Control System MCQs with Answers

There is a wide range of questions and reasons for asking Control System MCQs. The way one learns varies from individual to individual and it mainly depends on the motive and goal of the person. Some start off their engineering course by taking these control system exams as they find them helpful in getting to know how the basics work. These MCQs have solutions, explanations for interviews, competitive examinations, and entrance tests.

Control System MCQs with Answers

1. In an open loop control system

(a) Output is independent of control input

(b) Output is dependent on control input

(c) Only system parameters have effect on the control output

(d) None of the above

Answer: Output is independent of control input

2. For open control system which of the following statements is incorrect?

(a) Less expensive

(b) Recalibration is not required for maintaining the required quality of the output

(c) Construction is simple and maintenance easy

(d) Errors are caused by disturbances

Answer: Recalibration is not required for maintaining the required quality of the output

3. A control system in which the control action is somehow dependent on the output is known as

(a) Closed loop system

(b) Semiclosed loop system

(c) Open system

(d) None of the above

Answer: Closed loop system

4. In closed loop control system, with positive value of feedback gain the overall gain of the system will

(a) decrease

(b) increase

(c) be unaffected

(d) any of the above

Answer: decrease

5. Which of the following is an open loop control system?

(a) Field controlled D.C. motor

(b) Ward leonard control

(c) Metadyne

(d) Stroboscope

Answer: Field controlled D.C. motor

6. Which of the following statements is not necessarily correct for open control system ?

(a) Input command is the sole factor responsible for providing the control action

(b) Presence of non-linearities causes malfunctioning

(c) Less expensive

(d) Generally free from problems of non-linearities

Answer: Presence of non-linearities causes malfunctioning

7. In open loop system

(a) the control action depends on the size of the system

(b) the control action depends on system variables

(c) the control action depends on the input signal

(d) the control action is independent of the output

Answer: the control action is independent of the output

8. Has tendency to oscillate.

(a) Open loop system

(b) Closed loop system

(c) Both(a) and (b)

(d) Neither(a) nor (b)

Answer: Closed loop system

9. A good control system has all the following features except

(a) good stability

(b) slow response

(c) good accuracy

(d) sufficient power handling capacity

Answer: slow response

10. A car is raining at a constant speed of 50 km/h, which of the following is the feedback element for the driver?

(a) Clutch

(b) Eyes

(c) Needle of the speedometer

(d) Steering wheel

Answer: Needle of the speedometer

11. The initial response when the output is not equal to input is called

(a) Transient response

(b) Error response

(c) Dynamic respons

(d) Either of the above

Answer: Transient response

12. A control system working under unknown random actions is called

(a) computer control system

(b) digital data system

(c) stochastic control system

(d) adaptive control system

Answer: stochastic control system

13. An automatic toaster is a ______ loop control system.

(a) open

(b) closed

(c) partially closed

(d) any of the above

Answer: open

14. Any externally introduced signal affecting the controlled output is called a

(a) feedback

(b) stimulus

(c) signal

(d) gain control

Answer: stimulus

15. A closed loop system is distinguished from open loop system by which of the following?

(a) Servomechanism

(b) Feedback

(c) Output pattern

(d) Input pattern

Answer: Feedback

16 Is a part of the human temperature control system.

(a) Digestive system

(b) Perspiration system

(c) Ear

(d) Leg movement

Answer: Perspiration system

17. By which of the following the control action is determined when a man walks along a path?

(a) Brain

(b) Hands

(c) Legs

(d) Eyes

Answer: Eyes

18. Is a closed loop system.

(a) Auto-pilot for an aircraft

(b) Direct current generator

(c) Car starter

(d) Electric switch

Answer: Auto-pilot for an aircraft

19. Which of the following devices are commonly used as error detectors in instruments?

(a) Vernistats

(b) Microsyns

(c) Resolvers

(d) Any of the above

Answer: Any of the above

20. Which of the following should be done to make an unstable system stable?

(a) The gain of the system should be decreased

(b) The gain of the system should be increased

(c) The number of poles to the loop transfer function should be increased

(d) The number of zeros to the loop transfer function should be increased

Answer: The gain of the system should be increased

21. Increases the steady state accuracy.

(a) Integrator

(b) Differentiator

(c) Phase lead compensator

(d) Phase lag compensator

Answer: Integrator

22. A.C. servomotor resembles

(a) two phase induction motor

(b) Three phase induction motor

(c) direct current series motor

(d) universal motor

Answer: two phase induction motor

23. As a result of introduction of negative feedback which of the following will not decrease?

(a) Band width

(b) Overall gain

(c) Distortion

(d) Instability

Answer: Band width

24. Regenerative feedback implies feedback with

(a) oscillations

(b) step input

(c) negative sign

(d) positive sign

Answer: positive sign

25. The output of a feedback control system must be a function of

(a) reference and output

(b) reference and input

(c) input and feedback signal

(d) output and feedback signal

Answer: reference and output

26. Is an open loop control system.

(a) Ward Leonard control

(b) Field controlled D.C. motor

(c) Stroboscope

(d) Metadyne

Answer: Field controlled D.C. motor

27. A control system with excessive noise, is likely to suffer from

(a) saturation in amplifying stages

(b) loss of gain

(c) vibrations

(d) oscillations

Answer: saturation in amplifying stages

28. Zero initial condition for a system means

(a) input reference signal is zero

(b) zero stored energy

(c) ne initial movement of moving parts

(d) system is at rest and no energy is stored in any of its components

Answer: system is at rest and no energy is stored in any of its components

29. Transfer function of a system is used to calculate which of the following?

(a) The order of the system

(b) The time constant

(c) The output for any given input

(d) The steady state gain

Answer: The output for any given input

30. The band width, in a feedback amplifier.

(a) remains unaffected

(b) decreases by the same amount as the gain increase

(c) increases by the sane saaaajajt as the gain decrease

(d) decreases by the same amount as the gain decrease

Answer: increases by the sane saaaajajt as the gain decrease

31. On which of the following factors does the sensitivity of a closed loop system to gain changes and load disturbances depend?

(a) Frequency

(b) Loop gain

(c) Forward gain

(d) All of the above

Answer: All of the above

32. The transient response, with feedback system

(a) rises slowly

(b) rises quickly

(c) decays slowly

(d) decays quickly

Answer: decays quickly

33. The second derivative input signals modify which of the following?

(a) The time constant of the system

(b) Damping of the system

(c) The gain of the system

(d) The time constant and suppress the oscillations

(e) None of the above

Answer: None of the above

34. Which of the following statements is correct for any closed loop system?

(a) All the co-efficients can have zero value

(b) All the co-efficients are always non-zero

(c) Only one of the static error co-efficients has a finite non-zero value

(d) None of the above

Answer: Only one of the static error co-efficients has a finite non-zero value

35. Which of the following statements is correct for a system with gain margin close to unity or a phase margin close to zero?

(a) The system is relatively stable

(b) The system is highly stable

(c) The system is highly oscillatory

(d) None of the above

Answer: The system is highly oscillatory

36. Due to which of the following reasons excessive bond width in control systems should be avoided?

(a) It leads to slow speed of response

(b) It leads to low relative stability

(c) Noise is proportional to band width

(d) None of the above

Answer: Noise is proportional to band width

37. In a stable control system backlash can cause which of the following?

(a) Underdamping

(b) Overdamping

(c) Poor stability at reduced values of open loop gain

(d) Low-level oscillations

Answer: Low-level oscillations

38. In an automatic control system which of the following elements is not used?

(a) Error detector

(b) Final control element

(c) Sensor

(d) Oscillator

Answer: Oscillator

39. In a control system the output of the controller is given to

(a) final control element

(b) amplifier

(c) comparator

(d) sensor

Answer: final control element

40. A controller, essentially, is a

(a) sensor

(b) clipper

(c) comparator

(d) amplifier

Answer: comparator

41. Which of the following is the input to a controller?

(a) Servo signal

(b) Desired variable value

(c) Error signal

(d) Sensed signal

Answer: Error signal

42. The on-off controller is a _____ system.

(a) digital

(b) linear

(c) non-linear

(d) discontinuous

Answer: non-linear

43. The capacitance, in force-current analogy, is analogous to

(a) momentum

(b) velocity

(c) displacement

(d) mass

Answer: mass

44. The temperature, under thermal and electrical system analogy, is considered analogous to

(a) voltage

(b) current

(c) capacitance

(d) charge

Answer: voltage

45. In electrical-pneumatic system analogy the current is considered analogous to

(a) velocity

(b) pressure

(c) air flow

(d) air flow rate

Answer: air flow rate

46. In liquid level and electrical system analogy, voltage is considered analogous to

(a) head

(b) liquid flow

(c) liquid flow rate

(d) none of the above

Answer: head

47. The viscous friction co-efficient, in force-voltage analogy, is analogous to

(a) charge

(b) resistance

(c) reciprocal of inductance

(d) reciprocal of conductance

Answer: resistance

48. In force-voltage analogy, velocity is analogous to

(a) current

(b) charge

(c) inductance

(d) capacitance

Answer: current

49. In thermal-electrical analogy charge is considered analogous to

(a) heat flow

(b) reciprocal of heat flow

(c) reciprocal of temperature

(d) temperature

Answer: temperature

50. Mass, in force-voltage analogy, is analogous to

(a) charge

(b) current

(c) inductance

(d) resistance

Answer: inductance

51. The transient response of a system is mainly due to

(a) inertia forces

(b) internal forces

(c) stored energy

(d) friction

Answer: stored energy

52. Signal will become zero when the feedback signal and reference signs are equal.

(a) Input

(b) Actuating

(c) Feedback

(d) Reference

Answer: Actuating

53. A signal other than the reference input that tends to affect the value of controlled variable is known as

(a) disturbance

(b) command

(c) control element

(d) reference input

Answer: disturbance

54. The transfer function is applicable to which of the following?

(a) Linear and time-in variant systems

(b) Linear and time-variant systems

(c) Linear systems

(d) Non-linear systems

Answer: Linear and time-in variant systems

55. From which of the following transfer function can be obtained?

(a) Signal flow graph

(b) Analogous table

(c) Output-input ratio

(d) Standard block system

Answer: Signal flow graph

56. Is the reference input minus the primary feedback.

(a) Manipulated variable

(b) Zero sequence

(c) Actuating signal

(d) Primary feedback

Answer: Actuating signal

57. The term backlash is associated with

(a) servomotors

(b) induction relays

(c) gear trains

(d) any of the above

Answer: gear trains

58. With feedback _____ increases.

(a) system stability

(b) sensitivity

(c) gain

(d) effects of disturbing signals

Answer: system stability

59. By which of the following the system response can be tested better?

(a) Ramp input signal

(b) Sinusoidal input signal

(c) Unit impulse input signal

(d) Exponentially decaying signal

Answer: Unit impulse input signal

60. In a system zero initial condition means that

(a) The system is at rest and no energy is stored in any of its components

(b) The system is working with zero stored energy

(c) The system is working with zero reference signal

(d) None of these

Answer: The system is at rest and no energy is stored in any of its components

61. In a system low friction co-efficient facilitates

(a) reduced velocity lag error

(b) increased velocity lag error

(c) increased speed of response

(d) reduced time constant of the system

Answer: reduced velocity lag error

62. Hydraulic torque transmission system is analog of

(a) amplidyneset

(b) resistance-capacitance parallel circuit

(c) motor-generator set

(d) any of the above

Answer: motor-generator set

63. Spring constant in force-voltage analogy is analogous to

(a) capacitance

(b) reciprocal of capacitance

(c) current

(d) resistance

Answer: reciprocal of capacitance

64. The frequency and time domain are related through which of the following?

(a) Laplace Transform and Fourier Integral

(b) Laplace Transform

(c) Fourier Integral

(d) Either (b) or (c)

Answer: Laplace Transform and Fourier Integral

65. An increase in gain, in most systems, leads to

(a) smaller damping ratio

(b) larger damping ratio

(c) constant damping ratio

(d) none of the above

Answer: smaller damping ratio

66. Static error coefficients are used as a measure of the effectiveness of closed loop systems for
specified ________ input signal.

(a) acceleration

(b) velocity

(c) position

(d) all of the above

Answer: all of the above

67. A conditionally stable system exhibits poor stability at

(a) low frequencies

(b) reduced values of open loop gain

(c) increased values of open loop gain

(d) none of the above

Answer: reduced values of open loop gain

68. The type 0 system has ______ at the origin.

(a) no pole

(b) net pole

(c) simple pole

(d) two poles

Answer: no pole

69. The type 1 system has ______ at the origin.

(a) no pole

(b) net pole

(c) simple pole

(d) two poles

Answer: simple pole

70. The type 2 system has ______ at the origin.

(a) no net pole

(b) net pole

(c) simple pole

(d) two poles

Answer: two poles

71. The position and velocity errors of a type-2 system are

(a) constant, constant

(b) constant, infinity

(c) zero, constant

(d) zero, zero

Answer: zero, constant

72. Velocity error constant of a system is measured when the input to the system is unit _______ function.

(a) parabolic

(b) ramp

(c) impulse

(d) step

Answer: ramp

73. In case of type-1 system steady state acceleration is

(a) unity

(b) infinity

(c) zero

(d) 10

Answer: infinity

74. If a step function is applied to the input of a system and the output remains below a certain level for all the time, the system is

(a) not necessarily stable

(b) stable

(c) unstable

(d) always unstable

Answer: not necessarily stable

75. Which of the following is the best method for determining the stability and transient response?

(a) Root locus

(b) Bode plot

(c) Nyquist plot

(d) None of the above

Answer: Root locus

76. Phase margin of a system is used to specify which of the following?

(a) Frequency response

(b) Absolute stability

(c) Relative stability

(d) Time response

Answer: Relative stability

77. Addition of zeros in transfer function causes which of the following?

(a) Lead-compensation

(b) Lag-compensation

(c) Lead-lag compensation

(d) None of the above

Answer: Lag-compensation

78. Technique is not applicable to nonlinear system?

(a) Nyquist Criterion

(b) Quasi linearization

(c) Functional analysis

(d) Phase-plane representation

Answer: Nyquist Criterion

79. In order to increase the damping of a badly underdamped system which of following compensators may be used?

(a) Phase-lead

(b) Phase-lag

(c) Both(a) and (b)

(d) Either(a) and (b)

Answer: Phase-lead

80. The phase lag produced by transportation relays

(a) is independent of frequency

(b) is inversely proportional to frequency

(c) increases linearly with frequency

(d) decreases linearly with frequency

Answer: increases linearly with frequency

81. In a stable control system saturation can cause which of the following?

(a) Low-level oscillations

(b) High-level oscillations

(c) Conditional stability

(d) Overdamping

Answer: Conditional stability

82. Which of the following can be measured by the use of a tachogenerator?

(a) Acceleration

(b) Speed

(c) Speed and acceleration

(d) Displacement

Answer: Speed

83. Is not a final control element

(a) Control valve

(b) Potentiometer

(c) Electropneumatic converter

(d) Servomotor

Answer: Potentiometer

84. Which of the following is the definition of proportional band of a controller?

(a) The range of air output as measured variable varies from maximum to minimum

(b) The range of measured variables from set value

(c) The range of measured variables through which the air output changes from maximum to minimum

(d) Any of the above

Answer: The range of measured variables through which the air output changes from maximum to minimum

85. In pneumatic control systems the control valve used as final control element converts

(a) pressure signal to electric signal

(b) pressure signal to position change

(c) electric signal to pressure signal

(d) position change to pressure signal

Answer: pressure signal to position change

86. Pressure error can be measured by which of the following?

(a) Differential bellows and straingauge

(b) Selsyn

(c) Strain gauge

(d) Strain gauge and potentiometer

Answer: Differential bellows and straingauge

87. Which of the following devices is used for conversion of co-ordinates?

(a) Microsyn

(b) Selsyn

(c) Synchro-resolver

(d) Synchro-transformer

Answer: Synchro-resolver

88. The effect of error damping is to

(a) provide larger settling lime

(b) delay the response

(c) reduce steady state error

(d) any of the above

Answer: reduce steady state error

89. Technique gives quick transient and stability response

(a) Root locus

(b) Bode

(c) Nyquist

(d) Nichols

Answer: Root locus

90. A phase lag lead network introduces in the output

(a) lag at all frequencies

(b) lag at high frequencies and lead at low frequencies

(c) lag at low frequencies and lead at high frequencies

(d) none of the above

Answer: lag at low frequencies and lead at high frequencies

91. Which of the following is the non-linearity caused by servomotor?

(a) Static friction

(b) Backlash

(c) Saturation

(d) None of the above

Answer: Saturation

92. Can be extended to systems which are time-varying?

(a) Bode-Nyquist stability methods

(b) Transfer functions

(c) Root locus design

(d) State model representatives

Answer: State model representatives

93. When the initial conditions of a system are specified to be zero it implies that the system is

(a) at rest without any energy stored in it

(b) working normally with reference input

(c) working normally with zero reference input

(d) at rest but stores energy

Answer: at rest but stores energy

94. Which of the following is an electromagnetically device?

(a) Induction relay

(b) Thermocouple

(c) LVDT

(d) Any of the above

Answer: LVDT

95. A differentiator is usually not a part of a control system because it

(a) reduces damping

(b) reduces the gain margin

(c) increases input noise

(d) increases error

Answer: increases input noise

96. If the gain of the critical damped system is increased it will behave as

(a) oscillatory

(b) critically damped

(c) overdamped

(d) underdamped

Answer: underdamped

97. In a control system integral error compensation _______ steady state error

(a) increases

(b) minimizes

(c) does not have any effect on

(d) any of the above

Answer: minimizes

98. With feed back _____ reduces.

(a) system stability

(b) system gain

(c) system stability and gain

(d) none of the above

Answer: system gain

99. An amplidyne can give which of the following characteristics?

(a) Constant current

(b) Constant voltage

(c) Constant current as well as constant voltage

(d) Constant current, constant voltage and constant power

Answer: Constant current, constant voltage and constant power

100. Which of the following can be measured by LVDT?

(a) Displacement

(b) Velocity

(c) Acceleration

(d) Any of the above

Answer: Any of the above

101. Directly converts temperature into voltage.

(a) Thermocouple

(b) Potentiometer

(c) Gear train

(d) LVDT

Answer: Thermocouple

102. The transfer function technique is considered as inadequate under which of the following conditions?

(a) Systems having complexities and non-linearities

(b) Systems having stability problems

(c) Systems having multiple input disturbances

(d) All of the above

Answer: All of the above

103. Which of the following is the output of a thermocouple?

(a) Alternating current

(b) Direct current

(c) A.C. voltage

(d) D.C. voltage

Answer: D.C. voltage

104. A.C. servomotor is basically a

(a) universal motor

(b) single phase induction motor

(c) two phase induction motor

(d) three phase induction motor

Answer: two phase induction motor

105. The first order control system, which is well designed, has a

(a) small bandwidth

(b) negative time constant

(c) large negative transfer function pole

(d) none of the above

Answer: large negative transfer function pole

106. Which of the following is exhibited by Root-locus-diagrams?

(a) The poles of the transfer function for a set of parameter values

(b) The bandwidth of the system

(c) The response of a system to a step input

(d) The frequency response of a system

Answer: The poles of the transfer function for a set of parameter values

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