, shift registers. Multiplexer, S/H circuit. Analog-to-Digital and Digital-to-Analog converters. Basics of number system. Microprocessor applications, memory and input-output interfacing. Microcontrollers.

5. Electrical and Electronic Measurements:

Bridges and potentiometers, measurement of R,L and C. Measurements of voltage, current, power, power factor and energy. A.C & D.C current probes. Extension of instrument ranges. Q-meter and waveform analyzer. Digital voltmeter and multi-meter. Time, phase and frequency measurements. Cathode ray oscilloscope. Instrument Transformer.

6. Control Systems and Process Control:

Feedback principles. Signal flow graphs. Transient Response, steady-state-errors. Routh and Nyquist criteria. Bode plot, root loci. Time delay systems. Phase and gain margin. State space representation of systems. Mechanical, hydraulic and pneumatic system components. Synchro pair, servo and step motors. On-off, cascade, P, P-I, P-I-D, feed forward and derivative controller, Fuzzy controllers. Multi-state variable and Adaptative controls. System modeling, Digital controls, Distributed digital controls, control loops based on computers.
7. Analytical, Optical and Biomedical Instrumentation:

Mass spectrometry. UV, visible and IR spectrometry. X-ray and nuclear radiation measurements. Optical sources and detectors, LED, laser, Photo-diode, photo-resistor and their characteristics. Interferometers, applications in metrology.

8. Signals and Systems:

Definitions and properties of Laplace transform, continuous-time and discrete-time Fourier series, continuous-time and discrete-time Fourier Transform, DFT and FFT, z-transform. Sampling theorem. Linear Time-Invariant (LTI) Systems: definitions and properties; causality, stability, impulse response, convolution, poles and zeros, parallel and cascade structure, frequency response, group delay, phase delay. Signal transmission through LTI systems.

9. Communications:

Random signals and noise: probability, random variables, probability density function, autocorrelation, power spectral density. Analog communication systems: amplitude and angle modulation and demodulation systems, spectral analysis of these operations, superheterodyne receivers; elements of hardware, realizations of analog communication systems; signal-to-noise ratio (SNR) calculations for amplitude modulation (AM) and frequency modulation (FM) for low noise conditions. Fundamentals of information theory and channel capacity theorem. Digital communication systems: pulse code modulation (PCM), differential pulse code modulation (DPCM), digital modulation schemes: amplitude, phase and frequency shift keying schemes (ASK, PSK, FSK), matched filter receivers, bandwidth consideration and probability of error calculations for these schemes. Basics of TDMA, FDMA and CDMA and GSM. Basic Network topology and Net work hard wares. LAN / WAN configurations. UTP and OFC Links and components. Serial and parallel communication, Shielding and grounding. IEEE standards and broadband.