Here are 1000 MCQs on Control System (Chapterwise).
1. What is Control System?
a) Control system is a system in which the output is controlled by varying the input
b) Control system is a device that will not manage or regulate the behaviour of other devices using control loops
c) Control system is a feedback system that can be both positive and negative
d) Control System is a system in which the input is controlled by varying the output
View Answer
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) Correct power level
b) No oscillation
c) Quick response
d) Accuracy
View Answer
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. What is the characteristic of a good control system?
a) Insensitive to the parameter variation but sensitive to the input commands
b) Neither sensitive to parameter variations nor sensitive to input commands
c) Insensitive to the input command
d) Sensitive to parameter variation
View Answer
Explanation: In a good control system, the output is sensitive to input variations but insensitive to parameter variations.
4. Which of the following element is not used in an automatic control system?
a) Final control element
b) Sensor
c) Oscillator
d) Error detector
View Answer
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.
5. A control system working under unknown random actions is called ____________
a) Adaptive control system
b) Stochastic control system
c) Computer control system
d) Digital data system
View Answer
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.
6. Which of the following is an open loop control system?
a) Ward Leonard control
b) Metadyne
c) Stroboscope
d) Field controlled D.C. motor
View Answer
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.
7. 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 mentioned
View Answer
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.
8. What should be the nature of bandwidth for a good control system?
a) Small
b) Medium
c) Large
d) All of the mentioned
View Answer
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.
9. The output of the feedback control system must be a function of ____________
a) Output and feedback signal
b) Input and feedback signal
c) Reference input
d) Reference output
View Answer
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.
10. 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
View Answer
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.
11. In a stable control system backlash can cause which of the following?
a) Overdamping
b) Low-level oscillations
c) Underdamping
d) Poor stability at reduced values of open loop gain
View Answer
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.
12. In a control system the output of the controller is given to
a) Amplifier
b) Sensor
c) Final control element
d) Comparator
View Answer
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.
13. A Control System with excessive noise, is likely to suffer from which of the following?
a) Oscillations
b) Saturation in amplifying stages
c) Loss of gain
d) Vibrations
View Answer
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.
14. In a temperature control system, what conversion in signal takes place?
a) Error to Digital
b) Error to Analog
c) Digital to Analog
d) Analog to Digital
View Answer
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.
15. Which of the following control systems have unpredictable & non-repeatable?
a) Stochastic control systems
b) Deterministic control systems
c) Static control systems
d) Dynamic control systems
View Answer
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.
16. In pneumatic control systems the control valve used as the final control element converts
a) Position change to pressure signal
b) Electric signal to pressure signal
c) Pressure signal to electric signal
d) Pressure signal to position change
View Answer
Explanation: In pneumatic control systems the control valve is used as the final control element to convert pressure signal to position change.
17. 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, iii and iv only
b) i, ii and iii only
c) i, iii and iv only
d) i, ii and iv only
View Answer
Explanation: Negative feedback increases stability but not positive positive feedback reduces the stability and for this reason negative feedback systems are used.
18. In closed loop control system, what is the sensitivity of the gain of the overall system, M to the variation in G?
a) G/1GH
b) 1/1+GH
c) G/1+G
d) 1/1+G
View Answer
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.
19. 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) Constant velocity and acceleration
b) Sudden shock
c) Sudden change
d) All of the mentioned
View Answer
Explanation: System dynamic behavior for analysis and design is therefore judged and compared under standard test signals.
20. 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°
View Answer
Explanation: P-Z = 3
Angle of asymptote = (2q+1)180°/P-Z
Hence the angles are 60°, 180°, and 300°.
21. Feedback control system is basically ______________
a) Band pass filter
b) Band stop filter
c) High pass filter
d) Low pass filter
View Answer
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.
22. Which of the following is not a feature of a good control system?
a) Slow response
b) Sufficient power handling capacity
c) Good stability
d) Good accuracy
View Answer
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.
23. A control system is generally met with the time response specifications:
a) Damping factor
b) Setting time
c) Steady state accuracy
d) All of the mentioned
View Answer
Explanation: Steady state error, damping factor and settling times are the specifications are needed to control the system’s stability and speed of response.
24. 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)
b) 4 and (-4,0)
c) -3 and (-12,0)
d) 3 and (-12,0)
View Answer
Explanation: 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.
25. With negative feedback in a closed loop control system, the system sensitivity to parameter variation:
a) Becomes infinite
b) Becomes zero
c) Decreases
d) Increases
View Answer
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).
26. 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)
b) 10(s+2)/(s+10)
c) 10(s+2)/(s+10)
d) 10(s-1)/(s+2)
View Answer
Explanation: 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.
27. Controllers play which of the following role in the control system?
a) They act on the error signal coming out of the summing junction and output a suitable to the actuator
b) They try to reduce steady state error optimizes overshoot
c) They amplify the signals going to the actuator
d) All of the mentioned
View Answer
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.
28. In control system excessive bandwidth is not employed because
a) It leads to slower time response
b) Noise is proportional to bandwidth
c) Noise is proportional to the square of the bandwidth
d) It leads to low relative stability
View Answer
Explanation: In closed loop system the bandwidth of the system is more as compared to the open loop system and this is so required as higher the bandwidth means lower the selectivity and hence higher the noise.
29. What is the relation between output response and input signal in closed loop system?
a) Nonlinear
b) Linear
c) Exponential
d) Parabolic
View Answer
Explanation: Due to the linearizing effect of the feedback the relation between output response and the input signal in closed loop system is linear.
30. Which of the following is the input of a controller?
a) Signal of fixed amplitude not dependent on desired variable value
b) Desired variable value
c) Sensed signal
d) Error signal
View Answer
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.
31. Which of the following are the not characteristics of the closed loop systems?
a) It does not have the ability to control the system transient response
b) It does not involve I/O measurements
c) It reduces the sensitivity of plant-parameter variations
d) It does not compensate for disturbance
View Answer
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.
32. 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
b) 0.5/(s+1)(s+2)
c) 1/(s+2)(s+1)
d) 1/(s+3)
View Answer
Explanation: 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).
33. Effect of feedback on sensitivity is minimum in:
a) Closed loop control system
b) Open and closed loop control systems
c) Open loop control system
d) None of the mentioned
View Answer
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).
34. 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) 0.15
b) 0.20
c) 0.25
d) 0.10
View Answer
Explanation: 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.
35. Sampling is necessary ____________
a) Non automated control system
b) Automated control system
c) In complex control system
d) Where high accuracy is required
View Answer
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.
36. Which of the motions in actuators are preferred?
a) Rotary
b) Stationary
c) Non-Stationary
d) Translator
View Answer
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.
Chapterwise Multiple Choice Questions on Control System
- Mathematical Models of Physical Systems
- Feedback Characteristics of Control Systems
- Control System and Components
- Time Response Analysis, Design Specifications and Performance Indices
- Stability and Algebraic Criteria
- Root Locus Technique
- Frequency Response Analysis
- Stability in Frequency Domain
- Control System Design
- Digital Control Systems
- State Variable Analysis and Design
- Liapunov’s Stability Analysis
- Optimal Control Systems
- Nonlinear Systems
- Advances in Control System
- Error Analysis
1. Control System MCQ on Mathematical Models of Physical Systems
The section contains Control System multiple choice questions and answers on transfer functions, block diagram algebra, signal flow graphs and equations of physical systems.
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2. MCQ on Feedback Characteristics of Control Systems
The section contains Control System questions and answers on linearizing effect and regenerative feedback, effects of disturbance signal by using feedback, feedback and non-feedback systems.
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3. Multiple Choice Questions on Control System and Components
The section contains Control Systems MCQs on controller components, stepper motors, linear approximation of nonlinear systems, control system classification, hydraulic and pneumatic systems.
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4. Control System MCQ on Time Response Analysis, Design Specifications and Performance Indices
The section contains Control Systems MCQ questions and answers on standard test signals, time response of first and second order systems, steady state errors, performance indices, robotic control and state variable analysis.
5. Control System MCQ on Stability and Algebraic Criteria
The section contains Control System questions and answers on stability, conditions for stability, non-linear systems and routh-hurwitz stability criterion.
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6. Control System MCQ on Root Locus Technique
The section contains Control System MCQs on root locus and construction of root loci.
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7. Control System MCQ on Frequency Response Analysis
The section contains Control System multiple choice questions and answers on frequency response, polar and bode plots, pass and minimum phase systems, correlation between time and frequency response and transfer functions.
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8. Control System Multiple Choice Questions on Stability in Frequency Domain
The section contains Control System questions and answers on mathematical preliminaries, nyquist stability creation, closed loop frequency and time domain analysis.
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9. Control System MCQ on Design
The section contains Control System MCQs on design problems, cascade compensation in time domain as well as frequency domain, tuning of pid controllers, realization of basic compensators and feedback compensation.
10. MCQ on Digital Control Systems
The section contains Control System multiple choice questions and answers on signal reconstruction, z transform, z-transfer function, equations, z and s domain relationship, stability analysis and compensation techniques.
11. Control System MCQ on State Variable Analysis and Design
The section contains Control System questions and answers on concepts of state, state variables and state model, solutions of state equations, controllability and observability, pole placement by state feedback, observer systems and state models for linear continuous-time systems.
12. Control System MCQ on Liapunov’s Stability Analysis
The section contains Control System MCQs on liapunov’s stability criterion.
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13. Multiple Choice Questions on Optimal Control Systems
The section contains Control System multiple choice questions and answers on servomechanims, parameter optimization, optimal control and state regulator problems, output regulator tracking problem and infinite-time regulator problem.
14. Control System MCQ on Nonlinear Systems
The section contains Control System questions with answers on construction of phase trajectories, stability of nonlinear system and stability analysis by describing the functions.
15. MCQ on Advances in Control System
The section contains Control System MCQs on neural networks, adaptive control and fuzzy logic.
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16. Control System MCQ on Error Analysis
The section contains Control System multiple choice questions and answers on steady state error, integral square error and its minimization.
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Wish you the best in your endeavor to learn and master Control System!
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