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 1. Which of the following is the 6. For open control system which of
definition of proportional band of the following statements is
a controller? incorrect?
a. The range of air output as measured a. Less expensive
variable varies from maximum to b. Recalibration is not required for
minimum maintaining the required quality of
b. The range of measured variables the output
from set value c. Construction is simple and
c. The range of measured variables maintenance easy
through which the air output d. Errors are caused by disturbances
changes from maximum to
minimum 7. In a system zero initial condition
means that
d. Any of the above
a. The system is at rest and no energy
2. Which of the following is the is stored in any of its components
nonlinearity caused by
servomotor? b. The system is working with zero
stored energy
a. Static friction
c. The system is working with zero
b. Backlash reference signals
c. Saturation d. None of the above
d. None of the above 8. Which of the following is the best
3. _________ directly converts method for determining the
temperature into voltage. stability and transient response?
a. Thermocouple a. Root locus
b. Potentiometer b. Bode plot
c. Gear train c. Nyquist plot
d. LVDT d. None of the above
4. Which of the following is 9. Technique gives quick transient
exhibited by Root locus diagrams? and stability response
a. The poles of the transfer function a. Root locus
for a set of parameter values b. Bode
b. The bandwidth of the system c. Nyquist
c. The response of a system to a step d. Nichols
input
10. The first order control system,
d. The frequency response of a system which is well designed, has a
5. Regenerative feedback implies a. Small bandwidth
feedback with
b. Negative time constant
a. Oscillations
c. Large negative transfer function
b. Step input pole
c. Negative sign d. None of the above
d. Positive sign 11. An amplidyne can give which of
the following characteristics?

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 a. Constant current d. None of the above
b. Constant voltage 17. In force-voltage analogy, velocity
c. Constant current as well as constant is analogous to
voltage a. Current
d. Constant current, constant voltage b. Charge
and constant power c. Inductance
12. A.C. servomotor is basically a d. Capacitance
a. Universal motor 18. By which of the following the
b. Single phase induction motor system response can be tested
c. Two phase induction motor better?
a. Ramp input signal
d. Three phase induction motor
b. Sinusoidal input signal
13. In an open loop control system
c. Unit impulse input signal
a. Output is independent of control
input d. Exponentially decaying signal

b. Output is dependent on control 19. The position and velocity errors

input of a type-2 system are

c. Only system parameters have effect a. Constant, constant

on the control output b. Constant, infinity
d. None of the above c. Zero, constant
14. A car is running at a constant d. Zero, zero
speed of 50 km/h, which of the 20. The phase lag produced by
following is the feedback element transportation relays
for the driver?
a. Is independent of frequency
a. Clutch
b. Is inversely proportional to
b. Eyes frequency
c. Needle of the speedometer c. Increases linearly with frequency
d. Steering wheel d. Decreases linearly with frequency
15. A.C. servomotor resembles 21. Which of the following is the
a. Two phase induction motor definition of proportional band of
b. Three phase induction motor a controller?

c. Direct current series motor a. The range of air output as measured

variable varies from maximum to
d. Universal motor minimum
16. Which of the following statements b. The range of measured variables
is correct for a system with gain from set value
margin close to unity or a phase
margin close to zero? c. The range of measured variables
through which the air output
a. The system is relatively stable changes from maximum to
b. The system is highly stable minimum
c. The system is highly oscillatory d. Any of the above

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 22. Which of the following is the a. The system is at rest and no energy
nonlinearity caused by is stored in any of its components
servomotor? b. The system is working with zero
a. Static friction stored energy
b. Backlash c. The system is working with zero
c. Saturation reference signals

d. None of the above d. None of the above

23. _________ directly converts 28. Which of the following is the best
temperature into voltage. method for determining the
stability and transient response?
a. Thermocouple
a. Root locus
b. Potentiometer
b. Bode plot
c. Gear train
c. Nyquist plot
d. LVDT
d. None of the above
24. Which of the following is
exhibited by Root locus 29. Technique gives quick transient
diagrams? and stability response

a. The poles of the transfer function a. Root locus

for a set of parameter values b. Bode
b. The bandwidth of the system c. Nyquist
c. The response of a system to a step d. Nichols
input 30. The first order control system,
d. The frequency response of a system which is well designed, has a
25. Regenerative feedback implies a. Small bandwidth
feedback with b. Negative time constant
a. Oscillations c. Large negative transfer function
b. Step input pole
c. Negative sign d. None of the above
d. Positive sign 31. If the gain of the critical damped
26. For open control system which of system is increased it will behave
the following statements is as
incorrect? a. Oscillatory
a. Less expensive b. Critically damped
b. Recalibration is not required for c. Over-damped
maintaining the required quality of d. Under-damped
the output
32. The capacitance, in force-current
c. Construction is simple and analogy, is analogous to
maintenance easy
a. Momentum
d. Errors are caused by disturbances
b. Velocity
27. In a system zero initial condition
means that c. Displacement

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 d. Mass b. All the coefficients are always
33. The transient response, with nonzero
feedback system, c. Only one of the static error
a. Rises slowly coefficients has a finite nonzero
value
b. Rises quickly
d. None of the above
c. Decays slowly
39. Mass, in force-voltage analogy, is
d. Decays quickly analogous to
34. ________ is an open loop control a. Charge
system.
b. Current
a. Ward Leonard control
c. Inductance
b. Field controlled D.C. motor
d. Resistance
c. Stroboscope
40. An increase in gain, in most
d. Metadyne systems, leads to
35. Is a part of the human a. Smaller damping ratio
temperature control system?
b. Larger damping ratio
a. Digestive system
c. Constant damping ratio
b. Perspiration system
d. None of the above
c. Ear
41. Phase margin of a system is used
d. Leg movement to specify which of the following?
36. The initial response when the a. Frequency response
output is not equal to input is
called b. Absolute stability

a. Transient response c. Relative stability

b. Error response d. Time response

c. Dynamic response 42. The type 0 system has _______ at

the origin.
d. Either of the above
a. No pole
37. A control system in which the
control action is somehow b. Net pole
dependent on the output is known c. Simple pole
as d. Two poles
a. Closed loop system 43. ________ is not a final control
b. Semi-closed loop system element.
c. Open system a. Control valve
d. None of the above b. Potentiometer
38. Which of the following statements c. Electro-pneumatic converter
is correct for any closed loop d. Servomotor
system?
44. Which of the following is an
a. All the coefficients can have zero electromagnetically device?
value
a. Induction relay

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 b. Thermocouple a. Reference and output
c. LVDT b. Reference and input
d. Any of the above c. Input and feedback signal
45. The transfer function technique is d. Output and feedback signal
considered as inadequate under 50. Due to which of the following
which of the following conditions? reasons excessive bond width in
a. Systems having complexities and control systems should be avoided?
nonlinearities a. It leads to slow speed of response
b. Systems having stability problems b. It leads to low relative stability
c. Systems having multiple input c. Noise is proportional to band width
disturbances
d. None of the above
d. All of the above
46. In closed loop control system, 51. In electrical-pneumatic system
with positive value of feedback analogy the current is considered
gain the overall gain of the system analogous to
will
a. Velocity
a. Decrease
b. Pressure
b. Increase
c. Air flow
c. Be unaffected
d. Air flow rate
d. Any of the above
52. Signal will become zero when the
47. An automatic toaster is a feedback signal and reference
________ loop control system. signs are equal.
a. Open a. Input
b. Closed b. Actuating
c. Partially closed c. Feedback
d. Any of the above d. Reference
48. Which of the following should be 53. With feedback _______ increases.
done to make an unstable system a. System stability
stable?
b. Sensitivity
a. The gain of the system should be
decreased c. Gain
b. The gain of the system should be d. Effects of disturbing signals
increased 54. Velocity error constant of a
c. The number of poles to the loop system is measured when the
transfer function should be input to the system is unit
increased ________ function.
d. The number of zeros to the loop a. Parabolic
transfer function should be b. Ramp
increased
c. Impulse
49. The output of a feedback control
d. Step
system must be a function of

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 55. Which of the following can be 61. The frequency and time domain
measured by the use of a are related through which of the
tachogenerator? following?
a. Acceleration a. Laplace Transform and Fourier
b. Speed Integral

c. Speed and acceleration b. Laplace Transform

d. Displacement c. Fourier Integral

56. A differentiator is usually not a d. Either (B) or (C)

part of a control system because it 62. In case of type-1 system steady
a. Reduces damping state acceleration is

b. Reduces the gain margin a. Unity

c. Increases input noise b. Infinity

d. Increases error c. Zero

57. Which of the following is an open d. 10

loop control system? 63. Which of the following statements
a. Field controlled D.C. motor is not necessarily correct for open
control system?
b. Ward Leonard control
a. Input command is the sole factor
c. Metadyne responsible for providing the
d. Stroboscope control action
58. ________ Increases the steady b. Presence of nonlinearities causes
state accuracy. malfunctioning
a. Integrator c. Less expensive
b. Differentiator d. Generally free from problems of
nonlinearities
c. Phase lead compensator
64. Zero initial condition for a system
d. Phase lag compensator
means
59. In a stable control system
a. Input reference signal is zero
backlash can cause which of the
following? b. Zero stored energy
a. Under-damping c. Net initial movement of moving
parts
b. Over-damping
d. System is at rest and no energy is
c. Poor stability at reduced values of
stored in any of its components
open loop gain
65. A controller, essentially, is a
d. Low-level oscillations
a. Sensor
60. The transient response of a
system is mainly due to b. Clipper
a. Inertia forces c. Comparator
b. Internal forces d. Amplifier
c. Stored energy 66. The transfer function is
applicable to which of the
d. Friction
following?

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 a. Linear and time-in variant systems a. Remains unaffected
b. Linear and time-variant systems b. Decreases by the same amount as
c. Linear systems the gain increase

d. Nonlinear systems c. Increases by the same amount as the

gain decrease
67. A conditionally stable system
exhibits poor stability at d. Decreases by the same amount as
the gain decrease
a. Low frequencies
73. In liquid level and electrical
b. Reduced values of open loop gain system analogy, voltage is
c. Increased values of open loop gain considered analogous to
d. None of the above a. Head
68. Which of the following devices is b. Liquid flow
used for conversion of coordinates? c. Liquid flow rate
a. Microsyn d. None of the above
b. Selsyn 74. _______ is the reference input
c. Synchro-resolver minus the primary feedback.
d. Synchro-transformer a. Manipulated variable
69. With feedback ________ reduces. b. Zero sequence
a. System stability c. Actuating signal
b. System gain d. Primary feedback
c. System stability and gain 75. If a step function is applied to the
input of a system and the output
d. None of the above
remains below a certain level for
70. In open loop system all the time, the system is
a. The control action depends on the a. Not necessarily stable
size of the system
b. Stable
b. The control action depends on
c. Unstable
system variables
d. Always unstable
c. The control action depends on the
input signal 76. The effect of error damping is to
d. The control action is independent of a. Provide larger settling lime
the output b. Delay the response
71. A closed loop system is c. Reduce steady state error
distinguished from open loop
system by which of the following? d. Any of the above

a. Servomechanism 77. Which of the following can be

measured by LVDT?
b. Feedback
a. Displacement
c. Output pattern
b. Velocity
d. Input pattern
c. Acceleration
72. The band width, in a feedback
amplifier. d. Any of the above

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 78. Any externally introduced signal 84. The temperature, under thermal
affecting the controlled output is and electrical system analogy, is
called a considered analogous to
a. Feedback a. Voltage
b. Stimulus b. Current
c. Signal c. Capacitance
d. Gain control d. Charge
79. Transfer function of a system is 85. The second derivative input
used to calculate which of the signals modify which of the
following? following?
a. The order of the system a. The time constant of the system
b. The time constant b. Damping of the system
c. The output for any given input c. The gain of the system
d. The steady state gain d. The time constant and suppress the
80. Has tendency to oscillate. oscillations

a. Open loop system 86. ________ is a closed loop system.

b. Closed loop system a. Autopilot for an aircraft

c. Both (A) and (B) b. Direct current generator

d. Neither (A) nor (B) c. Car starter

81. A phase lag lead network d. Electric switch

introduces in the output 87. A good control system has all the
a. Lag at all frequencies following features except

b. Lag at high frequencies and lead at a. Good stability

low frequencies b. Slow response
c. Lag at low frequencies and lead at c. Good accuracy
high frequencies d. Sufficient power handling capacity
d. None of the above 88. Technique is not applicable to
82. The type-1 system has ________ nonlinear system?
at the origin. a. Nyquist Criterion
a. No pole b. Quasi linearization
b. Net pole c. Functional analysis
c. Simple pole d. Phase-plane representation
d. Two poles 89. In a control system integral error
83. Spring constant in force-voltage compensation _________ steady
analogy is analogous to state error
a. Capacitance a. Increases
b. Reciprocal of capacitance b. Minimizes
c. Current c. Does not have any effect on
d. Resistance d. Any of the above

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 90. In thermal-electrical analogy c. Reciprocal of inductance
charge is considered analogous to d. Reciprocal of conductance
a. Heat flow 96. From which of the following
b. Reciprocal of heat flow transfer function can be obtained?
c. Reciprocal of temperature a. Signal flow graph
d. Temperature b. Analogous table
91. Which of the following devices are c. Output-input ratio
commonly used as error detectors d. Standard block system
in instruments?
97. Static error coefficients are used
a. Vernistats as a measure of the effectiveness
b. Microsyns of closed loop systems for
c. Resolvers specified ________ input signal.

d. Any of the above a. Acceleration

92. A control system with excessive b. Velocity

noise, is likely to suffer from c. Position
a. Saturation in amplifying stages d. All of the above
b. Loss of gain 98. In order to increase the damping
c. Vibrations of a badly under-damped system
which of following compensators
d. Oscillations may be used?
93. On which of the following factors a. Phase-lead
does the sensitivity of a closed
loop system to gain changes and b. Phase-lag
load disturbances depend? c. Both (A) and (B)
a. Frequency d. Either (A) and (B)
b. Loop gain 99. ________ can be extended to
c. Forward gain systems which are time-varying?

d. All of the above a. Bode-Nyquist stability methods

94. In an automatic control system b. Transfer functions

which of the following elements is c. Root locus design
not used? d. State model representatives
a. Error detector 100.Which of the following is the
b. Final control element output of a thermocouple?
c. Sensor a. Alternating current
d. Oscillator b. Direct current
95. The viscous friction coefficient, in c. A.C. voltage
force-voltage analogy, is d. D.C. voltage
analogous to
101.When a human being tries to
a. Charge approach an object, his brain acts
b. Resistance as

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 a. an error measuring device. 106.Transfer function is useful for
b. a controller. study of
c. an actuator.
d. an amplifier phase and gain margins.
steady-state behaviour.
102.The most commonly used input steady-state and transient behaviour.
signal(s) in control system is/are transient behaviour

a. step function. 107.The transform function of a

b. ramp or velocity function. system is the Laplace transform
c. accelerating function. of
d. all of the above.
a. impulse response.
103.Which one of the following b. step response.
minimum information is c. frequency response.
necessary to formulate the
problem of control systems 108.What is the characteristic of a
optimization ? good control system?

a. System state equation, output a. Sensitive to parameter variation.

equation and the control vector only. b. Insensitive to input commands.
b. System state equation, output c. Neither sensitive to parameter
equation, control vector and the variation nor sensitive to input
performance index only. commands.
c. System state equation, output d. Insensitive to parameter variation
equation, control vector, constraints but sensitive to input commands
of the problem, the performance
index and system parameters. 109.In a control system, the
d. System state equation, output
equation, control vector and a. state variable can always be
constraints of the problem only. measured.
b. output variable cannot be defined as
104.Actual input applied to the system a function of state variable.
in case of closed loop system is c. output is variable that can be
measured.
a. error signal. d. state variables are dependent on
b. controlling signal. each other.
c. actuating signal.
d. None of the above. 110.In control system, excessive
bandwidth is not employed
105.The largest error between because
reference input and output during
the transient period is called a. noise is proportional to bandwidth.
b. it leads to low relative stability.
a. peak error. c. it leads to slower time response.
b. transient overshoot. d. noise is proportional to the square
c. peak overshoot. of the bandwidth.
d. transient deviation.
111.The transfer function approach is
applicable to

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 a. linear time-invariant as well as 117.If the open-loop transfer function
b. only linear time-invariant systems. is a ratio of a numerator
c. linear as well as non-linear systems. polynomial of degree 'm' and a
d. all systems. denominator polynomial of
degree 'n', then the integer (n-m)
112.An automatic washing machine is represents the number of

a. sampled data controlled system. a. breakaway points.

b. closed loop system. b. unstable poles.
c. open loop system. c. separate root loci.
d. digital control system. d. asymptotes.

113.Time response of an indicating 118.By using feedback in control

instrument is decided by which of systems, the sensitivity to
the following systems? parameter variation is improved.
This is achieved at rate the cost of
a. Mechanical system provided by
pivot and jewel bearing. a. stability.
b. Controlling system. b. loss of system gain.
c. Deflecting system. c. transient response.
d. Damping system. d. reliability

114.With feedback, transient response 119.Consider the following statements

in connection with the feedback of
a. decays quickly. control systems:
b. decays slowly 1. Feedback can improve stability or
c. rises fast. be harmful to stability if it is not
d. no decays. properly applied.
2. Feedback can always improve
115.Dynamic systems are stability.
characterized by change of state 3. In many situations the feedback can
with reduce the effect of noise and
disturbance on system performance.
a. parameter. 4. In general the sensitivity of the
b. input. system gain of a feedback system to a
c. time. parameter variation depends on,
d. None of the above. where the parameter is located.
Which of the above statements are
116.The transfer function of a linear correct?
system is the a. 1, 2 and 3 only.
b. 1, 3 and 4 only.
a. ratio of the output, vO(t), and input, c. 1, 2 and 4 only.
vI(t). d. 1, 2, 3 and 4.
b. ratio of the derivatives of the output 120.Consider the following statements
and the input. in connection with feedback in
c. ratio of the Laplace transform of the control system:
output and that of the input with all 1. With an increase in forward gain,
initial conditions zeros. the output value approaches the input
d. None of these.

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 value in the case of negative feedback c. there is no feedback.
closed-loop system. d. control action is dependent on
2. A negative feedback closed-loop output.
system when subjected to n input of 5
V with forward gain of 1 and a 123.Consider the following statements
feedback gain of 1 gives output 4.999 regarding advantages of close
V. loop negative feedback control
3. The transfer function is dependent systems over open loop systems:
only upon its internal structure and 1. The overall reliability of the closed
components, and is independent of the loop system is more than that of open
input applied to the system. loop system.
4. The overall gain of the block 2. The transient response in a closed
diagram shown is 10. loop system decays more quickly than
in open loop system.
3. In an open loop system, closing of
6
C the loop increases the overall gain of
3 1
R the system.
4. In the closed loop system, the effect
of variation of component parameters
Which of the statements given above on its performance is reduced.
are correct? Which of these statements are correct?

a. Only 1 and 2. a. 1 and 2.

b. Only 3 and 4. b. 1 and 3.
c. Only 2 and 3. c. 1, 2 and 4.
d. Only 1 and 3. d. 3 and 4.

121.Which of the following are the 124.Which one of the following effects
characteristics of closed-loop in the system is NOT caused by
systems? negative feedback?

1. It does not compensate for a. Reduction in gain.

disturbances. b. Increase in bandwidth.
2. It reduces the sensitivity of plant- c. Increase in distortion.
parameter variations. d. Reduction in output impedance.
4. It has the ability to control the
system transient response. 125.With negative feedback, the
3. It does not involve output system stability and system gain
measurements. respectively
Select the correct answer using the
codes given below: a. increases and increases.
b. increases and decreases.
a. 1 and 4. b. 2 and 4. c. decreases and increases.
c. 1 and 3. d. 2 and 3. d. decreases and decreases.

122.In a closed-loop control system 126.Feedback control systems are

changes.
a. control action is independent of
output. a. insensitive to both forward-and
b. output is independent of input. feedback-path parameter

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 b. less sensitive to feedback-path the transfer function Y(s)/U(s) is given
parameter changes than to forward- by
path parameter changes. a. 3(s + 1)
c. less sensitive to forward-path (s2 - 2s + 2)
parameter changes than to b. 3(2s +1)
d. equally sensitive to forward- and (s2 - 2s + 1)
feedback-path parameter feedback- c. (s +1)
path parameter changes. (s2 - 2s + 1)
d. 3(2s + 1)
127.In a speed control system, output (s2 - 2s + 2)
rate feedback is used to changes 131.When deriving the transfer
function of a linear element
a. limit the speed of motor.
b. limit the acceleration of the motor. a. both initial conditions and loading
c. reduce the damping of the system. are taken into account.
d. increase the gain margin. b. initial conditions are taken into
account but the element is assumed
128.In a closed loop system for which to be not loaded.
the output is the speed of a motor, c. initial conditions are assumed to be
the output rate control can be zero but loading is taken into
used to account.
d. initial conditions are assumed to be
a. reduce the damping of the system. zero and the element is assumed to
b. limit the torque output of the motor. be not loaded.
c. limit the speed of the motor.
d. limit the acceleration of the motor. 132.An open loop TF of a unity
feedback system is given by
129.What is the open-loop transfer
function for the system, whose G(s) = 1
characteristic equation is (s +2)2
F(s) = 53 +352 + (K + 2) + 5K = 0? The closed loop transfer function will
have poles at
a. G(s)H(s) = 5K (a) -2, -2
s(s+1)(s +3) (b) -2, -1
b. G(s)H(s) = Ks (c) 2+j,-2-j
s(s + 1)(s +2) (d) -2,2
c. G(s)H(s) = K(s + 5)
s(s+1)(s +2) 133.A transfer function has its zero in
d. G(s)H(s) = 5K the right half of the s-plane. The
s(s + 1)(s +2) function.

130.For the system governed by the a. is positive real.

set of equations b. is minimum phase.
dx1 = 2x1 + x2 + u c. will give stable impulse response.
dt d. is non-minimum phase.

dx2 = -2x1 + u 134.The transfer function of a low-

dt pass RC network is
y = 3x1
a. RCs(1 + RCs)

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 b. 1/(1+RCS) d. denominator polynomial of a
c. RC/(1 + RCs) closed-loop transfer function.
d. S/(1+RCS)
139.The transfer function of the
135.The transfer function of the network shown below is
circuit as shown in the figure is
expressed as

a. R/1+ SRC
b. S/1 + SCR R
c. 1/1 + SCR Vi C VO
d. 1 + SCR

136.The transfer function C/R of the a. 1/S2T2+2ST+1

system shown in the figure is b. 1/S2T2+3ST+1
c. 1/S2T2+ST+1
d. 1/S2T2+1

140.Let a causal LTI system be

characterized by the following
differential equation, with initial
a. G1G2/(1+G1H1+G2H2) rest condition,
b. G1H1G2H2/(1+G1H1)(1+G2H2) d2y + 7dy + 10y(t) = 4x(t) + 5dx(t)
c. G1G2/(1-G1-G2+G1H1G2H2) dt2 dt dt
d. G1G2/(1+G1H1+G2H2+G1H1G2H2) where, x(t) and y(t) are the input and
output respectively. Theimpulse
137.For the block diagram as shown response of the system is (u(t) is the
in figure, the overall transfer unit step function).
function C/R is
a. 2e-2t u(t) - 7e-5tu(t)
b. -2e-2t u(t) + 7e-5tu(t)
c. 7e-2t u(t) - 2e-5tu(t)
d. -7e-2t u(t) + 2e-5tu(t)

141.The transfer function of the

system described by
a. G1G2H1/(1-G1H1-G2H2) d2y + dy = du + 2u
b. G1G2/(1-G1H1+G2H2) dt2 dt dt
c. G1G2H2/(1+G1H1+G2H2) with u as input and y as output is
d. G1G2/(1+G1H1-G2H2)
a. (s+2)/(s+3)
138.The characteristic polynomial of a b. (s+1)/(s2+s)
system can be defined as c. 2/(s2+s)
d. 2s/(s2+s)
a. denominator polynomial of given
transfer function. 142.Select the correct transfer
b. numerator polynomial of given function Vo(s)/Vi(s) from the
transfer function. following,
c. numerator polynomial of a closed-
loop transfer function.

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 145.The input-output relationship of a
linear time invariant continuous
time system is given by
r(t) = d²c(t) + 3dc(t) + 2c(t) ,
dt2 dt
where r(t) and c(t) are input and
output respectively. What is the
transfer function of the system equal
to ?

143.The transfer function for the a. 1/(s2 +s+2)

diagram shown below is given by b. 1/(s2 +3s+2)
which one of the following: c. 2/(s2 +3s+2)
d. 2/(s2 +s+2)

146.Given the relationship between

the input u(t) and the output y(t)
to be
t
y(t) = ∫0 (2+ t - T)e-3(t-T)u(T) dT

the transfer function Y(s)/U(s) is

a. 1/(1 + SRC)
b. SRC/(1 + SRC) a. 2e-2s/s+3
c. SRC/(1 - SRC) b. s+2/(S +3)2
d. 1 + SRC c. 2s +5/s+3
d. 2s+7/(s +3)2
144.As shown in the figure, a negative
feedback system has an 147.The sensitivity of an overall
amplifierof gain 100 with + 10% transfer function M(s) of a closed-
tolerance in the forward path, loop control system with respect
and an attenuator of value 9/100 to the forward path transfer
in the feedback path. The overall function G(s) is
system gain is approximately:
a. G/1+GH
b. G/1-GH
c. 1/1-GH
d. 1/1+GH

Note : Each of the next items consists

of two statements, one labelled as
‘Statement-I’ and the other as
‘Statement II’. Examine these two
statements carefully and select the
answers to these items using the codes
a. 10 + 1% given below:
b. 10 +2% a) Both Statement (I) and Statement (II)
c. 10 +5% are individually true and Statement
d. 10 + 10% (II) is the correct explanation of
Statement (I).

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 b) Both Statement (I) and Statement (II) 153.Statement (I): Lead compensation
are individually true but Statement is used to improve system stability
(II) is not the correct explanation of margins.
Statement (I). Statement (II): Lead compensation
c) Statement (I) is true but Statement achieves the desired result through the
(II) is false. merits of its phase lead contribution.
d) Statement (I) is false but Statement
(II) is true. 154.Statement (I): The polar plot has
148.Statement (I): Open-loop system is limitation for portraying the
inaccurate and unreliable due to frequency response of a system.
internal disturbances and lack of of Statement (II): The calculation of
adequate calibration. frequency response is tedious and does
Statement(II): Closed-loop system is not indicate effect of the individual
inaccurate as it cannotaccount poles and zeros.
environmental or parametric changes
and may become unstable. 155.Statement (I): A large resonance
peak in frequency response also
149.Statement (I): Self-loops can exist corresponds to a large peak
in block diagram but not in signal overshoot in transient response.
flow graph. Statement (II): All the systems which
Statement (II): Both block diagrams exhibit overshoot in time response will
and signal flow graphs are applicable also exhibit resonance.
to linear time-invariant systems.
156.Statement (I): If a ramp input is
150.Statement (I): Transfer function applied to a second-order system,the
approach is inadequate, whentime steady-state error of the response
domain in solution is required. can be reduced by reducingdamping
Statement (II): All initial conditions of and increasing natural frequency of
the system are neglected in derivation of oscillation.
transfer function. Statement (II): In the frequency
response of a second-order system, the
151.Statement (I): Stability of a system change in slope at one of the corner
deteriorates when integral control is frequencies is of +40 dB/decade.
incorporated into it.
Statement (II): With integral control 157.Statement (I): Control system
action, the order of a system increases components for aviation systems are
and higher the order of the system, designed for 400 Hz.
more the system tends to become Statement (II): The weight of the
unstable. components reduces when designed for
higher frequencies.
152.Statement (I): Constant M and N
circles, as also Nichol's charts, are 158.Statement (I): The rotor of a
graphical techniques to assess servomotor is built with
closed-loop performance in resistanceso that its X/R ratio
thefrequency domain. becomes small.
Statement (II): While constant M and Statement (II): The servomotor has
N circles use Nyquist polar plots data, good accelerating characteristics.
Nichol's chart use Bode plots data.

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 159.Statement (I): Servomotors have Statement (II): Nyquist criterion does
small diameter and large axial not give direct value of corner
length. frequencies.
Statement (II): Servomotors must have
low inertia and high starting torque. 167.Statement (I): The network
function N(s) is denoted with scale
160.Statement (I): The state feedback factor multiplied with the ratio of
design is more realistic than zero factors with pole factors.
conventional fixed configuration Statement (II): When there are n zeros
controller design. and m poles, then the poles at infinity
Statement (II): The disadvantage with are of multiplicity or degree of (n – m).
the state feedback is that all the states Similarly when n<m, then the zeros at
must be sensed and fed back for control. infinity are of multiplicity or degree of
(m-n).
161.Statement (I): Elements with non-
minimum phase transfer functions 168.Statement (I): The inductor is not
introduce large phase lags with used to fabricate a lag network as it
increasing frequency resulting in produces time delay and hysteresis
complex compensation problems. loss.
Statement (II): Transportation lag Statement (II): A capacitor cannot be
commonly encountered in process used to fabricate a lag network.
control system is a non-minimum phase
element. 169.Statement (I): Phase lag network is
used to increases stability as well as
162.Statement (I): Centroid is the point bandwidth of the system.
where the root loci break from the Statement (II): Phase lead network
real axis. increases bandwidth of the system.
Statement (II): Centroid is the point of
the real axis where all the asymptotes 170.Statement (I): For type- II or
intersect. higher systems, lead compensator
may be used
163.Statement (I): A root locus is Statement (II): Lead compensator
obtained using the closed-loop poles. increases the margin of stability.
Statement (II): A root locus is plotted
using the open-loop poles. Note : Each of the next items consists
of two statements, one labelled as
164.Statement (I): Inverse root locus is ‘Assertion (A)’ and the other as
the image of the direct root locus. ‘Reason (R)’. Examine these two
Statement (II): Root locus is statements carefully and select the
symmetrical about the imaginary axis. answers to these items using the codes
given below:
165.Statement (I): At breakaway point,
the system is critically damped. a) Both A and R are true and Ris the
Statement (II): At the point where root correct explanation of A.
loci intersect with the imaginary axis, b) Both A and R are true but R is not
the system is marginally stable. the correct explanation of A.
c) A is true but R is false.
166.Statement (I): Roots of closed-loop d) A is false but R is true.
control systems can be obtained
from the Bode plot.

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 171.In the feedback system C(s), R(s) representing the outputs of the various
and D(s) are the system output, blocks of the control system.
input and disturbance, respectively.
(A): For the system 176.(A):Process industry applications
should ideally be tuned for critical
damping.
(R):Critically damped response has no
oseillations in the output.

177.(A): The closed-loop system

C(s) = 5 for a step
R(s) (s+1)(s+5)
input can be approximated by system
C1(s) = 1 for R(s) = 1
R(s) s+1 s
C(s)[R(s) + D(s)] = 1+G(s)
R(s)D(s) 1+G(s)H(s) (R): Both C(s) and C1(s) have
R(S) R(s)
(R):Transfer function of a system is approximately the same transient
defined as the ratio of output Laplace response.
transform and input Laplace transform
setting other inputs and the initial 178.(A):A system may have no steady-
conditions to zero. state error to a step input, but the
same system may exhibit nonzero
172.(A):If the impulse response of a steady state error to ramp input
networkis available, the response to (R):The steady-state error of a system
any arbitrary input can be derived. depends on the 'type' of the open loop
(R):The Laplace transform of unit transfer function.
impulse is unity.
179.(A):Addition of a pole to the
173.(A): For a prototype second order forward path transfer function of
system, the larger the bandwidth, unity feedback system increases the
the faster the system will respond. rise time of step response.
(R): Bandwidth and rise time are (R):The additional pole has the effect of
inversely proportional. increasing the bandwidth of the system.

174.(A):The effects of noise disturbance 180.(A): An addition of real

and parameter variations are zero at s = -z0 in the transfer
relatively easy to visualize and functionG(s)H(s) of a control
access through frequency reponse. system results in the increase of
(R): Frequency response test is suitable stability margin.
for systems with verylarge time (R):An addition of real zero at s =-z0 the
constants. transfer function G(s)H(s) will make the
resultant root loci bend towards left.
175.(A): Signal flow graphs can be used
for block diagram reduction of 181.(A):For a stable feedback control
linear control system. system, the zeros of the
(R):Signal flow graph is a graphical characteristic equation must all be
representation for the variables located in the left-half ofthe s-plane.

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 (R):The poles of the closed-loop transfer 188.(A):Tachogenerator feedback is
function are the zeros ofthe used as minor loop feedback in
characteristic equation. position control systems to improve
stability.
182.(A):If any one of the state variable (R):Tachogenerator provides velocity
is independent of the control u(t), feedback which decreases the damping
the process is said to be completely in the system.
uncontrollable.
(R):There is no way of driving this 189.(A):Adding a pole to the open-loop
particular state variable to a desired state transfer function G(s)H(s) has the
in finite time by means of a control effect of pushing the root loci
effort. towards the R.H. s-plane.
(R):If the number of poles increases the
183.(A):Use of lead compensation angle of asymptotes for the complex
results in increased system roots is reduced.
bandwidth.
(R):The angular contribution of the 190.(A):DC servomotors are more
compensator pole is more than that of commonly used in armature
the compensator zero. controlled mode instead of in field
controlled mode.
184.(A):With lag-lead compensation, (R):Armature controlled dc motors have
the bandwidth of the system isnot higher starting torque than field
affected much. controlled motors.
(R):The effect of lag and lead
compensations at high frequencies 191.(A):All the coefficients of the
cancel one another. characteristic equation should be
positive and no term should be
185.(A):The variation in gain of the missing in the characteristic
system does not alter the phase equation for a system to be stable.
angle plot in the Bode diagram. (R):If some of the coefficients are zero
(R):The phase margin of the system is or negative then the system is not stable.
not affected by the variationin gain of
the system. 192.(A):Servomotors normally have
heavier rotors and lower R/Xratio as
186.(A):The state transition matrix compared to ordinary motors of
represents the free response of the similar ratings.
system. (R):Servomotors should have smaller
(R):The state transition matrix satisfies electrical and mechanical time constants
the homogeneous state equation. for faster response.

187.(A):The number of separate loci of 193.(A):The stability of a closed-loop

the closed loop system system can be obtained from the
corresponding to :- open-loop transfer function
G(jω)H(jω) plot with respect to the
G(s)H(s) = K(s+4) is three. critical point (-1, j0) in G(jω) H(jω)
s(s+1)(s+3) plane.
(R):Number of separate loci is equal to (R):The origin of 1+G(jω)+H(jω)
number of finite poles of G(s)H(s) if the corresponds to (-1, j0) point in G(jω)
latter is more than the number of finite H(jω) plane.
zeros of G(s)H(s).

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 194.(A):Relative stability of a system a. 1
reduces due to the presence of b. 5
transportation lag. c. 10
(R):Transportation lag can be d. 100
conveniently handled by Bode plot.
199.Single step response of a typical
195.(A):For a control system having stepper motor is quite oscillatory,
synchro pair as error detector and dc Brakes are used to reduce or
amplifier as control amplifier, a eliminate oscillations. Which one
phase sensitive detectoris required of the following statements is not
to demodulate in place of ordinary correct regrading use of brakes?
diode detector.
(R):Synchro output is a suppressed a. It provides memory or position
carrier amplitude modulated signal information when motor is switched
which cannot be demodulated by off.
ordinary diode detector. b. It reduces deceleration time.
c. It reduces length of motor load.
196.(A):Stability of a system d. It reduces pullout torque.
deteriorates when integral control is
incorporated in it. 200.If D is the rotor diameter and L,
(R):With integral control order of the the axial length, then a high
system increases, and higher the order of performance ac servomotor is
the system more the system tends to characterized by which one of the
become unstable. following?

197.(A):For a system to be stable, all a. Large D and Large L.

coefficients of the characteristic b. Large D and Small L.
polynomial must be positive. c. Small D and Small L.
(R):All positive coefficients of the d. Small D and Large L.
characteristic polynomial of a system is
a sufficient condition for stability. 201.For a stepper motor, what is the
correct relationship between the
198.The open-loop transfer function maximum slew rate (MSR) and
of a dc motor is given as the load ?
W(s) = 10 When connected in
Va (s) 1 + 10s a. MSR decreases as load is reduced.
feedback as shown below, the b. MSR increases considerably as load
approximate value of ka, that will is increased.
reduce the time constant of the closed c. MSR increases as load is reduced.
loop system by one hundred times as d. MSR remains the same even if the
compared to that of the open-loop load is changed.
system is
202.The desirable features of a
servomotor are

a. low rotor inertia and low bearing

friction.
b. high rotor inertia and high bearing
friction.

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 c. low rotor inertia and high bearing Which of the above statements are not
friction. correct?
d. high rotor inertia and low bearing
friction. a) 1 and 2.
b) 2 and 3.
203.For a tachometer, if θ(t) is the c) 1 and 3.
rotor displacement, e(t) is the d) 1, 2 and 3.
output voltage and K is the
tachometer constant, then the 207.The effect of tachometer feedback
transfer function is defined as in a control system is to reduce

a. Ks² a. only time constant.

b. K/s b. only gain.
c. Ks c. damping.
d. K d. both gain and time constant.

204.The servomotor differs from the 208.In position control systems, the
standard motors principally in device used for providing rate
that, it has feedback is called

a. entirely different construction. a. potentiometer.

b. high inertia and hence high torque. b. synchro.
c. low inertia and torque. c. tachogenerator.
d. low inertia and higher starting d. servomotor.
torque.
209.Which one of the following is
205.A tachometer is added to a required for stability of an ac
servomechanism because servomotor?

a. it is easily adjustable. a. A negative slope on the torque-

b. it can adjust damping. speed curve.
c. it converts velocity of the shaft to a b. A linearized torque-speed curve.
proportional de voltage. c. The ratio of the rotor reactance to
d. it reduces steady-state error. rotor resistance should be high.
d. The rotor diameter should be less
206.Consider the following and axial length large.
statements :
a. Servomotors have lighter rotor as 210.If the rotor axis of a synchro
compared to ordinary motors and transmitter is along the axis of S2,
hence lower inertia. stator winding, when will be the
b. Back emf in field controlled dc electrical zeroing ?
motors acts as minor loop
feedback and results in increased a. Vs1s2 is maximum.
damping and improved transient b. Vs2s3 is maximum.
response. c. Vs2s3 is minimum.
c. Permanent magnetic dc d. Vs3s1 is manimum.
servomotors can be used in either
armature controlled or field- 211.Which one of the following is the
controlled modes. correct statement ? The rotor
resistance to reactance ratio and

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 the moment of inertia of an ac sin 2ωt is ?
servomotor in comparison to an
ordinary 2-Φ induction motor of a. s+2
similar rating are, respectively, (s + 2)2 + 4ω2
b. 2s
a. lower and lower. (s - 2)2 + 4ω2
b. lower and higher. c. 2s
c. higher and higher. (s + 2)2 + 4ω2
d. higher and lower. d. 2s
(s + 2)2 + 2ω2
212.Which of the following can work
as error detecting devices? 216.Considering the root locus
1. A pair of potentiometers. diagram for a system with
2. A pair of synchros. G(s) = K(s + 5) ,
3. A differential transformer. s(s + 2) (s + 4) (s2 + 2s +2)
4. A metadyne. the meetingpoint of the asymptotes on
5. A control transformer. the real axis occurs at ___________.
Select the correct answer using the
codes given below: a. –1.2
Codes: b. –0.85
a. 1, 2 and 5. c. –1.05
b. 2, 3, 4 and 5. d. –0.75
c. 1, 3, 4 and 5.
d. 1, 2, 3 and 4. 217.Figure shows a circuit for which
switch S is kept open for a long
213.In case of an armature controlled time and then closed at t = 0. The
separately excited dc motor drive dynamic equation governing the
with closed-loop speed control, an circuit will then be ________.
inner current loop is useful
because it

a. limits the speed of the motor to a

safe value.
b. helps in improving the drive energy
efficiency.
c. limits the peak current of the motor
to the permissible value.
d. reduces the steady state speed error. a. 9i  4∫i dt  180
i(0)  10
214.The steady-state error of a b. 12i  4 di = 180
feedback control system with an dt
acceleration input becomes finite i(0)  25
in a c. 9i + 4 di = 180
dt
a. type 0 system. i(0) = 15
b. type 1 system. d. 12i  4 ∫i dt  180
c. type 2 system. i(0)  15
d. type 3 system.

215.The Laplace transform of e−2t

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 218.Considering the unity feedback
system of Fig. the settling time of
the resulting second order system
for 2% tolerance band will be

a. 3.33
b. 4.5
c. 2.25
d. 2.84

219.If for a control system, the

Laplace transform of error e(t) is
given as 8(s  3) then the steady
state s (s  10) value of the
error works out as____.

a. 3.6
b. 1.8
c. 3.2
d. 2.4

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 DRONACHARYA ACADEMY
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