ECE - Automatic Control Systems Quiz (or) MCQ

1 .

A) Control system is a feedback system that can be both positive and negative

B) Control system is a system in which the output is controlled by varying the input

C) Control System is a system in which the input is controlled by varying the output

D) Control system is a device that will not manage or regulate the behaviour of other devices using control loops

Correct Answer : Control system is a system in which the output is controlled by varying the input

Explanation : Control System is a system in which the output is controlled by varying the input. A Control system is a device that will manage, command, direct or regulate the behaviour of other devices using control loops.

2 .

Which of the following is not the feature of a modern control system?

A) No oscillation

B) Accuracy

C) Quick response

D) Correct power level

Correct Answer : No oscillation

Explanation : For a good control system the speed of response and stability must be high and for the slow and sluggish response is not used and undesirable.

3 .

In root locus analysis the breakaway and break in points

A) lie on the real axis

B) Always occur in complex conjugate pairs

C) Either lie on the real axis or occur in complex conjugate pairs

D) None of the above

Correct Answer : Either lie on the real axis or occur in complex conjugate pairs

4 .

The complicated shapes in the polar plots are only due to time constants in the numerator of transfer functions.

A) True

A)

B) False

B)

C) Can Not Say

C)

D) None of the above

D)

Correct Answer : True

5 .

What is the characteristic of a good control system?

A) Sensitive to parameter variation

B) Insensitive to the input command

C) Neither sensitive to parameter variations nor sensitive to input commands

D) Insensitive to the parameter variation but sensitive to the input commands

Correct Answer : Insensitive to the parameter variation but sensitive to the input commands

Explanation : In a good control system, the output is sensitive to input variations but insensitive to parameter variations.

6 .

Which of the following element is not used in an automatic control system?

A) Sensor

B) Oscillator

C) Error detector

D) Final control element

Correct Answer : Oscillator

Explanation : In an automatic control system oscillator is not used because the oscillator increases the oscillations but our aim is to reduce the oscillations and hence oscillator is not used.

7 .

A control system working under unknown random actions is called __________

A) Digital data system

B) Adaptive control system

C) Stochastic control system

D) Computer control system

Correct Answer : Stochastic control system

Explanation : A control system is a system which is having feedback and can be both positive and negative and working under unknown random actions is called stochastic control system.

8 .

Which of the following features is not associated with Nichols chart?

A) It is symmetric about -180°

B) M loci are centred about (0 dB, -180°) point

C) (0 dB, -180°) point on Nichols chart represent critical Point (-1, 0)

D) The frequency at intersection of G (jω) locus and M = +3 dB locus gives bandwidth of closed loop system

Correct Answer : The frequency at intersection of G (jω) locus and M = +3 dB locus gives bandwidth of closed loop system

9 .

Mechanical impedance is the ratio of

A) rms force to rms velocity

B) rms force to rms displacement

C) rms velocity to rms displacement

D) None of the above

Correct Answer : rms force to rms velocity

Explanation : In force voltage analogy force is analogous to voltage and velocity to current. Just as v/i = z , force/velocity = mechanical impedance.

10 .

Whether a linear system is stable or unstable that it

A) is a property of the system only

B) depends on the input function only

C) Both (A) and (B)

D) Either (A) or (B)

Correct Answer : is a property of the system only

11 .

If a system is to follow arbitrary inputs accurately the bandwidth should be

A) large

B) small

C) very small

D) Neither (A) nor (B)

Correct Answer : large

12 .

Assertion (A) : Potentiometers can not be used as error detectors in position control systems.

Reason (R) : The resolution of a potentiometer places an upper limit on its accuracy

A) A is correct but R is wrong

A)

B) R is correct but A is wrong

B)

C) Both A and R are correct and R is correct explanation of A

C)

D) Both A and R are correct but R is not correct explanation of A

D)

Correct Answer : R is correct but A is wrong

13 .

A stepper motor is_________.

A) a two phase induction motor

B) is a kind of rotating amplifier

C) is an electromagnetic transducer used to convert an angular position of shaft into electrical signal

D) is an electromechanical device which actuates a train of step angular movements in response to a train of input pulses on one to one basis

Correct Answer : is an electromechanical device which actuates a train of step angular movements in response to a train of input pulses on one to one basis

14 .

From the noise point of view, bandwidth should

A) be large

B) not be too large

C) should be infinite

D) should be as large as possible

Correct Answer : not be too large

Explanation : If noise is to be eliminated, bandwidth cannot be large.

15 .

When a unit step voltage drives a lag network the output

A) remains constant at unit step value

B) decreases exponentially from 1 to 0

C) increases exponentially from zero to final value

D) None of the above

Correct Answer : increases exponentially from zero to final value

Explanation :

At t = 0 the capacitor behaves as a short-circuit and output voltage is 0. At t = ∞ capacitor behaves as an open-circuit and V₀ = V_i.

16 .

A system has its two poles on the negative real axis and one pair of poles lies on jω axis. The system is

A) stable

B) unstable

C) limitedly stable

D) Either (A) or (B)

Correct Answer : limitedly stable

17 .

Bellows converts

A) pressure difference into displacement

B) pressure difference into voltage

C) displacement into pressure difference

D) None of the above

Correct Answer : pressure difference into displacement

Explanation : To measure pressure, it is convenient to convert pressure into displacement and then use a displacement transducer.

18 .

For the transport lag G(jω) = e^-jωT, the magnitude is always equal to

A)

B) 0.5

B)

C) 1

C)

D) 10

D)

Correct Answer : 1

Explaination : Magnitude is 1.

19 .

The log magnitude curve for a constant gain K is a

A) horizontal straight line

B) an inclined line having slope K

C) an inclined line having slope -K

D) horizontal straight line of magnitude 20 log K decibels

Correct Answer : horizontal straight line of magnitude 20 log K decibels

Explanation :

The factor K in the numerator of G(jω) gives is straight line at 20 log₁₀ K in Bode plot.

20 .

A lag compensator

A) Speeds up the transient response of the system

B) Improves steady state behavior and preserves the transient response of the system

C) Improves steady state behavior of the system

D) Improves steady state behavior and speeds up the transient response of the system

Correct Answer : Improves steady state behavior and preserves the transient response of the system

21 .

A lead compensator

A) Speeds up the transient response

B) Increases the stability margin

C) Increases the stability margin and speeds up the transient-response.

D) None of the above

Correct Answer : Increases the stability margin and speeds up the transient-response.

22 .

The relative stability of a system is given by

A) Gain margin alone

B) Phase margin alone

C) Both phase and gain margins

D) Either (A) or (B)

Correct Answer : Both phase and gain margins

23 .

Which of the following is an open loop control system?

A) Metadyne

B) Stroboscope

C) Ward Leonard control

D) Field controlled D.C. motor

Correct Answer : Field controlled D.C. motor

Explanation : Open loop control systems are the systems that have no feedback and cannot be used to obtain the desired response and field controlled system is an open loop control system.

24 .

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

A) Only one of the static error co-efficient has a finite non-zero value

B) All the co-efficient can have zero value

C) All the co-efficient are always non-zero

D) All of the above

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

Explanation : Closed loop systems are the systems with positive and negative feedback and for standard test signals error constants are defined and for one of the inputs one of the static error co-efficient has a finite non-zero value.

25 .

What should be the nature of bandwidth for a good control system?

A) Small

B) Medium

C) Large

D) All of the above

Correct Answer : Large

Explanation : Bandwidth is defined as the difference in the highest frequency and lowest frequency and bandwidth must be large for the good control system and for higher bandwidth noise is also large.

26 .

The output of the feedback control system must be a function of ____________

A) Reference input

B) Input and feedback signal

C) Reference output

D) Output and feedback signal

Correct Answer : Input and feedback signal

Explanation : Feedback control system has the property of reducing the error and that is by differencing the output with the desired output and as the equation of the output of the system is C=GR/1+GH.

27 .

Which of the following statement is true about Feedback control system?

A) Equally sensitive to forward feedback path parameter changes

B) Insensitive to both forward and feedback path parameter changes

C) Less sensitive to feedback path parameter changes than to forward path parameter changes

D) Less sensitive to forward path parameter changes than to feedback path parameter changes

Correct Answer : Less sensitive to forward path parameter changes than to feedback path parameter changes

Explanation : Feedback control system can be positive and negative but positive feedback systems less widely used as the positive feedback systems are more sensitive to parameter variations but negative feedback are less sensitive to change in G than a change in H.

28 .

A lag compensator is essentially a

A) low pass filter

B) high pass filter

C) band pass filter

D) Either (A) or (B)

Correct Answer : low pass filter

Explanation :

29 .

Stepper motors find applications in

A) printers

B) X-Y plotters

C) numerically controlled machining equipment

D) All of the above

Correct Answer : All of the above

Explanation : Stepper motors are used in all these applications.

30 .

For type 2 system, the magnitude and phase angle of the term (jω)² in the denominator, at ω = 0, are respectively

A) 0 and - 90°

A)

B) 0 and + 90°

B)

C) infinity and - 180°

C)

D) infinity and + 180°

D)

Correct Answer : infinity and - 180°

Explaination :

31 .

In an integral controller

A) the rate of change of output is proportional to input

B) the output is proportional to input

C) the output is proportional to rate of change of input

D) None of the above

Correct Answer : the rate of change of output is proportional to input

Explanation : Output is proportional to integral of input or rate of change of output is proportional to input.

32 .

In the given figure x₆ =

A) de(ax₁ + bx₂ + cx₃)

A)

B) (a + b + c) (x₁ + x₂ + x₃) (d + e)

B)

C) (ax₁ + bx₂ + cx₃) (d + e)

C)

D) a b c d e (x₁ + x₂ + x₃)

D)

Correct Answer : de(ax₁ + bx₂ + cx₃)

Explaination :

The input x₁ is multiplied by a, x₂, by b and x₃ by c. The sum total is multiplied by d and e.

33 .

Transport lag usually exists in

A) Thermal systems

B) Thermal, hydraulic and pneumatic systems

C) Pneumatic systems

D) Hydraulic systems and thermal systems

Correct Answer : Thermal, hydraulic and pneumatic systems

34 .

Robotic manipulator arms mostly use

A) Hydraulic actuator

B) Pneumatic actuator

C) Electric motor actuator

D) None of the above

Correct Answer : Electric motor actuator

35 .

Nichol's chart is symmetric about -180° axis.

A) True

B) False

C) Can Not Say

D) None of the above

Correct Answer : True

36 .

Bode magnitude plot is drawn between

A) dB magnitude and ω

B) dB magnitude and log ω

C) magnitude of network function and ω

D) None of the above

Correct Answer : dB magnitude and log ω

37 .

In a minimum phase system

A) all poles lie in the left half plane

B) all poles lie in the right half plane

C) all zeros lie in the left half plane

D) all except one pole or zero lie in the left half plane

Correct Answer : all zeros lie in the left half plane

Explanation : For stability poles must be in left half plane. Zeros in left half plane lead to minimum phase shift.

38 .

The entries in the first column of Routh array of a fourth order are 5, 2, - 0.1, 2, 1. The number of poles in the right half plane are

A) 1

B) 2

C) 3

D) 4

Correct Answer : 2

Explanation : Two sign changes and hence two poles in right half plane.

39 .

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

A) Overdamping

B) Underdamping

C) Low-level oscillations

D) Poor stability at reduced values of open loop gain

Correct Answer : Low-level oscillations

Explanation : In stable control systems, backlash is the form of the error which may cause low level of oscillations and hence can be useful sometimes as it increases the damping.

40 .

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

A) Sensor

B) Amplifier

C) Comparator

D) Final control element

Correct Answer : Final control element

Explanation : In control system the output of the controller is given to the final control element it may be the plant or any other controller which-ever is used in the control circuit.

41 .

A Control System with excessive noise, is likely to suffer from which of the following?

A) Vibrations

B) Loss of gain

C) Oscillations

D) Saturation in amplifying stages

Correct Answer : Saturation in amplifying stages

Explanation : Noise is defined as the unwnated output due to the input and this is due to the excessive bandwidth and control system with excessive noise is likely to suufer from saturation in amplifying stages.

42 .

In a temperature control system, what conversion in signal takes place?

A) Analog to Digital

B) Digital to Analog

C) Error to Analog

D) Error to Digital

Correct Answer : Analog to Digital

Explanation : In a temperature control system, analog to digital conversion of signals take place. Automatic systems don’t understand analog signals as they only take digital inputs in the form of 0 & 1 so we use a analog to digital converter which converts the signal.

43 .

Which of the following control systems have unpredictable & non-repeatable?

A) Static control systems

B) Stochastic control systems

C) Dynamic control systems

D) Deterministic control systems

Correct Answer : Stochastic control systems

Explanation : Stochastic control systems are those who have unpredictable and non-repeatable response due to involvement of random parameters. Static systems is the system whose current output depends only on current input, dynamic system is a time dependent system and deterministic system’s response is predictable and repeatable.

44 .

In the field controlled motor the entire damping comes from

A) Back emf

B) Field resistance

C) Armature resistance

D) Motor friction and load

Correct Answer : Motor friction and load

45 .

In Bode plots the frequency at which two asymptotes meet is called corner frequency.

A) True

B) False

C) Can Not Say

D) None of the above

Correct Answer : True

46 .

Integral control action

A) Removes offset

B) May lead to oscillatory response

C) Both (A) and (B)

D) Neither (A) nor (B)

Correct Answer : Both (A) and (B)

47 .

Gain margin and phase margin can be determined from Bode plots as well as Nyquist plot.

A) True

B) False

C) Can Not Say

D) None of the above

Correct Answer : True

48 .

The primary function of lag compensator is to provide sufficient

A) gain margin

B) phase margin

C) both gain margin and phase margin

D) Either (A) or (B)

Correct Answer : phase margin

Explanation : It changes phase.

49 .

The polar plot of a transfer function passes through (-1, 0) point. The gain margin is

A) 1 dB

B) - 1 dB

C) infinity

D) zero

Correct Answer : zero

Explanation : When polar plot passes through (-1, 0) the system is on limit of stability and gain margin is zero.

50 .

In control systems the magnitude of error voltage

A) is very large

B) is very small

C) Neither small nor large

D) may be any value from 0 to 50 V

Correct Answer : is very small

Explanation : The error voltage is always very small. A high value of error voltage may cause instability.

51 .

The slope of log-magnitude asymptote changes by - 40 dB/ decade at a frequency ω1. This means that

A) a double pole is present

B) a pole or zero at origin is present

C) a pair of complex conjugate poles is present

D) either a double pole or a pair of complex conjugate poles is present

Correct Answer : either a double pole or a pair of complex conjugate poles is present

Explanation : A double pole or pair of complex poles result in - 40 dB/decade slope in log magnitude graph.

52 .

In a second order system, the time constant t of exponential envelopes depends

A) only on damping factor

B) only on natural frequency

C) both on damping factor and natural frequency

D) neither on damping factor nor on natural frequency

Correct Answer : both on damping factor and natural frequency

53 .

Assertion (A): Positive feedback is not used in any circuit.

Reason (R): Positive feedback leads to instability.

A) R is correct but A is wrong

A)

B) A is correct but R is wrong

B)

C) Both A and R are correct and R is correct explanation of A

C)

D) Both A and R are correct but R is not correct explanation of A

D)

Correct Answer : R is correct but A is wrong

54 .

For a quadratic factor in transfer function the phase angle is not a function of damping factor.

A) True

B) False

C) Can Not Say

D) None of the above

Correct Answer : False

Explanation : Damping ratio affects phase angle.

55 .

The current rating of dc tachogenerator is usually

A) small

B) medium

C) high

D) None of the above

Correct Answer : small

Explanation : Control systems require small current rating of components.

56 .

The effect of negative feedback on distortion and bandwidth because

A) both are increased

B) both are decreased

C) distortion is reduced and bandwidth is increased

D) distortion is increased and bandwidth is decreased

Correct Answer : distortion is reduced and bandwidth is increased

Explanation : Negative feedback increase bandwidth and reduces distortion.

57 .

The phase angle curve of G(jω) H(jω) can be drawn

A) by dividing the phase angle curves of individual factors

B) by multiplying the phase angle curves of individual factors

C) by subtracting the phase angle curves of individual factors

D) by adding the phase angle curves of individual factors

Correct Answer : by adding the phase angle curves of individual factors

58 .

The most commonly used devices for differencing and amplification, in control systems, are

A) BJT amplifiers

B) FET amplifiers

C) operational amplifiers

D) Either (A) or (B)

Correct Answer : operational amplifiers

Explanation : Op-amps are commonly used due to their several advantages.

59 .

In a second order system with a unit step input, the speed of response is high if system is

A) overdamped

B) underdamped

C) critically damped

D) undamped system

Correct Answer : underdamped

Explanation : An underdamped system with damping factor slightly less than 1 gives high speed of response.

60 .

A thermometer requires 1 minute to indicate 98% of its final response to a step input. If it is a first order system the time constant is

A) 1 minute

B) 0.5 minute

C) 0.25 minute

D) 0.1 minute

Correct Answer : 0.25 minute

Explanation :

0.98 = 1 - e^-1/T or T = 0.25 minute.

61 .

In a second order system ω_n = 10 rad/sec and ζ = 0.1, then ω_d =

A) 1 rad/sec

A)

B) 9 rad/sec

B)

C) 9.1 rad/sec

C)

D) 9.95 rad/sec

D)

Correct Answer : 9.95 rad/sec

Explaination :

W_d = ω_n√1 - ζ² = 10 (1 - 0.01)⁰⁵ = 9.95 rad/s.

62 .

A system has 12 poles and 2 zeros. Its high frequency asymptote in its magnitude plot has a slope of

A) -200 dB/decade

B) -240 dB/decade

C) -280 dB/decade

D) -320 dB/decade

Correct Answer : -200 dB/decade

Explanation : -(12 - 2) 20 or - 200 dB/decade.

63 .

Which of the following is not a necessary advantage of negative feedback system?

A) Feedback improves stability

B) Feedback improves speed of response

C) Feedback reduces the effect of external disturbances

D) Feedback reduces effect of variations in system parameters

Correct Answer : Feedback improves stability

Explanation : Feedback may or may not improve stability. Moreover feedback may also cause instability.

64 .

For type 1 system the velocity lag error is

A) Independent of gain constant

B) Inversely proportional to gain constant

C) Directly proportional to gain constant

D) Inversely proportional to bandwidth of system

Correct Answer : Inversely proportional to gain constant

65 .

The effect of adding poles and zeros can be determined quickly by

A) Nyquist plot

B) Nichols chart

C) Root locus

D) Bode plot

Correct Answer : Bode plot

66 .

Which of the following can be used as a rotating amplifier in a control system?
1. Amplidyne
2. Separately excited dc generator
3. Synchro
4. Self excited dc generator

A) 1 and 2

A)

B) 3 and 4

B)

C) 1, 2 and 3

C)

D) 1, 2, 3 and 4

D)

Correct Answer : 1 and 2

67 .

In control systems the output of sensor usually, is

A) Mechanical signal

B) Digital electrical signal

C) Analog electrical signal

D) Analog or digital electrical signal

Correct Answer : Analog or digital electrical signal

68 .

M circles are symmetrical with respect to

A) Real and imaginary axis

B) M = 1 straight line

C) M = 1 straight line and real axis

D) M = 1 straight line and imaginary axis

Correct Answer : M = 1 straight line and real axis

69 .

A system is highly oscillatory if

A) Gain margin is high

B) Gain margin is close to 1

C) Gain margin is close to 1 or phase margin is zero

D) Gain margin is high and phase margin is 180°

Correct Answer : Gain margin is close to 1 or phase margin is zero

70 .

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

A) Pressure signal to position change

B) Pressure signal to electric signal

C) Electric signal to pressure signal

D) Position change to pressure signal

Correct Answer : Pressure signal to position change

Explanation : In pneumatic control systems the control valve is used as the final control element to convert pressure signal to position change.

71 .

Consider the following statements with respect to the feedback of the control systems.

i. Feedback can improve stability or be harmful to stability if it is not properly applied.
ii. Feedback can always improve stability
iii. In many situations the feedback can reduce the effect of noise and disturbance on system performance.
iv. In general the sensitivity of the system gain of a feedback system of a parameter variation depends on where the parameter is located.

A) i, ii and iv only

A)

B) i, iii and iv only

B)

C) i, ii and iii only

C)

D) i, ii, iii and iv only

D)

Correct Answer : i, iii and iv only

Explaination : Negative feedback increases stability but not positive positive feedback reduces the stability and for this reason negative feedback systems are used.

72 .

In closed loop control system, what is the sensitivity of the gain of the overall system, M to the variation in G?

A) 1/1+GH

B) 1/1+G

C) G/1+G

D) G/1GH

Correct Answer : 1/1+GH

Explanation : The sensitivity of the control system is defined as the change in the outputs to the change in the input and senstivity of the gain of the overall system, M to the variation in G is 1/1+GH.

73 .

The input signals to control systems are not known fully ahead of time, the characteristics of control system which suddenly strain a control system are:

A) Sudden shock

B) Sudden change

C) Constant velocity and acceleration

D) All of the above

Correct Answer : All of the above

Explanation : System dynamic behavior for analysis and design is therefore judged and compared under standard test signals.

74 .

The characteristic equation of a control system is given by s(s+4)(s2+2s+s) + k(s+1) = 0. What are the angles of the asymptotes for the root loci?

A) 0°, 180°, 300°

B) 0°, 120°, 240°

C) 60°, 180°, 300°

D) 120°, 180°, 240°

Correct Answer : 60°, 180°, 300°

Explanation : P-Z = 3
Angle of asymptote = (2q+1)180°/P-Z
Hence the angles are 60°, 180°, and 300°.

75 .

Feedback control system is basically ____________

A) High pass filter

B) Low pass filter

C) Band pass filter

D) Band stop filter

Correct Answer : Low pass filter

Explanation : Low pass filter is mainly as integral controller and it is used as the controller in the system so as to increase the accuracy by reducing or proper eliminating the steady state error of the control system.

76 .

Which of the following is not a feature of a good control system?

A) Slow response

B) Good stability

C) Good accuracy

D) Sufficient power handling capacity

Correct Answer : Slow response

Explanation : A good control system is mainly negative feedback closed loop control system where the gain of system is not very high and damping is present and no oscillations are present and has fast output response.

77 .

In position control system the device used for providing rate feedback voltage is

A) potentiometer

B) tacho generator

C) synchro-transmitter

D) synchro-transformer

Correct Answer : tacho generator

Explanation : Tacho generator provides a voltage whose magnitude is proportional to speed.

78 .

Derivative control action is effective?

A) Only during steady state periods

B) During both steady state and transient state periods

C) Only during transient state periods

D) Either during steady state or during transient state periods

Correct Answer : Only during transient state periods

Explanation : Derivative of constant is zero. Hence derivative control action is not effective is steady state.

79 .

Modelling error may occur due to

A) inaccuracy of parameters

B) change of plant characteristics with time

C) neglecting the nonlinear characteristics of plant

D) Any of the above

Correct Answer : Any of the above

Explanation : Any of these may cause modelling error.

80 .

In Bode diagrams an octave is a frequency band from

A) ω1 to 2 ω1

B) ω1 to 4 ω1

C) ω1 to 8 ω1

D) ω1 to 10 ω1

Correct Answer : ω1 to 2 ω1

Explanation : An octave is a frequency band from ω1 to 2ω1

81 .

In a second order undamped system, the poles are on

A) positive real axis

B) imaginary axis

C) negative real axis

D) Either (A) or (C)

Correct Answer : imaginary axis

Explanation : If poles are on imaginary axis the response is undamped and oscillatory.

82 .

An open loop system has a forward path transfer function (42.25)/s(s + 6.5). The unit step response of the system starting from rest will have its maximum value at a time equal to

A) 0 sec

A)

B) 0.56 sec

B)

C) 5.6 sec

C)

D) infinity

D)

Correct Answer : infinity

Explaination :

83 .

Examine the following statements

1. Air and gases are compressible.
2. Air, gases and some liquids are compressible.
3. Oil can function as hydraulic fluid as well as lubricator.

Which of the above statements are correct?

A) 2 only

A)

B) 1 and 3 only

B)

C) 3 only

C)

D) 2 and 3 only

D)

Correct Answer : 1 and 3 only

84 .

Which control action is also called rate control?

A) Derivative

B) Integral

C) Proportional

D) Proportional plus integral

Correct Answer : Derivative

85 .

The gain margin for a stable system

A) has a negative decibel value

B) has a large negative decibel value

C) has a positive decibel value

D) None of the above

Correct Answer : has a positive decibel value

Explanation : For a stable system gain margin is positive. Therefore decibel value is also positive.

86 .

For overdamped systems a quadratic factor in transfer function can be replaced by two first order factors with real poles

A) True

B) False

C) Can Not Say

D) None of the above

Correct Answer : True

87 .

A synchro transmitter receiver unit is a

A) 3 phase ac device

B) 2 phase ac device

C) 1 phase ac device

D) dc device

Correct Answer : 1 phase ac device

88 .

In the given figure the input frequency f = 0.1 (1/2 p RC)

A) 0 dB

A)

B) 3 dB

B)

C) -3 dB

C)

D) 20 dB

D)

Correct Answer : 0 dB

Explaination :

X_C = 10R. Hence V₀ ⋍ V_i .

89 .

A lead compensator is basically a

A) low pass filter

B) high pass filter

C) band stop filter

D) None of the above

Correct Answer : high pass filter

Explanation :

90 .

In Bode diagram (log magnitude plot) of the factor 1/(1 + jωT) in the transfer function the log magnitude for ω << 1/T can be approximated by

A) 0 dB

A)

B) 20 log ωT dB

B)

C) -20 log ωT dB

C)

D) None of the above

D)

Correct Answer : 0 dB

91 .

Assertion (A): The part of root locus on the real axis is not dependent on the poles and zeros which are not on the real axis.

Reason (R): Poles and zeros which are not on the real axis occur in conjugate pairs

A) A is correct but R is wrong

A)

B) R is correct but A is wrong

B)

C) Both A and R are correct and R is correct explanation of A

C)

D) Both A and R are correct but R is not correct explanation of A

D)

Correct Answer : Both A and R are correct and R is correct explanation of A

92 .

For underdamped second order systems the rise time is the time required for the response to rise from

A) 5% to 95% of its final value

B) 0% to 100% of its final value

C) 10% to 90% of its final value

D) None of the above

Correct Answer : 0% to 100% of its final value

93 .

The open loop frequency response of a unity feed back system is as under

The gain margin and phase margin respectively are

A) 6 dB and 15°

A)

B) 6 dB and 25°

B)

C) 20 dB and 15°

C)

D) 20 dB and 25°

D)

Correct Answer : 6 dB and 15°

94 .

An electromechanical device which actuates a train of step angular movements in response to a train of input pulses on one to one basis is

A) LVDT

B) stepper motor

C) tacho generator

D) synchro control transformer

Correct Answer : stepper motor

95 .

Which of the following is not correct for two phase servomotor?

A) Rotor resistance is low

B) Rotor diameter is small

C) Torque speed curve is linear

D) Applied voltages are seldom balanced

Correct Answer : Rotor resistance is low

Explanation : In this motor ratio X/R is small or R is high.

96 .

DC servomotors are, generally

A) shunt field motors

B) separately excited dc motors

C) permanent magnet dc motors

D) None of the above

Correct Answer : permanent magnet dc motors

97 .

As the bandwidth increases, the cost of components

A) generally decreases

B) does not change

C) may increase or decrease

D) generally increases

Correct Answer : generally increases

98 .

A conditionally stable system has

A) one phase crossover frequency

B) two phase crossover frequencies

C) one or more phase crossover frequencies

D) two or more phase crossover frequencies

Correct Answer : two or more phase crossover frequencies

99 .

If Nyquist plot has a encirclement of (-1 + jo) point, the system is stable if

A) there is no zeros of G(s) H(s) in right-half plane

B) there are no poles of G(s) H(s) in right-half plane

C) there is one pole of G(s) H(s) in right-half plane

D) None of the above

Correct Answer : there are no poles of G(s) H(s) in right-half plane

100 .

In a pneumatic bellows

A) the input surface and output surface are flat but the side walls are corrugated

B) the input surface, output surface and side walls are corrugated

C) the input surface and side walls are flat but the output surface is corrugated

D) the input surface and output surface are corrugated but the side walls are flat

Correct Answer : the input surface and output surface are flat but the side walls are corrugated

101 .

Generally a servomotor operates at

A) high torque and low speed

B) high torque and high speed

C) low torque and high speed

D) low torque and low speed

Correct Answer : low torque and high speed

102 .

If C is thermal capacitance, m is mass of liquid and c is specific heat, then

A) C = mc

B) m = cC

C) v

D) C = (mc)2

Correct Answer : C = mc

103 .

The ac motor used in servo applications is

A) single phase induction motor

B) two phase induction motor

C) Three phase induction motor

D) v

Correct Answer : two phase induction motor

104 .

Optical encoders most commonly used in control systems are

A) absolute encoders

B) secondary encoders

C) incremental encoders

D) None of the above

Correct Answer : incremental encoders

105 .

The shape of torque-speed curve of a two phase servo- motor mostly depends on

A) ratio of rotor reactance to rotor resistance

B) magnitude of stator voltages

C) ratio of stator reactance to rotor resistance

D) ratio of rotor reactance to rotor resistance and also the ratio of stator reactance to stator resistance

Correct Answer : ratio of rotor reactance to rotor resistance

106 .

In a lag network the input frequency is 100 fc where fc is critical frequency. The voltage gain is

A) 0 dB

B) -20 dB

C) -40 dB

D) -60 dB

Correct Answer : -40 dB

107 .

The correct sequence of events to improve system stability is

A) reduce gain, use negative feedback, insert derivative action

B) insert derivative action, use negative feedback, reduce gain

C) reduce gain, insert derivative feedback, use negative feed back

D) use negative feedback, reduce gain, insert derivative action

Correct Answer : use negative feedback, reduce gain, insert derivative action

108 .

Which of the following represents constant magnitude locus for M = 1?

A) x = 0

B) x = -0.5

C) x² + y² = 1

D) (x + 1)² + y² = 1

Correct Answer : x = -0.5

109 .

Assertion (A): A synchro control transformer has nearly constant impedance across its rotor terminals.

Reason (R): Rotor of a synchro control transformer is cylindrical so as to give uniform flux distribution.

A) A is correct but R is wrong

A)

B) R is correct but A is wrong

B)

C) Both A and R are correct but R is not correct explanation of A

C)

D) Both A and R are correct and R is correct explanation of A

D)

Correct Answer : Both A and R are correct and R is correct explanation of A

110 .

A major part of the automatic control theory applies to the

A) Casual systems

B) Non-linear systems

C) Linear Time invariant systems

D) Time variant systems

Correct Answer : Linear Time invariant systems

Explanation : A linear time invariant (LTI) system provides the same output for the same input irrespective of when input is given. LTI systems are also used to predict the system's long term behavior.

111 .

Traffic light system is the example of :

A) Open-loop system

B) Closed-loop system

C) Both (A) and (B)

D) None of the above

Correct Answer : Open-loop system

Explanation : The traffic lamp will glow according to the set timing and sequence and is time-dependent. The sequence and time are controlled by relays that work on the pre-programmed time. It does not depend upon the rush of the road.

112 .

The negative feedback closed-loop system was subjected to 15V. The system has a forward gain of 2 and a feedback gain of 0.5. Determine the output voltage and the error voltage.

A) 6V, 5V

A)

B) 5V, 10V

B)

C) 15V, 10V

C)

D) 15V, 7.5V

D)

Correct Answer : 15V, 7.5V

Explaination :

113 .

The Static system can be defined as :

A) Output of the system depends on future inputs.

B) Output of the system depends only on the present input.

C) Output of a system depends only on the received inputs.

D) Output of a system depends on the present as well as past input.

Correct Answer : Output of the system depends only on the present input.

Explanation : Static systems do not have any feedback system. Hence, the output depends only on the present input.

114 .

Determine the transfer function of the given system:

A) G1G2G3 / (1 + G1G2G3H1)

A)

B) G1 G2G3/ (1 + G1G2G3H2H1)

B)

C) G1G2G3/ (1 + H2G2G3 + G2G1H1)

C)

D) G1G2G3 / (1 + G1G2G3H1 + G1G2G3H2)

D)

Correct Answer : G1G2G3/ (1 + H2G2G3 + G2G1H1)

Explaination : We will first shift the H1 block after G3

The shifting of a take-off point will make the block as: H1/ G3

Block G2 and G3 are in cascade. The equivalent block will be the product of these two (G2G3).

The gain for that block will be:

G2G3/ (1 + H2G2G3)

As shown, G1 is in cascade, the transfer function of the above system will be:

C(s)/R(s) = [G1G2G3/ (1 + H2G2G3)]/ [1 + G1G2G3/ (1 + H2G2G3) x H1/G3

C(s)/R(s) = G1G2G3/ (1 + H2G2G3 + G2G1H1)

115 .

Loop gain is equal to:

A) Product of all branch gains in a loop

B) Summation of all branch gains in a loop

C) Sum of all branch gains while traversing the forward path

D) Product of all branch gains while traversing the forward path

Correct Answer : Product of all branch gains while traversing the forward path

Explanation : According to Mason's Gain formula, the transfer function can be calculated as : T(s) = C(s)/R(s)

116 .

If the characteristic equation of the closed loop system is s^2 + 2s + 2 = 0, then the system is:

A) Underdamped

B) Undamped

C) Over damped

D) Critically damped

Correct Answer : Underdamped

Explanation : The given equation is: s^2 + 2s + 2 = 0

It is a second-order differential equation. The Laplace transform of a standard form of a second-order differential equation is:

Thus, the system is underdamped.

117 .

In a two phasor servomotor, the direction of rotation of the rotating field depends on

A) Magnitudes of voltages applied to the two stator windings

B) Both magnitude and phase relationship of voltages applied to the two stator windings

C) Phase relation of voltages applied to the two stator windings

D) None of the above

Correct Answer : Phase relation of voltages applied to the two stator windings

118 .

Which of the following is open loop system?

A) Aqualing

B) Wind screen wiper

C) Respiratory system of animal

D) System for controlling antirocket missiles

Correct Answer : Wind screen wiper

119 .

The poles with greater displacement from the real axis correspond to

A) Stable response

B) Higher frequencies of oscillations

C) Unbounded output

D) Lower frequencies of oscillations

Correct Answer : Higher frequencies of oscillations

120 .

The sensor generally used in incremental optical encoder is

A) LED

B) LCD

C) Either (A) or (B)

D) Photodiode

Correct Answer : Photodiode

121 .

In force current analogue, mechanical mobility is analogous to

A) Impedance Z

B) Admittance Y

C) Reactance X

D) Conductance G

Correct Answer : Impedance Z

122 .

Nichols chart consists of

A) Constant magnitude loci

B) Constant phase angle loci

C) Either (A) or (B)

D) Magnitude and phase angle loci in log-magnitude versus phase diagram

Correct Answer : Magnitude and phase angle loci in log-magnitude versus phase diagram

123 .

The open loop transfer function of the feedback control system is given by G(s) = K(s+3)/s(s+4)2(s+5)(s+6). The number of asymptotes and the centroid of asymptotes of the root loci of closed loop system is?

A) 4 and (-4,0)

A)

B) -4 and (-4,0)

B)

C) 3 and (-12,0)

C)

D) -3 and (-12,0)

D)

Correct Answer : 4 and (-4,0)

Explaination : Number of Poles = 5
Zeroes = 1
Asymptotes = P-Z = 4
Centroid = Σreal part of open loop pole-Σreal part of open loop zeroes/P-Z
Centroid = -4-4-5-6+3/4 = -4.

124 .

With negative feedback in a closed loop control system, the system sensitivity to parameter variation:

A) Increases

B) Decreases

C) Becomes zero

D) Becomes infinite

Correct Answer : Decreases

Explanation : Sensitivity is defined as the change in the output with respect to the change in the input and due to negative feedback reduces by a factor of 1/(1+GH).

125 .

The open loop transfer function of a plant is given as, G(s) = 1/s²-1. If the plant is operated in unity feedback configuration, then the lead compensator that can stabilize the control system is:

A) 10(s+4)/(s+2)

A)

B) 10(s+2)/(s+10)

B)

C) 10(s-1)/(s+2)

C)

D) 10(s+2)/(s+10)

D)

Correct Answer : 10(s-1)/(s+2)

Explaination : G(s) = 1/(s-1)(s+1)
The lead compensator C(s) should stabilize the plant as it is similar to the differentiator and the tendency of it is to stablize the system by increasing the damping hence remove the first term so only option 10(s-1)/(s+2) satisfies.

126 .

Controllers play which of the following role in the control system?

A) They amplify the signals going to the actuator

B) They try to reduce steady state error optimizes overshoot

C) They act on the error signal coming out of the summing junction and output a suitable to the actuator

D) All of the above

Correct Answer : They amplify the signals going to the actuator

Explanation : Controller amplify the signals going to the actuator and they are of many types as proportional, integral, derivative some combinational controller a combination of two controllers and combination of all the controllers.

127 .

What is the relation between output response and input signal in closed loop system?

A) Parabolic

B) Nonlinear

C) Linear

D) Exponential

Correct Answer : Linear

Explanation : Due to the linearizing effect of the feedback the relation between output response and the input signal in closed loop system is linear.

128 .

Which of the following is the input of a controller?

A) Sensed signal

B) Error signal

C) Desired variable value

D) Signal of fixed amplitude not dependent on desired variable value

Correct Answer : Error signal

Explanation : Controller is the block in the control system that control the input and provides the output and this is the first block of the system having the input as the error signal.

129 .

For a second order system the damping factor is varied from 0 to 1. The locus of poles is

A) a semi circle

B) a circle

C) a straight line on real axis

D) a straight line on imaginary axis

Correct Answer : a semi circle

130 .

In a synchro transmitter, which coil acts as primary?

A) Stator

B) Rotor

C) Tertiary

D) Partly rotor and partly stator

Correct Answer : Rotor

131 .

In force voltage analogy the quantity analogous to spring constant K is

A) C

B) L

C) R

D) 1/C

Correct Answer : 1/C

132 .

Time rate of change in heat energy is analogous to

A) charge

B) voltage

C) current

D) voltage gradient

Correct Answer : current

133 .

I-PD controlled system has

A) I, P and D actions in forward path

B) I, P and D actions in feedback path

C) I action in forward path but P and D action in feedback path

D) I action in feedback path but P and D actioins in forward path

Correct Answer : I action in forward path but P and D action in feedback path

134 .

Integral error compensation changes a second order system to

A) first order system

B) third order system

C) fourth order system

D) None of the above

Correct Answer : third order system

135 .

An ac tachometer has a drag cup construction so that

A) rotor inertia is low

B) rotor body is conducting

C) rotor is easy to fabricate

D) Both (A) and (B)

Correct Answer : Both (A) and (B)

136 .

The addition of a zero to the open loop transfer function

A) pulls the root locus to the left and makes the system more stable

B) pulls the root locus to the right and makes the system less stable

C) Either (A) or (B)

D) Neither (A) nor (B)

Correct Answer : pulls the root locus to the left and makes the system more stable

137 .

If a zero is added to a second order underdamped system

A) the peak overshoot is decreased

B) the peak overshoot remains unchanged

C) the peak overshoot is increased

D) Both (A) and (B)

Correct Answer : the peak overshoot is increased

138 .

PID controlled system has

A) All the three (i.e., P, I and D) actions in forward path

B) All the three (i.e., P, I and D) actions in feedback path

C) P and I actions in feedback path and actions in forward path

D) P and I actions in forward path and D action in feedback path

Correct Answer : P and I actions in forward path and D action in feedback path

139 .

In case of synchro error detector the electrical zero position of control transformer is obtained when angular displacement between rotors is

A) 180°

B) 90°

C) 45°

D) zero

Correct Answer : 90°

140 .

The transfer function of a system is given as 81/ (s^2 + 16s + 81). Find the undamped natural frequency, damping ratio, and peak time for a unit step input.

A) 9, 0.889, 0.762

B) 9, 0.559, 0.762

C) 9, 0.889, 0.187

D) 9, 0.667, 0.187

Correct Answer : 9, 0.889, 0.762

141 .

The impulse response of an RL circuit is:

A) Step function

B) Parabolic function

C) Decaying exponential function

D) Rising exponential function

Correct Answer : Decaying exponential function

Explanation : The RL circuit comprises of the resistor and inductor connected in series.

The equation can be written as:

1 = RI(s) + sLI(s)

1 = I(s) [R + sL]

I(s) = 1 / (R +sL)

Taking the inverse Laplace, we get:

The equation clearly depicts that the impulse response is a decaying exponential function.

142 .

Calculate the poles and zeroes for the given transfer function G(s) = 5 (s + 2)/ (s^2 + 3s + 2)

A) 2, (-1, 2)

B) -2, (-1, -2)

C) 2, (1, 2)

D) -2, (1, -2)

Correct Answer : -2, (-1, -2)

Explanation : The zeroes can be calculated by equating the numerator to zero:

5 (s + 2) = 0

5s + 10 = 0

5s = -10

s = -2

The poles can be calculated by equating the denominator to zero:

s^2 + 3s + 2 = 0

s^2 + 2s + s + 2 = 0

s (s + 2) + 1 (s + 2) = 0

(s + 1) (s + 2) = 0

s = -1, -2

143 .

The number of roots in the left half of the s-plane of the given equation s^3 + 3s^2 + 4s + 1 = 0 is:

A) One

B) Two

C) Three

D) Zero

Correct Answer : Three

Explanation : The given characteristic equation is: s^3 + 3s^2 + 4s + 1 = 0.

To find the number of roots, we need to create a Routh table, as shown below:

There are no roots and no significant changes in the RHS plane, as shown in the above table. Hence, all three roots lie in the LHS plane.

144 .

A system with the polynomial s^4 + 5s^3 + 3s^2 + 6s + 5 = 0 is:

A) Unstable

B) Stable

C) In equilibrium

D) Marginally stable

Correct Answer : Unstable

Explanation : The given characteristic equation is: s^4 + 5s^3 + 3s^2 + 6s + 5 = 0. We first need to find the roots by creating the Routh's array table.

Routh's array table is shown below:

In the first column of the above table, we have two sign changes. It means that two roots are in the RHS plane. Hence, the system is unstable.

145 .

If s^3 + Ks^2 + 5s + 10 = 0, the root of the feedback system's characteristic equation is said to be critically stable. Then, the value of K will be:

A) 1

B) 2

C) 3

D) 4

Correct Answer : 2

Explanation : For the above equation, we need to find the roots by creating the Routh's array table. The given equation is: s^3 + Ks^2 + 5s + 10

The table is given below:

For the system to be critically stable, we will put (5K -10)/K = 0

5K - 10 = 0

5K = 10

K = 2

The value of K for which the system is said to be critically stable is 2.

146 .

Magnetic amplifier is used for

A) Current amplification

B) Voltage amplification

C) Frequency amplification

D) Power amplification

Correct Answer : Power amplification

147 .

Which control action can never be used alone?

A) Derivative

B) Integral

C) Proportional

D) None of the above

Correct Answer : Derivative

148 .

In force current analogy, displacement x is analogous to

A) Charge

B) Voltage

C) Magnetic flux linkage

D) Electrostatic energy

Correct Answer : Magnetic flux linkage

149 .

If the poles lie in second quadrant, damping ratio is

A) 1

B) less than 1

C) zero

D) more than 1

Correct Answer : less than 1

150 .

If poles lie in first quadrant, damping ratio is

A) 1

B) Zero

C) less than 1

D) More than 1

Correct Answer : less than 1

151 .

In a simple on-off controller with differential gap, the magnitude of differential gap determines

A) The level of accuracy

B) The life of controller

C) Both (A) and (B)

D) Neither (A) nor (B)

Correct Answer : The life of controller

152 .

The distance of poles from origin depends on

A) Uqndamped natural frequency

B) Damping ratio

C) Both (A) and (B)

D) Neither (A) nor (B)

Correct Answer : Uqndamped natural frequency

153 .

The permanent magnet field system of brushless dc servo- motor is generally on

A) Rotor

B) Stator

C) Partly on stator and partly on rotor

D) Either (A) or (B)

Correct Answer : Rotor

154 .

For any transfer function, the constant phase angle loci are

A) A family of circles

B) A family of straight lines

C) Either (A) or (B)

D) Neither (A) nor (B)

Correct Answer : A family of circles

155 .

The addition of a pole to the open loop transfer function pulls the root locus

A) To the right

B) To the left and making the system more stable

C) Towards right or left depending on the position of new pole

D) None of the above

Correct Answer : To the right

156 .

Which of the following are the not characteristics of the closed loop systems?

A) It does not involve I/O measurements

B) It does not compensate for disturbance

C) It reduces the sensitivity of plant-parameter variations

D) It does not have the ability to control the system transient response

Correct Answer : It does not have the ability to control the system transient response

Explanation : Feedback refers to the comparison of the final output to the desired output at respective input so as to get accurate and error free result and in the system improves the transient response of the system.

157 .

A control system whose step response is -0.5(1+e^-2t) is cascaded to another control block whose impulse response is e^-t. What is the transfer function of the cascaded combination?

A) 1/(s+1)s

A)

B) 1/(s+3)

B)

C) 1/(s+2)(s+1)

C)

D) 0.5/(s+1)(s+2)

D)

Correct Answer : 1/(s+2)(s+1)

Explaination : Laplace transform is the transformation that transforms the time domain into frequency domain and of both the cascaded systems are 1/(s+1)(s+2).

158 .

Effect of feedback on sensitivity is minimum in:

A) Open loop control system

B) Closed loop control system

C) Open and closed loop control systems

D) None of the above

Correct Answer : Closed loop control system

Explanation : Sensitivity is defined as the change in output with respect to change in parameter or input and for a good control system the sensitivity must be less and in closed loop control system it gets reduced by the factor of 1/(1+GH).

159 .

Which of the motions in actuators are preferred?

A) Stationary

B) Rotary

C) Translator

D) Non-Stationary

Correct Answer : Rotary

Explanation : An actuator in a control system perform variety of task in hydraulic, pneumatic and electrical system but majorly they are all controlling rotary motions.

160 .

Sampling is necessary ____________

A) Automated control system

B) In complex control system

C) Non automated control system

D) Where high accuracy is required

Correct Answer : Where high accuracy is required

Explanation : Sampling is the process where the continuous systems are converted into discrete time systems with the help of zero order hold of the signal and sampling is necessary where high accuracy is needed.

161 .

A particular control system yielded a steady state error of 0.20 for unit step input. A unit integrator is cascaded to this system and unit ramp input is applied to this modified system. What is the value of steady-state error for this modified system?

A) 0.10

A)

B) 0.15

B)

C) 0.25

C)

D) 0.20

D)

Correct Answer : 0.25

Explaination : The integrator is similar to the phase lag system and it is used to reduce or eleminate the steady state error and when it is cascaded with the ramp input hence the acceleration error constant is calculated which is equal to 0.25.

162 .

DC tachogenerator can be used in

A) Speed control system

B) Position control system

C) Both (A) and (B)

D) Neither (A) nor (B)

Correct Answer : Both (A) and (B)

163 .

If any term in the first column of a Routh array becomes zero, then

A) Routh criterion can be used by substituting a small positive number for zero and completing the array

B) Routh criterion cannot be used to determine stability

C) Routh criterion can be used by substituting a big positive number for zero and completing the array

D) Routh criterion can be used by substituting a small negative number for zero and complet-ing the array

Correct Answer : Routh criterion can be used by substituting a small positive number for zero and completing the array

164 .

Temperature is analogous to

A) Flux

B) Voltage

C) Charge

D) None of the above

Correct Answer : Voltage

165 .

Which of the following is used to obtain output position in a position control system?

A) Synchro

B) Load cell

C) Thermistor

D) Strain gauge

Correct Answer : Load cell

166 .

A conditionally stable system is stable for the value of gain between two critical values. It is unstable if

A) The gain is increased beyond upper critical value

B) The gain is decreased below lower critical value

C) Both (A) and (B)

D) Neither (A) nor (B)

Correct Answer : Both (A) and (B)

167 .

Which dc servomotor requires strongest permanent magnet?

A) Slotted armature

B) Surface wound armature

C) Both (A) and (B)

D) Surface wound with stationary rotor

Correct Answer : Surface wound with stationary rotor

168 .

Find the number of asymptotes for the given open-loop transfer function of a unity feedback system:

G(s) = ((s + 2) (s+3) (s + 4)) / ((s + 5) (s+6) (s + 1))

A)

B) 1

B)

C) 2

C)

D) 3

D)

Correct Answer : 0

Explaination : The number of asymptotes in a given system is equal to the number of branches approaching infinity. So, the formula to calculate the number of asymptotes is P -Z. Here, P and Z represent the poles and zeroes.

We know that poles and zeroes are calculated by equating the denominator and numerator to zero. So, for the given open-loop transfer function, we get:

P = 3

Z = 3

So, the number of zeroes at infinity = 3 - 3 = 0

169 .

An open loop transfer function is given by G(s) = K (s + 1) / (s + 4)(s^2 + 3s + 2). It has:

A) One zero at infinity

B) Two zeroes at infinity

C) Three zeroes at infinity

D) None of the above

Correct Answer : Two zeroes at infinity

Explanation : The formula to calculate a number of zeroes at infinity is P - Z. Here, P and Z are the number of poles and zeroes in a given transfer function.

We know that poles are calculated by equating the denominator to zero, and zeroes are calculated by equating the numerator to zero. So, for the above given transfer function, we get:

P = 3

Z = 1

So, the number of zeroes at infinity = 3 - 1 = 2

170 .

The centroid in the root locus is a point where

A) The asymptotes cross the real axis.

B) The branches of the root locus tend to infinity.

C) The branches of the root locus terminate on the real axis.

D) The branches of the root locus intersect with the imaginary axis.

Correct Answer : The asymptotes cross the real axis.

Explanation : Centroid is defined as a common point where all the asymptotes intersect on the real axis. The value of centroid is always real. But, it can be located either on the positive or negative real axis.

171 .

Calculate the centroid for the given system:

G(s) = K / [(s + 1) (s + 4 + 4j) (s + 4 - 4j)]

A) - 1.47

A)

B) -2

B)

C) -2.66

C)

D) -3

D)

Correct Answer : -3

Explaination : We will first calculate the number of branches approaching infinity and then the asymptotes. With the help of asymptotes, we will calculate the value of centroid.

The given transfer function of the system is G(s) = K / [(s + 1) (s + 4 + 4j) (s + 4 - 4j)].

The number of asymptotes is equal to the number of branches approaching infinity. There are no zeroes but three poles.

So, P - Z = 3

Let's calculate the value of the poles by equating the denominator equal to zero. We get:

Poles located at: -1,

The angle of asymptotes is calculated by:

Θ = (2q + 1) 180 / (P - Z)

Here, q = 0, 1, 2…

The number of asymptotes is equal to the number of branches approaching infinity.

So, we will calculate the asymptotes at value 0, 1, and 2.

For q = 0,

Θ=180⁄3=60degrees

For q = 1,

Θ=(2+1) 180⁄3=180degrees

For q = 2,

Θ=(4+1) 180⁄3=300degrees

Centroid is defined as a common point where all the asymptotes intersect on the real axis.

σ= / (P - Z)

σ= (- 1 - 4 - 4 - 0) / 3

σ=(-9)⁄3

σ=-3

172 .

In a bode-plot of a unity feedback control system, the value of phase of G(jw) at the gain cross over frequency is -115 degrees. The phase margin of the system is:

A) -57.5 degrees

A)

B) -65 degrees

B)

C) 65 degrees

C)

D) 115 degrees

D)

Correct Answer : 65 degrees

Explaination : The phase margin can be calculated as 180 +

Where,

∅ is the phase of G(jw) at the gain cross over frequency.

So, phase margin = 180 + (-115)

= 180 - 115

= 65 degrees

173 .

The gain margin of a second-order system is

A) Zero

B) One

C) Two

D) Infinite

Correct Answer : Infinite

Explanation : The gain margin indicates the additional gain provided to the system without affecting its stability.

The total phase shift of a second-order system is approximately equal to 180 degrees, which leads to the infinite frequency. Thus, the gain margin is also infinite.

174 .

Determine the gain margin of the given open-loop feedback control system: G(s)H(s) = 1 / [(s + 1) ^3]

A) 2

B) 4

C) 8

D) 32

Correct Answer : 8

Explanation :

The given open-loop feedback control system is: G(s)H(s) = 1 / [(s + 1) ^3]

The phase angle for the cross-over frequency can be calculated by:

-3 tan^-1 ω=-180°

We get the value of ω=√3

Now, the gain margin is the magnitude of the transfer function, as shown below:

= 1 / |G(s)H(s)| = |(j√3+1³|

= 8

175 .

The corner frequency in the Bode plot is :

A) The frequency at which the two asymptotes intersect.

B) The frequency at which the two asymptotes meet.

C) The frequency at which bode plot slope is 0 dB /decade.

D) The frequency at which bode plot slope is -10 dB /decade.

Correct Answer : The frequency at which the two asymptotes meet.

Explanation : The frequency at which the two asymptotes in the Bode plot meet is termed as corner frequency.

176 .

The slope of log magnitude curve changes by - 40 dB/decade at a certain frequency and the error between asymptote and actual curve is positive. This means that

A) a double pole is present

A)

B) a pair of complex conjugate poles is present

B)

C) Either (A) or (B)

C)

D) Neither (A) nor (B)

D)

Correct Answer : a pair of complex conjugate poles is present

177 .

A system has high gain and phase margin. The system is

A) sluggish

B) oscillatory

C) very stable

D) very stable and sluggish

Correct Answer : very stable and sluggish

178 .

A proportional controller is basically

A) an amplifier with adjustable gain

B) an integrating amplifier

C) an amplifier with infinite gain

D) an amplifier with almost zero gain

Correct Answer : an amplifier with adjustable gain

179 .

The purpose of series quadrature windings in amplidyne is to

A) increase the gain

B) increase response time

C) reduce commutation difficulties

D) neutralize the effect of armature reaction

Correct Answer : neutralize the effect of armature reaction

180 .

In classical analogue, torque is analogous to

A) voltage

B) charge

C) current

D) voltage gradient

Correct Answer : voltage

181 .

The given figure shows a constant current source driving a parallel RC circuit. It is equivalent to

A) a lag network

A)

B) a lead network

B)

C) a lag-lead network

C)

D) None of the above

D)

Correct Answer : a lag network

182 .

Which of the following are applications of position control systems?

A) Radar tracking system

B) Missile guidance of ships

C) Control of sheet and metal thickness in hot rolling mill

D) All of the above

Correct Answer : All of the above

183 .

For a second order system delay time t_d is the time required to reach

A) the final value for the very first time

A)

B) half the final value for the very first time

B)

C) 90% of the final value for the very first time

C)

D) None of the above

D)

Correct Answer : half the final value for the very first time

184 .

Coulomb friction is

A) the force of sliding friction between dry surfaces

B) the force required to initiate motion between two contacting surfaces

C) the force of friction between moving surfaces separated by viscous fluid

D) All of the above

Correct Answer : the force of sliding friction between dry surfaces

185 .

The damping ratio of a pair of complex poles when expressed in terms of angle θ measured from jω axis equal to

A) cos θ

B) sin θ

C) tan θ

D) cot θ

Correct Answer : sin θ

186 .

Friction forces acts in a direction

A) same as that of velocity

B) at right angle to that of velocity

C) opposite to that of velocity

D) partly opposite and partly at right angle to the direction of velocity

Correct Answer : opposite to that of velocity

187 .

In some on-off controllers a differential gap is provided

A) to make the manufacture process easier

B) to prevent too often frequent operation of controller

C) Both (A) and (B)

D) Neither (A) nor (B)

Correct Answer : to prevent too often frequent operation of controller

188 .

A reactance function

A) has a pole at origin

B) has a zero at origin

C) may have a pole or zero at origin

D) has a pole or zero at origin and a pole or zero at infinity

Correct Answer : has a pole or zero at origin and a pole or zero at infinity

189 .

While forming Routh's array, the situation of a row of zeros indicates that the system

A) is stable

B) is unstable

C) has symmetrically located roots

D) is not sensitive to variations in gain

Correct Answer : has symmetrically located roots

190 .

The frequency at which phase angle is 180° is called

A) phase crossover frequency

B) stability limit frequency

C) gain margin frequency

D) frequency of limited stability

Correct Answer : phase crossover frequency

191 .

In a mechanical accelerometer, the steady state displacement is a measure of

A) constant input velocity

B) constant input acceleration

C) Either (A) or (B)

D) Neither (A) nor (B)

Correct Answer : constant input acceleration

192 .

For a stable system having two or more gain crossover frequencies the phase margin is measured

A) at highest gain crossover frequency

B) at lowest gain crossover frequency

C) at the gain crossover frequencies

D) None of the above

Correct Answer : at highest gain crossover frequency

193 .

In a second order system, peak overshoot is independent of

A) damping factor

B) natural frequency

C) both damping factor and natural frequency

D) neither damping factor nor natural frequency

Correct Answer : natural frequency

194 .

Power handling capacity of wire wound potentiometer used in control systems is about

A) 100 W

B) 25 W

C) 5 W

D) 0.1 W

Correct Answer : 5 W

195 .

The GM of a unity feedback system with the transfer function 1/ (s + 5)^3 is:

A) 10 dB

B) 30 dB

C) 40 dB

D) 60 dB

Correct Answer : 60 dB

196 .

The most powerful controller is :

A) PI Controller

B) PD controller

C) PID Controller

D) None of the above

Correct Answer : PID Controller

Explanation : The PID is the combination of proportional, integral, and derivate control modes. Such a combination makes it the most powerful controller.

197 .

The controller required to handle fast process load changes is :

A) PD controller

B) PI Controller

C) PID Controller

D) None of the above

Correct Answer : PD controller

Explanation : The Proportional Derivative controller is preferred to handle fast process load changes.

198 .

Find the phase shift provided by the lead compensator for a given transfer function G(s) = (1 + 6s)/ (1 + 2s)

A) 15 degrees

B) 30 degrees

C) 45 degrees

D) 60 degrees

Correct Answer : 30 degrees

Explanation :

199 .

The sum of the Eigenvalues in the given matrix is :

A) Sum of the elements of any row

B) Sum of the elements of any column

C) The sum of all non-zero components in the matrix

D) Sum of the principal diagonal elements

Correct Answer : Sum of the principal diagonal elements

Explanation : The sum of Eigenvalue of a given matrix is generally called the trace of that matrix. The trace of a matrix is the sum of the diagonal elements of a matrix.

200 .

A lag compensator provides attenuation in

A) low frequency range

B) very low frequency range

C) high frequency range

D) None of the above

Correct Answer : high frequency range

201 .

A stepper motor is essentially

A) a synchronous motor

B) dc motor

C) induction motor

D) Either (B) or (C)

Correct Answer : a synchronous motor

202 .

The root locus branches

A) start from open loop poles and terminate at zeros

B) start from open loop zeros and terminate at poles

C) may start from pole or zero and terminate at another pole or zero

D) None of the above

Correct Answer : start from open loop poles and terminate at zeros

203 .

In force voltage analogy, displacement is analogous to

A) voltage

B) charge

C) current

D) None of the above

Correct Answer : charge

204 .

For stable network the real parts of poles and zeros of driving point functions must be

A) zero

B) positive

C) negative

D) negative or zero

Correct Answer : negative or zero

205 .

If Z is the number of zeros of 1 + G(s) H(s) in the right half s plane. N is the number of clockwise encircle elements of (-1 + jo) point. P is the number of poles of G(s) H(s) in right half s plane. The Nyquist stability criterion can be expressed as

A) Z = PN

A)

B) Z = P/N

B)

C) Z = N - P

C)

D) Z = N + P

D)

Correct Answer : Z = N + P

206 .

In a synchro transmitter

A) input is rotor voltage and output is angular position of rotor shaft

B) input is angular position of rotor shaft and output is rotor voltage

C) input is angular position of rotor shaft and output is stator voltages

D) input is stator voltages and output is angular position of shaft input is rotor voltage and output is angular position of rotor shaft

Correct Answer : input is angular position of rotor shaft and output is stator voltages

207 .

The polar plot of G(jω) = 1/jω is

A) positive real axis

B) negative real axis

C) positive imaginary axis

D) negative imaginary axis

Correct Answer : negative imaginary axis

208 .

The resolution of a wire wound potentiometer is about

A) 5%

B) 1%

C) 0.1%

D) 0.001%

Correct Answer : 0.1%

209 .

The response to sinusoidal excitation can be found by

A) setting s = jω in the network function

B) setting s = -jω in the network function

C) taking inverse transform of network function

D) None of the above

Correct Answer : setting s = jω in the network function

210 .

For a quadratic factor in denominator of transfer function the phase angle at corner frequency (in Bode phase angle plot)

A) is +90°

B) is -90°

C) depends on the damping factor

D) None of the above

Correct Answer : is -90°

ECE : Automatic Control Systems MCQs with Answers