1. Which of the following best describes an open-loop control system?
A) A system where the output has a direct effect on the control action.
B) A system in which the control action is totally independent of the output.
C) A system that uses a feedback loop to minimize errors.
D) A system that cannot be manually controlled.
2. A closed-loop control system is also commonly referred to as a:
A) Non-feedback control system
B) Feedback control system
C) Linear-only control system
D) Manual control system
3. What is the primary purpose of feedback in a control system?
A) To increase the overall physical size of the system.
B) To reduce the system's response to disturbances and improve accuracy.
C) To eliminate the need for an input signal.
D) To make the system entirely open-loop.
4. In a control system, the "setpoint" represents:
A) The actual output measured by a sensor.
B) The maximum limit the system can tolerate.
C) The desired or reference value of the output variable.
D) The time it takes for the system to start.
5. Which of the following expressions correctly represents the error signal ($e$) in a basic negative feedback system? (Where $r$ = reference input, $b$ = feedback signal)
A) $e = r \times b$
B) $e = r + b$
C) $e = r - b$
D) $e = b - r$
6. An open-loop system is generally chosen over a closed-loop system when:
A) Extremely high accuracy is required under unpredictable conditions.
B) Operating conditions are predictable and calibration is easy.
C) The system output must constantly change based on environmental noise.
D) Stability is a major issue in the process.
7. What happens to a closed-loop system if the feedback path is broken?
A) It becomes an open-loop system.
B) It doubles its accuracy.
C) It completely stops drawing electrical power.
D) It begins to self-oscillate infinitely.
8. The transfer function of a system is defined as the ratio of the Laplace transform of the output to the Laplace transform of the input under what condition?
A) Maximum input voltage
B) Zero initial conditions
C) Infinite time domain
D) Constant feedback gain
Section 2: System Components & Signal Flow
9. Which component in a closed-loop system directly measures the controlled output variable?
A) Actuator
B) Controller
C) Sensor / Transducer
D) Amplifier
10. The role of an "actuator" in a control system is to:
A) Compare the reference input with the feedback signal.
B) Convert the low-power control signal into a physical action on the plant.
C) Convert a physical quantity into an electrical signal.
D) Filter out high-frequency noise from the system.
11. In a block diagram of a closed-loop system, the circle with a cross or a summation sign inside it is called a:
A) Take-off point
B) Branch point
C) Comparator or Summing junction
D) Gain block
12. What is a "take-off point" in a block diagram?
A) The point where the system shuts down safely.
B) A point from which a signal is taken to be fed into another block or loop.
C) The physical location of the actuator.
D) The ground connection of the control circuit.
13. What type of feedback is most commonly used in practical stabilization control systems?
A) Positive feedback
B) Negative feedback
C) Zero feedback
D) Regenerative feedback
14. Positive feedback in a control system typically leads to:
A) Decreased sensitivity and higher stability.
B) Increased stability and faster settling times.
C) Instability, saturation, or oscillation.
D) Perfect tracking of the input signal.
15. If a closed-loop system has a forward path gain $G(s)$ and a feedback path gain $H(s)$, what is its overall closed-loop transfer function for negative feedback?
A) $\frac{G(s)}{1 - G(s)H(s)}$
B) $\frac{G(s)}{1 + G(s)H(s)}$
C) $G(s) \times H(s)$
D) $\frac{H(s)}{1 + G(s)H(s)}$
16. In the transfer function formula for positive feedback, the denominator becomes:
A) $1 + G(s)H(s)$
B) $1 - G(s)H(s)$
C) $G(s)H(s)$
D) $1$
Section 3: Advantages, Disadvantages & Performance Metrics
17. Which of the following is a key advantage of an open-loop system?
A) Highly accurate even in changing environments.
B) Automatically corrects for system wear and tear.
C) Simple construction, lower cost, and easy maintenance.
D) Never requires calibration.
18. Why do closed-loop systems require regular engineering analysis for "stability"?
A) Because they lack sufficient power to run indefinitely.
B) Because feedback can cause the system to overcorrect and go into wild oscillations.
C) Because sensors naturally heat up the circuit over time.
D) Because open-loop configurations are naturally more unstable.
19. How does negative feedback affect the overall gain of a control system?
A) It increases the gain.
B) It reduces the gain.
C) It makes the gain infinite.
D) It has absolutely no effect on the gain.
20. Negative feedback has the beneficial effect of:
A) Decreasing the bandwidth of the system.
B) Increasing the system's sensitivity to parameter variations.
C) Increasing the bandwidth and reducing sensitivity to parameter changes.
D) Increasing distortion and non-linearities.
21. "Sensitivity" of a control system refers to:
A) How fragile the physical components are to drop damage.
B) The degree to which the system's performance changes due to variations in its internal parameters.
C) The speed at which the sensor transmits data.
D) The price ratio between sensors and actuators.
22. Open-loop systems are highly sensitive to:
A) Changes in input command only.
B) Parameter variations and external environmental disturbances.
C) The frequency of the feedback signal.
D) Instability and oscillatory bursts.
23. Bandwidth in a control system measures:
A) The weight of the controller components.
B) The range of frequencies over which the system can track commands effectively.
C) The data transfer rate of the network cable.
D) The maximum voltage threshold of the feedback element.
24. Compared to open-loop systems, closed-loop systems are generally:
A) Cheaper to design and install.
B) Less complex with fewer components.
C) More complex, expensive, and require more maintenance.
D) Free from any possibility of tracking errors.
Section 4: Real-World Applications & Identification
25. A traffic light operating purely on a pre-programmed time delay is an example of an:
A) Open-loop system
B) Closed-loop system
C) Adaptive system
D) Intelligent system
26. A smart traffic light system that adjusts its green-light duration based on real-time cameras measuring vehicle density is a:
A) Open-loop system
B) Closed-loop system
C) Manual override system
D) Non-linear static system
27. An automatic air conditioning system that reads the room temperature and turns on the compressor to maintain a steady 22°C is a:
A) Open-loop system
B) Closed-loop system
C) Servo motor mechanism
D) Continuous manual system
28. A ceiling fan controlled by a manual 5-speed rotary knob regulator behaves as an:
A) Open-loop system
B) Closed-loop system
C) Autonomous system
D) Optimal control system
29. An automobile cruise control system adjusts the throttle position to maintain a steady speed when going uphill. This is an application of:
A) Open-loop control
B) Closed-loop control
C) Digital open-ended control
D) Discontinuous feed-forward control
30. Why is a standard electric clothes dryer considered an open-loop system?
A) It consumes too much electricity to run feedback circuits.
B) It dries clothes using a preset timer, regardless of whether the clothes are still damp or bone dry.
C) It adjusts its heat based on a moisture sensor.
D) It uses an electric motor to spin the drum.
31. A modern high-end clothes dryer that includes a sensor to detect moisture levels and stops running once the clothes are dry is a:
A) Non-linear open-loop system
B) Closed-loop system
C) Manual control process
D) Static mathematical model
32. Human body temperature regulation (sweating when hot, shivering when cold) is a natural example of:
A) Open-loop control system
B) Closed-loop control system
C) Uncontrolled biological process
D) Positive feedback cascade
33. A missile guidance system that constantly tracks a moving target and adjusts its fins mid-flight is operating as a:
A) Closed-loop system
B) Open-loop system
C) Stationary system
D) Feed-forward only system
34. Switching on a manual light switch to illuminate a dark room is a classic example of:
A) Open-loop manual control
B) Closed-loop automatic control
C) Multivariable adaptive loop
D) Sampled data control
Section 5: Advanced Control Concepts & Distinctions
35. What is an "external disturbance" in a control system?
A) The primary input signal fed by the operator.
B) An unwanted, unpredictable signal that tends to adversely affect the value of the controlled output.
C) The deliberate adjustment of controller gains.
D) The electrical ground reference point.
36. Which type of system is fundamentally better at rejecting external disturbances?
A) Open-loop system
B) Closed-loop system
C) Both reject disturbances equally
D) Neither can reject disturbances
37. Non-linearities (such as friction, gear backlash, and saturation) are harder to manage in:
A) Closed-loop systems due to instability risks.
B) Open-loop systems because they can never compensate for the resulting errors.
C) Neither, as non-linearities do not impact control accuracy.
D) Systems that only use mechanical linkages.
38. What is a "servomechanism" (or Servo system)?
A) Any open-loop system that operates under high voltage.
B) A closed-loop control system where the output is a mechanical position, velocity, or acceleration.
C) A type of manual kitchen appliance.
D) An ancient mechanical lever system.
39. A "regulator" system is a specific type of closed-loop system designed to:
A) Continuously track a rapidly changing input signal.
B) Keep a controlled output constant at a desired setpoint despite external disturbances.
C) Increase its output to infinity over time.
D) Convert AC power to DC power exclusively.
40. What is the fundamental limitation of a purely feed-forward control system compared to a feedback system?
A) It responds too slowly to inputs.
B) It requires a sensor to measure the output.
C) It can only compensate for disturbances that are explicitly measured, leaving unmeasured variations uncorrected.
D) It always causes loop instability.
41. In control engineering, a "SISO" system stands for:
A) Signal In, Signal Out
B) Single-Input, Single-Output
C) Synchronous-Input, Series-Output
D) System-Internal, Sensor-Optimized
42. A system that has multiple sensors and multiple actuators interacting simultaneously is called a:
A) SISO system
B) MIMO (Multiple-Input, Multiple-Output) system
C) Duplex open-loop system
D) Uni-directional loop
Section 6: Comparative Analysis & Problem Solving
43. If an open-loop system's components experience physical wear and calibration drifts over time, the system's output will:
A) Stay perfectly accurate.
B) Automatically recalibrate.
C) Drift away from the intended value without the system realizing it.
D) Immediately cause an emergency shut down.
44. Which of the following statements is TRUE regarding calibration?
A) Closed-loop systems require much more frequent recalibration than open-loop systems.
B) Open-loop systems rely heavily on precise, upfront calibration to preserve accuracy.
C) Calibration is completely unnecessary for open-loop systems.
D) Feedback systems cease working entirely if the initial calibration is slightly off.
45. The parameter $(1 + G(s)H(s))$ in a negative feedback system is commonly referred to as the:
A) Characteristic polynomial / loop determinant
B) Open-loop system gain
C) Feedback scalar unit
D) Forward path constant
46. By setting the characteristic equation $1 + G(s)H(s) = 0$, control engineers can evaluate a closed-loop system's:
A) Physical dimensions
B) Total power consumption
C) Absolute stability and pole locations
D) Manufacturing cost
47. Which design choice is most likely to reduce the steady-state tracking error of a closed-loop system?
A) Removing the feedback sensor entirely.
B) Lowering the loop gain to zero.
C) Increasing the loop gain or introducing an integrator block.
D) Adding a time delay into the feedback path.
48. If the loop gain $G(s)H(s)$ of a negative feedback system approaches infinity, the overall closed-loop transfer function reduces approximately to:
A) $G(s)$
B) $\frac{1}{H(s)}$
C) $H(s)$
D) Zero
49. An ideal control system should possess which of the following combined traits?
A) High sensitivity to noise, narrow bandwidth, low stability.
B) Zero speed, infinite tracking error, high cost.
C) Low sensitivity to parameter variations, high disturbance rejection, and adequate stability margins.
D) Complete open-loop structure with positive feedback loops.
50. Which of the following is an example of an open-loop process that can be turned into a closed-loop process by introducing a human operator?
A) An automated industrial robot arm tracking coordinates.
B) A driver steering a car along a winding road by watching the lane markers.
C) A pre-programmed washing machine spinning clothes.
D) A digital alarm clock ringing at 6:00 AM.
1 B | 2 B | 3 B | 4 C | 5 C
6 B | 7 A | 8 B | 9 C | 10 B
11 C | 12 B | 13 B | 14 C | 15 B
16 B | 17 C | 18 B | 19 B | 20 C
21 B | 22 B | 23 B | 24 C | 25 A
26 B | 27 B | 28 A | 29 B | 30 B
31 B | 32 B | 33 B | 34 A | 35 B
36 B | 37 B | 38 B | 39 B | 40 C
41 B | 42 B | 43 C | 44 B | 45 A
46 C | 47 C | 48 B | 49 C | 50 B
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