NTPC PAPER - 04 MAY 2016 - KOLKATA
Hi Friends
Technical (control and instrumentation):
1. Expression for d(n): u(n)-u(n-1)/ u(n-1)-u(n+1)/ u(n)+u(n+1)/...
2. Numerical on a photodiode: to calculate the responsivity/sensitivity when
a specified no of incident photons cause a specified no of electron
generation.
3. For a radioactive sample which decays to 12.5% of its initial value in x
days, the half life is given by..
4. Connect two 1o resistors in series, then connect two 1h inductors across
one of the resistors such that the ckt looks like a 1o resistor in series
with a ?-section of a resistor and two inductors. With the series resistance
on the I/p side, calc the transfer function of this ckt
5. Ac signal conditioning is used for inductive and
capacitive/resistive/piezoelectric transducers/all of the above.
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. Given four unit-circle plots identify the one corresponding to a bandpass
filter.
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. 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.
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. Given a two port network in the form of a t find o/p admittance in terms
of y-parameters.
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(j?) 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(pt) with causal and
stable system, causal and unstable system, etc.
29. Given a ckt with a 50 o 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. Inverse laplace transform of 1/s2[d/ds(e-3s/s)]
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 resp.
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 mo/o/ko/..
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 8085
91. 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 0/8/undefined value/..
103. Wien bridge oscillator should initially have closed loop gain
>3/<3 br="">
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 ? 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(?0t) 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....
That's all I can remember! One fact which I wish to mention is that many
questions contained options which were repeated, e.g. Both a) and b) were 5.
It was difficult making a choice in these cases.
Aptitude (70 ques):
Most of the questions were straight forward. There were questions involving
profit and loss, ratio-proportion, di from pie-charts, one rc passage and
other questions from verbal. The ones involving verbal were quite confusing,
as none of the options seemed to fit the question,e.g there were some
questions in which you had to find the word farthest in meaning to a given
word. The word given was judicious, and the options were illegal, obscure,
case and some other. The same was the case with the other four questions of
this sort.
Overall it was an ok sort of paper, though the negligible weightage given to
instrumentation related questions was somewhat surprising.
Hi Friends
Technical (control and instrumentation):
1. Expression for d(n): u(n)-u(n-1)/ u(n-1)-u(n+1)/ u(n)+u(n+1)/...
2. Numerical on a photodiode: to calculate the responsivity/sensitivity when
a specified no of incident photons cause a specified no of electron
generation.
3. For a radioactive sample which decays to 12.5% of its initial value in x
days, the half life is given by..
4. Connect two 1o resistors in series, then connect two 1h inductors across
one of the resistors such that the ckt looks like a 1o resistor in series
with a ?-section of a resistor and two inductors. With the series resistance
on the I/p side, calc the transfer function of this ckt
5. Ac signal conditioning is used for inductive and
capacitive/resistive/piezoelectric transducers/all of the above.
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. Given four unit-circle plots identify the one corresponding to a bandpass
filter.
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. 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.
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. Given a two port network in the form of a t find o/p admittance in terms
of y-parameters.
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(j?) 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(pt) with causal and
stable system, causal and unstable system, etc.
29. Given a ckt with a 50 o 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. Inverse laplace transform of 1/s2[d/ds(e-3s/s)]
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 resp.
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 mo/o/ko/..
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 8085
91. 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 0/8/undefined value/..
103. Wien bridge oscillator should initially have closed loop gain
>3/<3 br="">
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 ? 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(?0t) 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....
That's all I can remember! One fact which I wish to mention is that many
questions contained options which were repeated, e.g. Both a) and b) were 5.
It was difficult making a choice in these cases.
Aptitude (70 ques):
Most of the questions were straight forward. There were questions involving
profit and loss, ratio-proportion, di from pie-charts, one rc passage and
other questions from verbal. The ones involving verbal were quite confusing,
as none of the options seemed to fit the question,e.g there were some
questions in which you had to find the word farthest in meaning to a given
word. The word given was judicious, and the options were illegal, obscure,
case and some other. The same was the case with the other four questions of
this sort.
Overall it was an ok sort of paper, though the negligible weightage given to
instrumentation related questions was somewhat surprising.
