Open-Loop and Closed-Loop Control Systems — MCQs – EE

1. : Which of the following is an example of an open-loop control system?
(A) Electric iron
(B) Air conditioner
(C) Automatic voltage regulator
(D) Cruise control system

2. : In an open-loop control system, output:
(A) Has no effect on control action
(B) Has full effect on control action
(C) Is compared with input
(D) Controls the input directly

3. : A closed-loop control system is also known as:
(A) Manual control system
(B) Feedback control system
(C) Open control system
(D) Sequential control system

4. : In a closed-loop control system, feedback signal is proportional to:
(A) Input
(B) Output
(C) Error
(D) Disturbance

5. : The main advantage of a closed-loop control system over an open-loop one is:
(A) Low cost
(B) Simplicity
(C) Accuracy and automatic error correction
(D) High power consumption

6. : Which of the following is NOT a characteristic of open-loop systems?
(A) Easy to design
(B) Less accurate
(C) Sensitive to external disturbances
(D) Automatic error correction

7. : Which of the following is a closed-loop control system?
(A) Traffic light system
(B) Automatic washing machine
(C) Bread toaster
(D) Water tap

8. : In an open-loop system, output depends on:
(A) Input only
(B) Output only
(C) Feedback signal
(D) Disturbances

9. : The error detector in a closed-loop control system compares:
(A) Reference input and output
(B) Input and disturbance
(C) Output and feedback
(D) Forward and feedback path gains

10. : The feedback element in a closed-loop control system:
(A) Compares the reference input with the output
(B) Measures the output and feeds it back
(C) Amplifies the input
(D) Controls the actuator directly

11. : Which of the following systems does NOT require feedback?
(A) Automatic voltage regulator
(B) Cruise control system
(C) Electric toaster
(D) Temperature control system

12. : The disadvantage of a closed-loop control system is:
(A) Improved accuracy
(B) High stability
(C) Complexity and higher cost
(D) Error correction

13. : In a closed-loop system, if feedback gain increases, the overall gain of the system:
(A) Increases
(B) Decreases
(C) Remains constant
(D) Becomes zero

14. : Which statement best describes an open-loop system?
(A) It automatically corrects for disturbances
(B) It requires feedback for proper operation
(C) It cannot correct for disturbances
(D) It has a comparator

15. : A household refrigerator works as a:
(A) Open-loop control system
(B) Closed-loop control system
(C) Manual system
(D) Sequential system

16. : In a feedback control system, the function of the comparator is to:
(A) Compare output with feedback
(B) Compare input and output to produce an error signal
(C) Compare disturbance with input
(D) Compare gain and phase

17. : Feedback in a control system improves:
(A) Sensitivity
(B) Disturbance rejection
(C) Error amplification
(D) Instability

18. : In an open-loop system, changes in external conditions:
(A) Do not affect the output
(B) Affect the output considerably
(C) Improve accuracy
(D) Have no relation with output

19. : Which of the following is an example of a closed-loop control system?
(A) Electric bulb
(B) Speed control of DC motor using tachogenerator feedback
(C) Oven timer
(D) Hand-operated valve

20. : The block that measures the output and converts it to a feedback signal is called:
(A) Actuator
(B) Sensor
(C) Controller
(D) Comparator

21. : In an open-loop control system, stability is:
(A) Guaranteed
(B) Not guaranteed
(C) Always high
(D) Irrelevant

22. : A closed-loop control system generally has:
(A) Higher accuracy than open-loop
(B) Lower accuracy than open-loop
(C) No disturbance rejection
(D) No feedback element

23. : The primary disadvantage of open-loop systems is:
(A) High cost
(B) Inability to correct for disturbances
(C) Complexity
(D) Need for sensors

24. : The thermostat in an air conditioning system acts as a:
(A) Feedback sensor
(B) Actuator
(C) Comparator
(D) Amplifier

25. : The human body’s temperature regulation mechanism is an example of:
(A) Open-loop system
(B) Closed-loop system
(C) Manual control
(D) Open-circuit system

26. : In a closed-loop control system, the output is:
(A) Independent of input
(B) Dependent on input and feedback
(C) Dependent only on feedback
(D) Independent of disturbances

27. : The main function of feedback in a control system is to:
(A) Increase sensitivity
(B) Reduce error
(C) Increase gain
(D) Increase noise

28. : Open-loop systems are generally used where:
(A) High accuracy is required
(B) System output changes frequently
(C) Disturbances are negligible
(D) Continuous feedback is required

29. : The stability of a closed-loop control system mainly depends on:
(A) Forward path gain
(B) Feedback path
(C) Pole locations of the closed-loop transfer function
(D) Number of sensors