22531 Control System MCQs with Answers
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Program: Diploma in E&Tc engineering Program Code:- EJ
Scheme:-I Semester:- 5
Course:- Control System & PLC (CSP) Course Code:- 22531
{tocify} $title={Unit Wise MCQs👇}
01 – Basic of control system Marks:-12
Content of Unit:-
1.1 Basics of control systems
Basic block diagram & classification
1.2 Open loop & Close loop control system details & their comparison
Linear & Nonlinear control systems, Time varying & Time in varying control system details
1.3 Transfer Functions: RC, LC & RLC circuits – differential equations & transfer functions along with analysis
1.4 Block diagram reduction technique
1 The overall transfer function of two blocks in parallel are :
a) Sum of individual gain
b) Product of individual gain
c) Difference of individual gain
d) Division of individual gain
Answer: - Option A
2. Transfer function of the system is defined as the ratio of Laplace output to Laplace input
considering initial conditions________
a) 1
b) 2
c) 0
d) infinite
Answer: - Option A
Explanation: - Initials conditions should be zero for calculation
3. In regenerating the feedback, the transfer function is given by
a) C(s)/R(s)=G(s)/1+G(s)H(s)
b) C(s)/R(s)=G(s)H(s)/1-G(s)H(s)
c) C(s)/R(s)=G(s)/1+G(s)H(s)
d) C(s)/R(s)=G(s)/1-G(s)H(s)
Answer: - Option A
4 By equating the denom inator of tr ansfer func tion to zero , which am ong the following will be
obtained?
a) Poles
b) Zeros
c) Both a and b
d) None of the above
Answer: - Option A
Explanation: - Poles and Zeros of a transfer function are the frequencies for which the value of the
denominator and numerator of transfer function becomes zero respectively.
5 The overall transfer fun ction from block diagr am reductio n for casca ded blocks is :
a) Sum of individual gain
b) Product of individual gain
c) Difference of individual gain
d) Division of individual gain
Answer: - Option b
6 The output o f the feedb ack contr ol system must be a function o f:
a) Reference input
b) Reference output
c) Output and feedback sig nal
d) Input and feedback signal
Answer: - Option d
Explanation: In closed loop control systems, output is fed back to the input. So, the control action is
dependent on the desired output.
7 Which amon g the follo wing is no t an advan tage of an open loop system?
a) Simplicity in construction & design
b) Easy maintenance
c) Rare problems of stabili ty
d) Requirement of system recalibratio n from time to time
Answer: - Option d
Explanation: Open loop system requires calibration time to time.
8. Associative law for summing point is applicable only to those summing points which are
__________connected to each other.
a) Directly
b) Indirectly
c) Orthogonally
d) Diagonally
Answer: - Option a
Explanation:
9 In block diag ram repre sentation, what do th e lines co nnecting th e blocks, known as?
a) Branches
b) Nodes
c) Datums
d) Sources
Answer: - Option d
Explanation: Arrows indicate the direction of the flow of signals and lines are called as sources.
10 At summing point, mor e than one signal ca n be added or _____ ____
a) Subtracted
b) Multiplied
c) Both a and b
d) None of the above
Answer: - Option a
Explanation: Summing point is used to add or subtract two signals.
11 Which of the f ollowing is not the feat ure of mod ern control system?
a) Quick response
b) Accuracy
c) Correct powe r level
d) No oscillation
Answer: - Option d
12 For a good co ntrol system the speed of respon se and stab ility must b e high and for the slow and
sluggish response is not used and undesirable.
a) The principle of homogeneity and superposition are applied to:
b) Linear time invariant systems
c) Nonlinear time invariant systems
d) Linear time variant systems
Nonlinear time invariant systems
Answer: - Option d
13 Superposition theorem st ates that fo r two signa ls additivity and homo geneity property must be satisfied and that is applicable for the LTI systems.
When deriving the transfer function of a linear element
a) Both initial conditions and loading are taken into account
b) Initial conditions are taken into account but the element is assumed t o be not loaded
c) Initial conditions are assumed to be zero but loading is taken into account
d) Initial conditions are assumed to be zero and the element is assumed to be not loaded
Answer: - Option c
Explanation: When deriving the transfer function of a linear element only initial conditions are
assumed to be zero, loading cannot be assumed to be zero.
14 The a dvantag e of block d iagram rep resentation is that it is possible to evaluate the contribution of each component to the overall performance of the system.
a) True
b) False
Answer: - Option a
Explanation:The advantage of the block diagram is that it is possible to get the contribution of each
block to the overall performance of the system.
15 The o verall tr ansfer func tion from b lock diagra m reduction for cascad ed blocks is :
a) Sum of individual gain
b) Product of individual gain
c) Difference of individual gain
d) Division of individual gain
Answer: - Option b
16 Transfer funct ion of the s ystem is de fined as th e ratio of La place outp ut to Laplace input considering initial conditions________
a) 1
b) 2
c) 0
d) infinite
Answer: - Option c
Explanation: By definition transfer function is the ratio of the laplace output to the input but the initial
conditions mainly the stored energy is zero.
17 The m echanis m of contro l of body te mperature is non feed back syste m?
a) True
b) False
Answer: - Option b
Explanation: It is feedback system as the temperature of our body is regulated periodically and being
warm blooded we regulate our body temperature w.r.t. to the climate.
18 Benef its of fee dback:
a) Performance of system is greater.
b) Need for system much larger path gain and sy stem instab ility.
c) Controlled variable accurately follows the desired value
d) Affected by parameter variations
Answer: - Option d
Explanation: Closed loop system is the system with the feedback and this can be positive or negative
feedback and having feedback have less dependence on parameter variation.
19 Feedb ack alw ays increas es the gain ?
a) True
b) False
Answer: - Option b
Explanation: It cannot always increase gain it can also reduce the gain as gain of Open loop control
system is more as compared to it.
20 Feed back co ntrol system s are:
a) Insensitive to both forward and feedback path parameter changes
b) Less sensitive to feedback path parameter changes than to forward path parameter changes
c) Less sensitive to forward path parameter changes that to feedback path parameter changes
d) Equally sensitive to forward feedback path parameter changes
Answer: - Option c
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 change in H.
21 The c losed sy stem has h igher ____ ____ than o pen loop c ontrol syste m, this implies increased speed
of response.
a) Gain
b) Bandwidth
c) Frequency
d) Speed
Answer: - Option b
Explanation:As transient response of the system is improved by the use of feedback and it causes the
settling time to reduce and closed loop system has higher bandwidth than open loop systems and this
implies increase in speed of response.
22 Feedb ack can always red uce the eff ects of nois e and distu rbance on system performance?
a) True
b) False
Answer: - Option a
Explanation:Feedback has many advantages as it can reduces the effects of noise and disturbance
on system performance by increasing speed of response.
23 Multip le signa ls as input can be use d in which s ystems:
a) Feedback systems
b) Non feedback systems
c) Feedforward systems
d) None of the mentioned
Answer: - Option a
Explanation:As in feedback system output can be obtained for more than one input as output can be
generated for both the reference input and also for the disturbance input.
24 Feedb ack can cause a sy stem that i s originally stable to b ecome____ _______
a) Stable
b) Unstable
c) Conditionally stable
d) Either more stable or un stable
Answer: - Option d
Explanation:Feedback can either make a system stable if not stable previously or may be it can cause
instability as it reduces the gain of the system and hence the system can become stable if unstable or
vice versa.
25 Regenerative feedback im plies feed back with
a) Oscillations
b) Step input
c) Negative sign
d) Positive sign
Answer: - Option d
Explanation:Regenerative feedback that is the positive feedback implies feedback with Positive sign and for complementary root locus is for the regenerative feedback.
26 The o utput of a feedback control sys tem must b e a functio n ofa) Reference and output
b) Reference and input
c) Input and feedback signal
d) Output and feedback signal
Answer: - Option d
Explanation:The response of the control system is the output of the control system that depends upon
the transfer function of the system and feedback system and also upon the input of the system.
27 A con trol syst em with exc essive noi se, is likely to suffer fro m
a) Saturation in amplifying stages
b) Loss of gain
c) Vibrations
d) Oscillations
Answer: - Option a
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.
28 Zero i nitial con dition for a system me ans
a) Input reference signal is zero
b) Zero stored energy
c) Initial movement of movi ng parts
d) System is at rest and no energy is stored in an y of its com ponents
Answer: - Option d
Explanation:Zero initial condition means that the system is at rest and no energy is stored in any of its
component.
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: - Option c
Explanation:Transfer function of a system is that ratio of Laplace output to the Laplace input at zero
initial conditions and which is used to calculate the output for any given input.
30 The b and wid th, in a feed back ampl ifier.
a) Remains unaffected
b) Decreases by the same amount as the gain inc rease
c) Increases by the same amount as the gain decrease
d) Decreases by the same amount as the gain decrease
Answer: - Option c
Explanation:The bandwidth is defined as the difference in the higher frequency to the input frequency
and increase in the bandwidth leads to the noise and in a feedback amplifier increases by the same.
amount as the gain decreases.
31 On wh ich of th e following factors do es the sens itivity of a c losed loop system to gain changes and load
disturbances depend?
a) Frequency
b) Loop gain
c) Forward gain
d) All of the mentioned
Answer: - Option d
Explanation:Sensitivity is defined as the change in the output with respect to the change in the
parameter variations and the change in the input and load disturbances depends upon frequency loop
gain and forward gain.
32 The tr ansient response, w ith feedba ck system,
a) Rises slowly
b) Rises quickly
c) Decays slowly
d) Decays quickly
Answer: - Option d
Explanation:Transient response is the response that is between time t=0 and at any time and
behaviors depends upon the value of damping factor and maximum peak overshoot.
33 The s econd d erivative inp ut signals modify whi ch of the fo llowing?
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 oscillation s
Answer: - Option d
Explanation:The time constant is the time required to attain the final value of the steady state and the
value if less then the speed of response will be more and second derivative input signals modify
suppress the oscillations.
34 The e ffect of a dding feed back make s the syste m________ __
a) Linear
b) Non-linear
c) Time variant
d) Time invariant
Answer: - Option a
Explanation:Consider the single loop system with forward path transfer function as the square function
then the response generated is nonlinear if system is open loop but will be approximately linear if
closed loop.
35 The re lation b etween out put respon se and inpu t signal in c losed loop system is :
a) Exponential
b) Parabolic
c) Linear
d) Nonlinear
Answer: - Option c
Explanation:Due to the linearizing effect of the feedback the relation between output response and the
input signal in closed loop system is linear.
36 Asser tion (: P ractical sys tems must be closed lo op system .
Reason (R): This is due to the fact that closed loop systems are least affected by parameter variations,
stable, higher bandwidth, linear and more speed of response.
a) Both A and R are true and R is the correct explanation of A.
b) Both A and R are true but R is not the correct explanation of A.
c) A is true but R is false.
d) A is false but R is true.
Answer: - Option a
Explanation:Practically systems used must be linear to avoid error, ease of calibration and also to get
accurate results but the systems used are non-linear to avoid the error due to the linearity they are
approximated.
37 Regen erative feedback is also called as______ _________ __
a) Negative feedback
b) Positive feedback
c) No feedback
d) Negative and Positive Fe edback
Answer: - Option b
Explanation:As the name implies that is regenerates the oscillations hence by name it can be positive.
38 Which of the following are the characteristics of regenerative feedback:
a) Zero damping
b) Stable
c) Least sensitiv e to param eter variati ons
d) None of the mentioned
Answer: - Option a
Explanation:Output response is slow and sluggish and transient time is more due to the oscillations.
39 Which of the f ollowing ar e true:
a) Sensitivity of regenerative feedback is more than negative feedback but less than non-feedback
system
b) Sensitivity of regenerative feedback is more non-feedback system but less than negative feedback
system
c) Sensitivity of regenerative feedback is less than both
d) Sensitivity of regenerative feedback is more than both
Answer: - Option c
Explanation:Sensitivity of the positive feedback system is even more than non-feedback system and it
is more by a factor of 1/1-GH.
40. Loop gain provided by the regenerative feedback makes the closed loop transfer function insensitive to G(s).
a) TRUE
b) False
Answer: - Option a
Explanation:As if the positive feedback loop gain is nearly considered to be unity then transfer
function becomes insensitive to G(s).
41. 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 mentioned
Answer: a
Explanation: When the input to a system is independent of the output from the system, then the system
is called an open-loop or unmonitored system.
42.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 mentioned
Answer: a
Explanation: When output of a system is measured and is continuously compared with the required
value, then it is known as closed-loop or monitored system.
43. 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) none of the mentioned
Answer: a
Explanation: In closed loop control system, the output is measured and through a feedback transducer, it is sent to an error detector which detects any error in the output from the required value thus adjusting the input in a way to get the required output.
50. A signal flow graph is the graphical representation of the relationships between the variables of set
linear algebraic equations.
a) True
b) False
Answer: a
Explanation: By definition signal flow graphs are the graphical representation of the relationships
between the variables of set linear algebraic equations.
51. A node having only outgoing branches.
a) Input node
b) Output node
c) Incoming node
d) Outgoing node
Answer: a
Explanation: Nodes are the point by which the branches are outgoing or ingoing and this can be input or
output node and input node is the node having only outgoing branches.
52. Which of the following is not the feature of modern control system?
a) Quick respons
b) Accuracy
c) Correct power level
d) No oscillation
Answer: d
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.
53. The output of the feedback control system must be a function of:
a) Reference input
b) Reference output
c) Output and feedback signal
d) Input and feedback signal
Answer: d
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.
54. The principle of homogeneity and superposition are applied to:
a) Linear time invariant systems
b) Nonlinear time invariant systems
c) Linear time variant systems
d) Nonlinear time invariant systems Answer: c
Explanation: Superposition theorem states that for two signals additivity and homogeneity property must be satisfied and that is applicable for the LTI systems.
02 – Time domain stability analysis. Marks:-16
Content of Unit:-
2.1 Time Response : Transient & steady state response
2.2 Concepts of standard state inputs & it’s types
2.2.1 Step, Ramp, Parabolic & impulse concept.
2.3 Analysis of first & second order control systems, poles & zero concept.
2.3.1 Order of systems & its equations with numerical
2.3.2 First order system for unit step input , concept of time constant
2.3.3 second order system for unit step input , concept of time constant , concept ,definition
2.3.4 Time response specification – Tp , Ts & Tr details Time response specification – TD & Mp with
numerical
2.4 Steady state analysis for type 0, type 1 & type 2 system
2.4.1 Steady state errors & error constants with numerical
2.5 Details of stable & astable systems ,
2.5.1 concept of relative stability
2.6 Routh’s stability criteria & steps
1. A feedback control systems has the inherent capability that its parameter can be adjusted to alter both its transient and steady state responses.
a) True
b) False
Answer: a
Explanation: Feedback’s inherent capability is that its parameter can be adjusted to alter both transient
and steady state responses as together they are referred to as time responses.
2 Transient response analysis is done for__ _______ sy stems.
a) Unstable
b) Stable
c) Conditionally stable
d) Marginally stable
Answer: b
Explanation: In case the system happens to be unstable, we need not proceed with its transient
response analysis.
3. 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 mentioned
Answer: d
Explanation: System dynamic behavior for analysis and design is therefore judged and compared
under standard test signals.
4 Standard test signal s in control system are :
a) Impulse signal
b) Ramp signal
c) Unit step signal
d) All of the mentioned
Answer: d
Explanation: Standard test signals are impulse, ramp and unit step all of the above to test the dynamic
behavior of the control system.
5 The nature of transie nt respons e is reveal ed by ____ __________
a) Sine wave
b) Cos wave
c) Tan wave
d) Test signals
Answer: d
Explanation: The nature is dependent on system poles not on the dynamic inputs.
6 It is generally used to analyze the transien t response to one of the standard test signals.
a) True
b) False
Answer: a
Explanation: For analyzing transient response mainly step is used and also other signals mainly ramp
and parabolic are not used for this analysis but they are used for steady state analysis.
7 Step signal is the sig nal whose values is :
a) 1 for all values greater than zero
b) Indeterminate at zero
c) It is zero for time less than zero
d) All of the mentioned
Answer: d
Explanation: Step signal is the signal whose value varies from zero to level in zero time.
8 Ramp input :
a) Denotes constant velocity
b) Value increases linearly with time
c) It denotes constant velocity and varies linearly with time
d) It varies exponentially with time
Answer: c
Explanation: Ramp signal denotes constant velocity and also basic definition states that its value
increases linearly with time.
9 A perfect impulse h as one valu e at zero ti me instant but otherwise zero elsewhere.
a) True
b) False
Answer: b
Explanation: A perfect impulse signal has infinite value at zero but mathematically only a small pulse is taken with finite limits.
10 To find system’s res ponse by m eans of co nvolution in tegral ____________ of the system is used.
a) Sum
b) Difference
c) Exponential
d) Weighing
Answer: d
Explanation: Impulse response of a system is the inverse Laplace transfer function of its Laplace
function.
11 First order system is defined as :
a) Number of poles at origin
b) Order of the differential equation
c) Total number of poles of equation
d) Total number of poles and order of equation
Answer: d
Explanation: First order system is defined by total number of poles and also which is same as the order
of differential equation.
12. A unit step is applied at t=0 to a first order system without time delay. The response has the value of 1.264 units at t=10 mins, and 2 units at steady state. The transfer function of the system
is_____________
a) 3/(1+600s)
b) 2/(1+500s)
c) 5/(1+220s)
d) 2/(1+600s)
Answer: d
Explanation: a(t)= k[1-e^-t/T] K=2
0.632= 1-e^-10/T
T=600 sec
G(s)=2/(1+600s).
13. The transfer function of the system is G(s) =100/(s+1) (s+100). For a unit step input to the system the approximate settling time for 2% criterion is:
a) 100 sec
b) 4 sec
c) 1 sec
d) 0.01 sec
Answer: b
Explanation: G(s) =100/(s+1) (s+100)
Taking the dominant pole consideration,
S=-100 pole is not taken.
G(s)= 100/s+1
Now it is first order system, ts=4T=4 sec.
14. A system with transfer function 1/Ts+1, subjected to a step input takes to seconds to reach 50% of step height. The value of t is :
a) 6.9s
b) 10s
c) 14.4s
d) 20s
Answer: c
Explanation: The response of a first order system is:
A(t)=a[1-e^-t/T] ½= 1-e^-10/t
T= 14.43 sec.
15. Laplace transform o f unit impul se signal is :
a) A/s
b) A
c) 1
d) 1/s
Answer: c
Explanation: Laplace response of impulse signal is one which implies Laplace response is systems
response.
16. Time response during steady state the output velocity matches with the input velocity but lags behind
the input by T.
a) True
b) False
Answer: a
Explanation: In first order systems the time response during steady state the output velocity matches.
17 Which of the followin g transfer function wil l have the g reatest maximum overshoot?
a) 9/(s2+2s+9)
b) 16/(s2+2s+16)
c) 25/(s2+2s+25)
d) 36/(s2+2s+36)
Answer: d
Explanation: Comparing the characteristic equation with the standard equation the value of the
damping factor is calculated and the value for the option d is minimum hence the system will have the
maximum overshoot .
18 The damping ratio a nd peak ov ershoot are measures of:
a) Relative stability
b) Speed of response
c) Steady state error
d) Absolute stability
Answer: b
Explanation: Speed of response is the speed at which the response takes the final value and this is determined by damping factor which reduces the oscillations and peak overshoot as the peak is less then the speed of response will be more.
20. A system has a complex conjugate root pair of multiplicity two or more in its characteristic equation.The impulse response of the system will be:
a) A sinusoidal oscillation which decays exponentially; the system is therefore stable
b) A sinusoidal oscillation with a time multiplier ; the system is therefore unstable
c) A sinusoidal oscillation which rises exponentially ; the system is therefore unstable
d) A dc term harmonic oscillation the system therefore becomes limiting stable
Answer: c
Explanation: Poles are the roots of the denominator of the transfer function and on imaginary axis
makes the system stable but multiple poles makes the system unstable.
21. What will be the nature of time response if the roots of the characteristic equation are located on the splane
imaginary axis?
a) Oscillations
b) Damped oscillations
c) No oscillations
d) Under damped oscilaations
Answer: c
Explanation: complex conjugate (non-multiple): oscillatory (sustained oscillations)
Complex conjugate (multiple): unstable (growing oscillations).
22 Which one of the fol lowing is th e most like ly reason fo r large overshoot in a control system?
a) High gain in a system
b) Presence of dead time delay in a system
c) High positive correcting torque
d) High retarding torque
Answer: c
Explanation: Large overshoot refers to the maximum peak in the response of the closed loop system
and this is mainly due to the high positive correcting torque.
23 In a second order fe edback con trol system natural fre quency and damping
a) Can be designed by changing the gain of the individual system
b) Cannot be designed by changing the gain of the individual system
c) Are independent on the type of input excitation
d) None of the mentioned
Answer: a
Explanation: Natural frequency and damping can be designed by changing the gain of the individual
system.
24. The transfer function of a system is G(s) = 100/(s+1) (s+100). For a unit step input to the system the approximate settling time for 2% criterion is:
a) 100 sec
b) 4 sec
c) 1 sec
d) 0.01 sec
Answer: b
Explanation: Comparing the equation with the characteristic equation and then finding the value of G
and w and calculating the value of settling time as 4 sec from 4/Gw.
25
Rise time, Peak time, maximum peak overshoot, settling time, and steady state error are mutually
dependent.
a) True
b) False
Answer: a
Explanation: Rise time, peak time, settling time and maximum peak overshoot are the prime factors of
the time domain analysis and they must be specified in a consistent manner but they are mutually
dependent.
26 Control system are n ormally de signed to b e:
a) Overdamped
b) Under damped
c) Un damped
d) Critically damped
Answer: b
Explanation: Practically there are some non-linearity present in the system as friction but in
mathematical model these are considered by considering high gain and lower damping.
27 Stability of a system implies th at :
a) Small changes in the system input does not result in large change in system output
b) Small changes in the system parameters does not result in large change in system output
c) Small changes in the initial conditions does not result in large change in system output
d) All of the above mentioned
Answer: d
Explanation: Stability of the system implies that small changes in the system input, initial conditions,
and system parameters does not result in large change in system output.
28 A linear time invaria nt system is stable if :
a) System in excited by the bounded input, the output is also bounded
b) In the absence of input output tends zero
c) Both a and b
d) System in excited by the bounded input, the output is not bounded
Answer: c
Explanation: A system is stable only if it is BIBO stable and asymptotic stable.
29 Asymptotic stability is concerne d with:
a) A system under influence of input
b) A system not under influence of input
c) A system under influence of output
d) A system not under influence of output
Answer: b
Explanation: Asymptotic stability concerns a free system relative to its transient behavior.
30 Bounded input and B ounded ou tput stabili ty notion co ncerns with :
a) A system under influence of input
b) A system not under influence of input
c) A system under influence of output
d) A system not under influence of output
Answer: a
Explanation: BIBO stability concerns with the system that has input present.
31 If a system is given unbounded input then the system is:
a) Stable
b) Unstable
c) Not defined
d) Linear
Answer: c
Explanation: If the system is given with the unbounded input then nothing can be clarified for the
stability of the system.
32 Linear mathematica l model ap plies to :
a) Linear systems
b) Stable systems
c) Unstable systems
d) Non-linear systems
Answer: b
Explanation: As the output exceeds certain magnitude then the linear mathematical model no longer
applies.
33 For non-linear syste ms stability cannot be determine d due to:
a) Possible existence of multiple equilibrium states
b) No correspondence between bounded input and bounded output stability and asymptotic stability
c) Output may be bounded for the particular bounded input but may not be bounded for the bounded
34 If the impulse response in abso lutely integ rable then the system is :
a) Absolutely stable
b) Unstable
c) Linear
d) Stable
Answer: a
Explanation: The impulse response must be absolutely integrable for the system to absolutely stable.
35 The roots of the tran sfer functio n do not ha ve any effe ct on the stability of the system.
a) True
b) False
Answer: b
Explanation: The roots of transfer function also determine the stability of system as they may be real,
complex and may have multiplicity of various order.
36 Roots with higher m ultiplicity on the imagin ary axis m akes the system :
a) Absolutely stable
b) Unstable
c) Linear
d) Stable
Answer: b
Explanation: Repetitive roots on the imaginary axis makes the system unstable.
37 Roots on the imagin ary axis ma kes the sy stem :
a) Stable
b) Unstable
c) Marginally stable
d) Linear
Answer: c
Explanation: Roots on the imaginary axis makes the system marginally stable.
38 If the roots of the ha ve negative real parts then the re sponse is ____________
a) Stable
b) Unstable
c) Marginally stable
d) Bounded
Answer: d
Explanation: If the roots of the have negative real parts then the response is bounded and eventually decreases to zero.
44. Standard test signals in control system are:
a) Impulse signal
b) Ramp signal
c) Unit step signal
d) All of the mentioned
Answer: d
Explanation: Standard test signals are impulse, ramp and unit step all of the above to test the dynamic
behavior of the control system.
45. The nature of transient response is revealed by ______________
a) Sine wave
b) Cos wave
c) Tan wave
d) Test signals
Answer: d.
Explanation: The nature is dependent on system poles not on the dynamic inputs.
46. .It is generally used to analyze the transient response to one of the standard test signals.
a) True
b) False
Answer: a
Explanation: For analyzing transient response mainly step is used and also other signals mainly ramp
and parabolic are not used for this analysis but they are used for steady state analysis.
47. Step signal is the signal whose values is :
a) 1 for all values greater than zero
b) Indeterminate at zero
c) It is zero for time less than zero
d) All of the mentioned
Answer: d
Explanation: Step signal is the signal whose value varies from zero to level in zero time.
48. Ramp input :
a) Denotes constant velocity
b) Value increases linearly with time
c) It denotes constant velocity and varies linearly with time
d) It varies exponentially with time\
Answer: c
03 – Process controller. Marks:-16
Content of Unit:-
3.1 Block diagram & functions of process control systems
3.2 control action
3.1.1 Discontinuous mode of on - off controllers systems.
3.1.2 On -off controller equation & neutral zone concept. Proportional controller in continuous mode
3.3 composite controllers
3.3.1 Integral & derivative controller with equations &Bit’s response
3.3.2 PI composite controllers with equations PD ,PID controllers with output equations
1 The transfer function of PID controller is:
a) KP + KI/s + KDs
b) s.KP + KI/s + KDs
c) KP + s.KI + KD/s
d) s.KP + KI/s + KD/s
Correct answer: 1. KP + KI/s + KDs
Explanation:
The transfer function of a proportional controller is KP
While transfer function of the integral controller is KI/s
While transfer function of derivative controller is KDs
Since a PID controller (Proportional, Integral, Derivative controller)
is a combination of all the three, the transfer function of PID
controller is KP + KI/s + KDs
2 Which controller cannnot be used for constant error:
a) P controller
b) I controller
c) D controller
d) PI controller
Correct answer: option c
Explanation: The derivative controller produces a control action based on the rate of change of error signal and it does not produce corrective measures for any constant error.
3 Which control action produces a c onstant steady state error.
a) P controller
b) I controller
c) D controller
d) PI controller
Correct answer: option a
Explanation: The disadvantage in proportional controller is that it
produces a constant steady state error.
4. Following is the is the effect of PD controller on system
performance
a) Increses gain
b) increases damping ratio
c) Decreases gain
d) Decreases daming ratio
Correct answer: b
Explanation: The effect of PD controller is to increase the damping ratio of the system and so the peak
overshoot is reduced.
5. A proportional plus derivative cont roller:
a) 1. has high sensitivity.
b) 2. increases the stability of the system.
c) 3. improves steady-state accuracy.
Which of the above statements are correct?
1, 2, and 3
1 and 2 only
1 and 3 only
Answer: Option b
Explanation: Proportional + Derivate:
The additive combination of proportional & Derivative control is known as P-D control. The overall transfer function for a PD controller is given by:
The frequency of noise is very high. So this high pass filter will allow noise into the system which results in noise amplification. Effects of Proportional Derivative (PD) controllers: Decreases the type of the system by one Reduces the rise time and settling time It has high sensitivity. Rise time and settling time decreases and Bandwidth increases The speed of response is increased i.e. the transient response is improved Improves gain margin, phase margin, and resonant peak Increases the input noise Improves the stability
6 Slow response of an over-damped system can be made faster with th e help of __ ____ contr oller.
a) PD
b) P
c) PI
d) Remote
Answer: Option b
7 A condition where integral control drives the output of a controller into saturation is called __ ____
a) Wind - Up
b) Noise
c) Repeat
d) Offset
Answer: Option a
8 The electric switch to control any electrical equipment will act as a:
a) PD controller
b) Proportional controller
c) PID controller
d) ON/OFF controller
Answer: Option d
9. A Control system with PD controller is shown. If velocity error
constant is K = 1000 and the damping ratio is 0.5 then the values
of K and K Should be:
a) Kp = 100, KD = 0.09
b) KP = 100, KD = 0.9
c) KP = 10, KD = 0.09
d) KP = 10, KD = 0.9
Answer: Option b
10
In a closed-loop process control system with a PID controller,
_________ response depends only on the difference between set
point and the process variable.
a) proportional
b) integral
c) differential
d) All of these
Answer: Option d
11 What effect does the proportional parameter of control response
have on the rise time in a closed-loop control system?
a) It decreases
b) It eliminates
c) No changes
d) It increases
Answer: Option a
12 The controller which is highly sens itive to noise is
a) PI
b) PD
c) Both PI and PD
d) Neither PI nor PD
Answer: Option b
13 The effect of integral controller on the steady state error (e ) and on th e relative s tability (R ) of the syste m are
a) Both are increased
b) ess is increased but Rs is reduced
c) ess is reduced but Rs is increased
d) Both are reduced
Answer: Option d
Explanation:
Integral control is based on the principle that the controller’s output should be proportional to both the magnitude and duration of the error. The controller’s output will continue to change its value until the error is zero. This property enables integral action to eliminate offset error automatically (∴ It is sometimes called as automatic reset controller) Also, a smaller amplitude causes a slower rate of change of the output.
14 A proportional integral (PI) control ler results in which of the following ?
a) Improves the transient response without affecting steady state response
b) Improves the steady state response without affecting transient response
c) Improves both transient response and steady state response
d) Improves the steady state response while marginally affecting transient response, for well designed
control parameters
Answer: Option d
15 Which of these statements is corre ct about proportional plus derivative controller?
a) It decreases the stability of the system
b) It has high sensitivity
c) It improves the steady-state accuracy
d) The derivative constant is expressed in units of hours
Answer: Option b
16 Which of the following is a correct statement
a) PI controllers improves steady state response
b) PD controllers improves transient response
c) Both (a) & (b)
d) None of these
Answer: Option c
1 9. The input of a controller is
a) Sensed signal
b) Error signal
c) Desired variable value
d) Signal of fixed amplitude not dependent on desired variable value
Answer: b
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.
20. PD controller is used to compensate system. Compared to the uncompensated system, the
compensated system has:
a) A higher type number
b) Reduced damping
c) Higher noise amplification
d) Large transient overshoot
Answer: c
Explanation: Proportional Derivative controller is used to increase the bandwidth and also increases the
signal to noise ratio by reducing the noise and increasing the signal.
21. P+D controller:
a) Introduces offset
b) Increases bandwidth
c) Increases margin of stability
d) Reduces velocity constant
Answer: c
Explanation: Proportional Derivative controller is the controller increases margin of stability and also
used to increase he bandwidth and also increases the signal to noise ratio.
22. Proportional controller:
a) Introduces offset
b) Increases bandwidth
c) Increases margin of stability
d) Reduces velocity constant
Answer: a
Explanation: Proportional controller is the controller that is block used to control the gain of the control
system and introduces offset error and there is no effect on the damping factor.
23. The transfer function of a lead controller is 1+20s/1+5s. The high frequency magnitude of the lead
controller to dB is ___________
a) 1
b) 2
c) 3
d) 4
Answer: d
Explanation: G(s) = Tp (1+Tds)/s^2
It is type-2 function.
The type-2 function has a finite steady state error for unit-parabolic input.
24. Controllers play the following role in control system:
a) They amplify the signals going to the actuator
b) They act on the error signal coming out of the summing junction and output a suitable to the actuator
c) They try to reduce steady state error optimizes overshoot.
d) All of the mentioned
Answer: a
Explanation: Controller amplify the signals going to the actuator and they are of many types as
proportional, integral, derivative some combinational controller as combination of two controllers and
combination of all the controllers.
25. Consider the following statements:
1. Integral controller improves steady state response
2. By use of proportional controller, maximum peak overshoot decreases
3. Type and order of system reduces by one for derivative controller
4. Integral controller makes the system less stable in transient state due to oscillations
Select the correct answer using the codes given below:
a) 1,3 and 4
b) 1,2 and 3
c) 2.3 and 4
d) 1,2 and 4
Answer: a
Explanation: Integral controller improves steady state response and derivative controller improves the
transient response, type and order of system reduces by one for derivative controller.
26. Rate mode controller is also known as ______________ controller mode.
a) Anticpatory
b) Delay
c) Integral
d) Derivative
Answer: a
Explanation: Anticipatory controller mode is also known as the rate mode controller that is used to
anticipate the future value with the use of the state.
27. The controller required to handle fast process load changes is:
a. PD controller
b. PI Controller
c. PID Controller
d. None of the above
Answer: (a) PD controller
Explanation: The Proportional Derivative controller is preferred to handle fast process load
changes.
28. What is the relationship between the steady-state error, gain and the tendency of oscillations
when the controller is supposed to be under the proportional action?
a. Steady-state error increases with an increase in gain and oscillation tendency
b. Steady-state error decreases with the decrease in gain and oscillation tendency
c. Steady-state error decreases with an increase in gain and oscillation tendency
d. Steady-state error increases with the decrease in gain and oscillation tendency
ANSWER: c. Steady-state error decreases with an increase in gain and oscillation tendency
04 – Fundamentals of PLC. Marks:-16
Content of Unit :-
4.1 PLC block diagram, classification, benefits & it’s need.
4.2 Description of PLC
4.2.1 Scanning cycle, speed of execution
4.2.2 Power supply of PLC & its function of each block.
4.2.3 Different memories, their functions & organizations.
4.2.4 PLC input & output modules with their functions
4.3 PLC installation
4.3.1 PLC installation & review of PLC fundamentals
1 The programmable logic controllers are used in __________
a) Manufacturing
b) Automation
c) Both a and b
d) None of the above
Answer: option c
Explanation:
The PLC is extensively used in manufacturing and automation. Its purpose is to monitor crucial process parameters and to adjust process operation accordingly
2 What are the components that make the program mable logic controller work?
a) Input and output module
b) CPUPower supplyAll of the above
c) Power supply
d) All of the above
Answer: option d
Explanation: The input module, output module, CPU, and power supply are the components that make the programmable logic controller work
3 In fixed programmable logic controller _______
a) Input is fixed
b) Output is fixed
c) Both a and b
d) None of the above
Answer: option c
Explanation: In fixed programmable logic controller both input and output modules are fixed whereas in modular PLC the input and output modules are not fixed
4 The PLC’s can be programmed in _______
a) Ladder logic,
b) structured textInstruction list,
c) Functional block diagramSequential function chartA
d) All of the above
Answer: option d
Explanation:
The programmable logic controllers can be programmed in ladder logic, structured text, instruction list, functional block diagram, and sequential function chart
5 In modular programmable logic controller _____ __
a) Input is fixed
b) Output is fixed
c) Both a and b
d) None of the above
Answer: option c
Explanation:
In modular PLC the input and output modules are expandable whereas in fixed programmable logic
controller both input and output modules are fixed
6 What are the types of programmable logic contro llers?
a) Fixed,
b) uniform PLCModular,
c) Fixed and Modular PLC
d) None of the above
Answer: option b
Explanation:
The PLC’s are classified into two types they are: fixed programmable logic controller and modular
programmable logic controller
7 The components that make PLC works can be di vided into ____________ core areas
a) One
b) Two
c) Three
d) Four
Answer: option c
Explanation:
The components that make PLC works can be divided into three core areas they are input/output,
CPU, rack, and power supply
8 How many operation steps does the programmable logic controller have?
a) One
b) Two
c) Three
d) Four
Answer: option c
Explanation: The programmable logic controller operation is of three steps they are input scan, output scan, and program scan
9 In PLC operation ___________ checks the status at the input side
a) Input scan
b) Output scan
c) Program scan
d) None of the above
Answer: option a
Explanation:
The input scan checks the status at the input side in the programmable logic controller operation
10 In PLC operation ___________ retrieves the data into an output module
a) Input scan
b) Output scan
c) Program scan
d) None of the above
Answer: option b
Explanation:
In PLC operation output scan retrieves the data into an output module, so that all the outputs are
updated
11 Before PLC’s was created many industries used _________
a) Capacitors
b) Relays
c) Resistors
d) None of the above
12. The hundreds and thousands of relays are used in industries when programmable logic controllers are not developed
CCTV cameras is an example for ________ automation
a) Building automation
b) Office automation
c) Scientific automation
d) Industrial automation
Answer: option b
Explanation:
The CCTV cameras come under office automation
13 The control logic in a programmable logic contro ller can be programmed by
a) FBD
b) ladder logic
c) Sequential logicStructured text
d) All of the above
Answer: option d
Explanation:
The control logic in a programmable logic controller can be programmed using different programming
languages some of them are FBD, ladder logic, sequential logic, & structured text
14. The programmable logic controllers are classified into _________ according to physical size in
modular type PLC
a) Mini PLC,
b) Micro PLCMicro PLC
c) None of the above
d) Nano PLC, Mini PLC, Macro PLC
Answer: option d
Explanation:
The programmable logic controllers are classified into three types according to physical size in modular type PLC they are mini, micro, and nano PLC
15 The advantages of PLC are ______
a) Easy maintenance
b) Reliability is high
c) Small in size
d) All of the above
Answer: option d
Explanation:
The programmable logic controllers are small in size, reliability is very high, and the maintenance of
these controllers are very easy
16 The CPU has ______
a) Memory system
b) Processor
c) Power supply
d) All of the above
Answer: option d
Explanation:
The CPU is a control portion of the programmable logic controller that consists of a memory system,
processor, and power supply
17 _________ are the components that are required to change or create a program
a) PLC
b) programming device
c) Programming software
d) All of the above
Answer: option d
Explanation:
The components that are required to change or create a program are PLC, programming device and software, and connector cable
18 The sequences are classified into _________
a) One
b) Two
c) Three
d) Four
Answer: option c
Explanation:
The sequences are classified into three types they are single sequence, complicated single sequence,
and multiple sequences
19 The PLC internally operates, stores, and calculat es the value in _____
a) Binary format
b) Decimal format
c) Octal format
d) None of the above
Answer: option a
Explanation:
The PLC stores operate and calculate the value in a binary number format
20. Which one is the correct sequence for PLC oper ation?
a) Self-test, input scan, logic scan, output scan
b) Self-test, logic scan, output scan, input scan
c) elf-test, input scan, output scan, logic scan
d) None of the above
Answer: option a
Explanation:
The correct sequence for PLC operation is self-test, input scan, logic scan, output sca
21 The electromagnetic relays are constructed with _______
a) Electrical components
b) Mechanical components
c) Electromechanical components
d) None of the above
Answer: option c
Explanation:
The electromagnetic relays are constructed with electromechanical components, and an operating coil
and mechanical contacts
22 The DC and AC relays works on __________ prin ciple
a) Motors
b) Electromagnetic induction
c) Electromechanical components
d) None of the above
Answer: option b
Explanation:
The DC and AC relays both works on the electromagnetic induction principle but the construction is
somewhat differentiate
23 The ladder logic in PLC consists of _________
a) Logic gates
b) Functional blocks
c) Relay contacts
d) Relays
Answer: option d
Explanation:
The ladder logic in PLC consists of relays
24 __________ is an example for office automation ?
a) Rocket launching
b) Street solar lightening
c) Printers
d) CCTV cameras
Answer: option d
Explanation:
The printers and CCTV cameras are an example for office automation
25 The relays operates on __________
a) Low power
b) Control circuits of very high power
c) Both a and b
d) None of the above
Answer: option c
Explanation:
The relays operate on low power and can be used to control a circuit
26 What are the elements of ladder logic?
a) Normally open (contact)
b) Normally Close (contact)
c) Both a and b
d) None of the above
Answer: option c
Explanation:
The normally open and normally close are the two elements of the ladder logic
27 What is the standard form of FBD?
a) Functional Block DiagramFirst Block DiagramFunctional Block DivisionNone of the above
b) First Block Diagram
c) Functional Block Division
d) None of the above
Answer: option a
Explanation:
The standard form of FBD is Functional Block Diagram
28 What are the components that are used to make relay __________
a) Electromagnet
b) Spring
c) Armature
d) All of the above
Answer: option d
Explanation:
The electromagnet, spring, and armature are the components that are used to make relays
29 Why programmable logic controllers are require d?
a) It reduces the efforts of human begins
b) To get the maximum efficiency
c) To reduce the complex circuitry of entire system
d) All of the above
Answer: option d
Explanation:
The programmable logic controllers are required to reduce the human begins efforts, to get the
maximum efficiency, and to reduce the complex circuitry of the entire system
30 ___________ is an example for input modules in programmable logic controller
a) Switches
b) Pushbuttons
c) Lamps
d) Both a and b
Answer: option d
Explanation:
The switches and pushbuttons are examples of input modules in the programmable logic controller
31 __________ is an example for output modules in the programmable logic controller
a) Switches
b) Alarms
c) Lamps
d) Both b and c
Answer: option d
32 How many inputs does a unitary programmable l ogic controller have?
a) 10, 15
b) 15, 20
c) 20-40
d) 20, 12
Answer: option d
Explanation:
The unitary programmable logic controller has 20 inputs and 12 outputs
33 How many input and output pins do a small prog rammable logic controller have?
a) 10
b) 30
c) 50
d) 128
Answer: option d
Explanation:
The small programmable logic controller has a total of 128 input and output pins
34 _________ is connected to the PLC input
a) Indicating lamp
b) Field sensors
c) Both a and b
d) None of the above
Answer: option b
Explanation:
The field sensors are one type of input device that is connected to the PLC input
35 The programmable logic controller works on ___ _______
a) Parallel mechanism
b) Sequential mechanism
c) Both a and b
d) None of the above
Answer: option b
Explanation:
The programmable logic controller works on the sequential mechanism
36 How many input and output pins do a nano prog rammable logic controller have?
a) 16
b) 30
c) 50
d) 128
Answer: option a
37 How many input and output pins do a micro prog rammable logic controller have?
a) 32
b) 30
c) 50
d) 128
Answer: option a
Explanation:
The micro programmable logic controller has a total of 32 input and output pins
38 ________ can be connected to the analogue outp ut of the programmable logic controller
a) Control valve
b) Level transmitter
c) Flow transmitter
d) None of the above
Answer: option a
Explanation:
The control valve can be connected to the analog output of the programmable logic controller
39 ________ provides the voltage to PLC primary components
a) Control valve
b) Level transmitter
c) Flow transmitter
d) Power supply
Answer: option d
Explanation:
The power supply provides the voltage needed to run the PLC primary components
40 Which type of memory is used in PLC?
a) Random Access Memory
b) Read Only Memory
c) Both a and b
d) None of the above
Answer: option c
Explanation:
The type of memories used in PLCs are read-only memory and random access memory to stores the information, program, and data in a PLC
05 – PLC Hardware and Programming Marks:-16
Content of Unit :-
5.1 Block diagram & specification of AC input module
5.2 Block diagram & specification of DC input module
5.2.1 Sinking & Sourcing concept in DC module
5.3 Block diagram & specification of Analog input output module
5.3.1 Analog input PLC module diagram and specification
5.3.2 Analog output PLC module specification
5.4 I/O addressing of PLC
5.4.1 Addressing of data files & different types of addressing
5.5 PLC instruction set
5.5.1 Relay instruction, timer instruction
5.5.2 PLC instruction set - counter instruction, data movement instruction
5.5.3 PLC instruction set -logical & comparison instruction
5.6 PLC programming - Ladder programming language
1. Which one is the correct sequence for PLC operation?
a) Self-test, input scan, logic scan, output scan
b) Self-test, logic scan, output scan, input scan
c) Self-test, input scan, output scan, logic scan
d) None of the above
Answer: a
Explanation: The correct sequence for PLC operation is self-test, input scan, logic scan, output scan
2. electromagnetic relays are constructed with
a) Electrical components
b) Mechanical components
c) Electromechanical components
d) None of the above
Answer: c
Explanation: The electromagnetic relays are constructed with electromechanical components, and an operating coil and mechanical contacts
3. The DC and AC relays works on principle
a. Motors
b. Electromagnetic induction
c. Electromechanical components
d. None of the above
Answer: b
Explanation: The DC and AC relays both works on the electromagnetic induction principle but the
construction is somewhat differentiate
4. The attraction type electromagnetic relays works with
a. AC supply
b. DC supply
c. Both ac and dc supply
d. None of the above
Answer: c
Explanation: The attraction type electromagnetic relays works on both AC and DC supply that attract a metal bar or piece of metal
5. In PLC the user can write the programs with the help of
a. Optical isolation
b. Sensing devices
c. Programming devices
d. N
one of the
above
Answer: c
Explanation: In PLC the user can write the programs with the help of programming devices, the
programming devices is an interface between PLC and the user
6. The system that is used to direct, regulate or command itself
a) Open-loop
b) Close-loop
c) Both A and D
d) Con
trol
system
Answer: d
Explanation: The control system is used to direct, regulate or command itself
7). In which control system feedback is available?
a) Open-loop
b) Close-loop
c) Both A and D
d) None of
the above
Answer: b
Explanation: The feedback is available in a closed-loop control system
. 8). Relays is a device
a) Electrical devices
b) Electromechanical devices
c) Mechanical devices
d) None of
the above
Answer: b
Explanation: The relays are electromechanical devices
. 9). Which one is the PLC programming language?
a) HMI
b) MMI
c) FBD
d) None of
the above
Answer: c
Explanation: The functional block diagram is one type of programmable logic controller programming language.
10). The standard form of PLC is
a) Programmable Logic Controller
b) Programmable Load Controller
c) Pressure Load Controller
d) None of
the above
Answer: a
Explanation: The standard form of PLC is Programmable Logic Controller, it is one type of logic controller
34). The programmable logic controller works on
a) Parallel mechanism
b) Sequential mechanism
c) Both a and b
d) None of
the above
Answer: b
Explanation: The programmable logic controller works on the sequential mechanism.
35). How many input and output pins do a nano programmable logic controller have?
a) 16
b) 30
c) 50
d) 128
Answer: a
Explanation: The nano programmable logic controller has a total of 16 input and output pins
36). How many input and output pins do a micro programmable logic controller have?
a) 32
b) 30
c) 50
d) 128
Answer: a
Explanation: The micro programmable logic controller has a total of 32 input and output pins
37). can be connected to the analogue output of the programmable logic controller
a) Control valve
b) Level transmitter
c) Flow transmitter
d) None of
the above
Answer: a
Explanation: The control valve can be connected to the analog output of the programmable logic controller
38). provides the voltage to PLC primary components
a) Control valve
b) Level transmitter
c) Flow transmitter
d) Powersupply
Answer: d
Explanation: The power supply provides the voltage needed to run the PLC primary components
39). Which type of memory is used in PLC?
a) Random Access Memory
b) Read Only Memory
c) Both a and b
d) None of the above
Answer: c
Explanation: The type of memories used in PLCs are read-only memory and random access memory to stores the information, program, and data in a PLC
40). The CPU consists of
a) Arithmetic Logic Unit
b) Internal memory of CPU
c) Internal timers, counters, flags
d) All
of the
above
Answer:D