1. Which of the following statements is true regarding the stability of an open-loop system?
A) It can become unstable if the feedback loop has too much delay.
B) It is inherently stable if all its individual components are stable.
C) It will always oscillate if the input is a step function.
D) Its stability depends heavily on the feedback sensor's resolution.
2. In the presence of a constant forward-path disturbance, a closed-loop system with which type of controller can eliminate steady-state error completely?
A) Proportional (P) controller
B) Integral (I) controller
C) Derivative (D) controller
D) Feedforward-only controller
3. How does the addition of a negative feedback loop affect the system's sensitivity to variations in the forward-path transfer function $G(s)$?
A) It increases sensitivity by a factor of $(1 + GH)$.
B) It reduces sensitivity by a factor of $(1 + GH)$.
C) It makes sensitivity entirely independent of $G(s)$.
D) It doubles the sensitivity at all operating frequencies.
4. What happens to the overall system tracking error as the loop gain $G(s)H(s)$ becomes extremely small (approaches zero)?
A) The tracking error approaches zero.
B) The tracking error approaches its maximum value (the output fails to follow the input).
C) The system becomes infinitely fast.
D) The feedback signal perfectly matches the reference input.
5. Which system structure is more vulnerable to permanent calibration drift caused by component aging?
A) Closed-loop system
B) Open-loop system
C) Both are affected equally
D) Neither, as aging only affects physical housing
6. Regenerative feedback is another term for:
A) Degenerative feedback
B) Negative feedback
C) Positive feedback
D) Optimal feedback
Section 2: Mathematical Foundations & Block Diagrams
7. If two blocks with transfer functions $G_1(s)$ and $G_2(s)$ are connected in a parallel configuration, the equivalent transfer function is:
A) $G_1(s) \times G_2(s)$
B) $G_1(s) / G_2(s)$
C) $G_1(s) + G_2(s)$
D) $G_1(s) - G_2(s)$
8. If two blocks with transfer functions $G_1(s)$ and $G_2(s)$ are connected in cascade (series), the equivalent transfer function is:
A) $G_1(s) + G_2(s)$
B) $G_1(s) \times G_2(s)$
C) $\frac{G_1(s)}{G_2(s)}$
D) $\frac{1}{G_1(s)} + \frac{1}{G_2(s)}$
9. When moving a summing point ahead of a block $G(s)$ (moving it from the output side to the input side of the block), the signal entering the summing point must be:
A) Multiplied by $G(s)$
B) Divided by $G(s)$
C) Subtracted from $G(s)$
D) Left unchanged
10. When moving a take-off point ahead of a block $G(s)$ (moving it from the output side to the input side of the block), the extracted signal path must be modified by adding a block equal to:
A) $G(s)$
B) $\frac{1}{G(s)}$
C) $1 - G(s)$
D) $G(s)^2$
11. For a non-unity negative feedback system with forward gain $G$ and feedback gain $H$, what is the feedback signal $B$ equal to in terms of output $C$?
A) $B = C / H$
B) $B = C \times H$
C) $B = C - H$
D) $B = G \times H$
12. The term "Loop Gain" specifically refers to which mathematical product in a single-loop feedback system?
A) $\frac{G(s)}{1+G(s)H(s)}$
B) $G(s)H(s)$
C) $1 + G(s)H(s)$
D) $\frac{1}{G(s)H(s)}$
13. If a closed-loop system's characteristic equation is given by $s^2 + 3s + 2 = 0$, what are the closed-loop poles of the system?
A) $s = 1, 2$
B) $s = -1, -2$
C) $s = 0, -3$
D) $s = -1, -3$
14. A unity feedback system has a forward transfer function $G(s) = \frac{10}{s+2}$. What is its closed-loop transfer function?
A) $\frac{10}{s+2}$
B) $\frac{10}{s+12}$
C) $\frac{10}{s-8}$
D) $\frac{1}{s+12}$
Section 3: System Response & Performance
15. A system bandwidth can be conceptually expanded by incorporating:
A) Higher load resistance
B) Negative feedback
C) Positive feedback
D) Additional time delays
16. Which type of system generally exhibits a faster initial response speed if all internal plant components are identical?
A) A poorly calibrated open-loop system
B) A properly designed closed-loop system with high forward gain
C) A unity feedback system with low loop gain
D) A completely passive open-loop system
17. Non-linearities like "Dead Zone" or "Saturation" cause severe output distortion. How does a closed-loop system mitigate this compared to an open-loop design?
A) It physically removes the non-linear component from the plant.
B) The feedback path continuously senses the distorted output and forces the controller to over-drive or correct the input signal to compensate.
C) It converts the non-linear process into a purely digital signal.
D) It limits the bandwidth to zero.
18. The "Transient Response" of a control system refers to the behavior of the output signal:
A) Long after the input signal has stabilized to a constant value.
B) During the initial state transition from the starting point to the final settled value.
C) Only when the system is switched off.
D) When the feedback loop is completely broken.
19. "Steady-State Response" refers to the behavior of the system output as time ($t$) approaches:
A) Zero
D) Infinity
C) The system time constant ($\tau$)
D) The sampling interval
20. High loop gain in a closed-loop system achieves which of the following results?
A) Higher steady-state error and lower power consumption.
B) Lower steady-state error and better disturbance rejection.
C) Complete immunity to sensor noise.
D) Guaranteed absolute stability under all conditions.
Section 4: Real-World Applications & Edge Cases
21. An industrial stepper motor rotating exactly 90 degrees based solely on a designated number of electrical pulses sent from a micro-controller is operating as a/an:
A) Closed-loop position system
B) Open-loop position system
C) Continuous feedback regulator
D) Adaptive process loop
22. If the stepper motor in Question 21 encounters an unexpected mechanical jam mid-rotation, what will happen?
A) The micro-controller will detect the jam and increase current automatically.
B) The system will continue sending pulses assuming the motor is moving, resulting in an uncorrected positional error.
C) The system will immediately throw a feedback tracking error code.
D) The motor will reverse direction automatically.
23. A modern printing press uses an optical encoder attached to the motor shaft to measure exact rotational positions and adjust input voltage dynamically. This is a:
A) Manual control system
B) Closed-loop control system
C) Feedforward open-loop system
D) Time-delayed open-loop process
24. A standard automatic coffee maker brews coffee based on a structural water heating sequence and a gravity drip mechanism. This behaves as a/an:
A) Open-loop system
B) Closed-loop system
C) Multivariable tracking system
D) Bio-feedback mechanism
25. A human operator adjusting a valve manually to keep the water level in a tank at a specific line by looking at a sight glass is acting as the:
A) Actuator and plant
B) Controller and feedback sensor
C) Disturbance signal
D) Setpoint reference parameter
26. A hand drier that turns on when you place your hands under it and turns off immediately when you remove them using an infrared proximity sensor is a:
A) Open-loop system
B) Closed-loop system
C) Continuous servo system
D) Non-linear adaptive system
27. Why is a standard desk lamp controlled by an On/Off toggle switch classified as an open-loop system?
A) It lacks an internal electrical fuse.
B) It does not monitor the actual ambient light level in the room to decide whether to change its brightness.
C) It operates on alternating current (AC).
D) It cannot be integrated into a smart home network.
28. A smart solar panel tracking system uses light-dependent resistors (LDRs) to measure sun position and rotate the panels to maximize energy absorption. This is a:
A) Open-loop system
B) Closed-loop system
C) Static process model
D) Linear time-invariant open system
Section 5: Advanced Control Typologies & Terminology
29. What type of control system uses a mathematical model of a disturbance to counteract it before it affects the system output?
A) Feedback control system
B) Feedforward control system
C) Cascade open system
D) Hysteresis control system
30. A combined feedforward-feedback control configuration provides what major advantage?
A) It eliminates the need for any sensors.
B) The feedforward loop handles major known disturbances quickly, while the feedback loop corrects for remaining errors and unmeasured disturbances.
C) It reduces the system cost to zero.
D) It turns a closed-loop system into a purely open-loop structure.
31. A control system where the controller parameters are automatically adjusted in real-time to cope with large changes in plant dynamics is called a/an:
A) Rigid open-loop system
B) Adaptive control system
C) Static regulator system
D) Linear multi-loop system
32. Which of the following is an example of an electrical "transducer" commonly used in the feedback path of a speed control loop?
A) DC Motor
B) Tachogenerator
C) Power Transistor
D) Solenoid Valve
33. In control system terminology, the "plant" refers to:
A) The biological asset surrounding the laboratory.
B) The physical equipment, mechanism, or process that is being controlled.
C) The microprocessor executing the control code.
D) The user interface display terminal.
34. A system whose parameters do not change with time is explicitly designated as a:
A) Time-variant system
B) Time-invariant system
C) Continuous-sample system
D) Non-linear static system
Section 6: Deep-Dive Comparative Metrics
35. Sensor noise introduced directly into the feedback path of a closed-loop system will:
A) Be completely rejected by the controller.
B) Appear as an error at the summing junction and corrupt the output response.
C) Turn the system into an open-loop architecture.
D) Increase the overall forward-path gain.
36. Why are open-loop systems completely immune to sensor noise in their control path?
A) Because they use higher quality copper wiring.
B) Because they do not possess a feedback loop or sensors to feed noise back into the system.
C) Because they operate strictly on analog signals.
D) Because they are always shielded by metal enclosures.
37. If a system's output changes significantly with minor ambient temperature variations, the system has:
A) High parameter sensitivity
B) High bandwidth accuracy
C) Infinite phase margin
D) High stability margins
38. Which configuration allows an engineer to use cheaper, less precise internal components within the plant while still maintaining high final accuracy?
A) Open-loop configuration
B) Closed-loop configuration
C) No configuration can achieve this
D) Cascade open-loop configuration
39. What is the main structural bottleneck of implementing a closed-loop control system in a remote, hazardous space environment?
A) It cannot work without a manual switch.
B) The high complexity, necessity of robust, radiation-hardened sensors, and potential for loop instability.
C) It operates too fast for telemetry data.
D) It cannot be mathematically modeled using differential equations.
40. The mathematical equation describing the relationship between the input and output of an open-loop system is simply:
A) $C(s) = R(s) / G(s)$
B) $C(s) = R(s) \times G(s)$
C) $C(s) = \frac{R(s)G(s)}{1+G(s)}$
D) $C(s) = R(s) + G(s)$
41. In a negative feedback system, if the feedback loop signal is added instead of subtracted due to a wiring error, the system will instantly shift to operating with:
A) Enhanced steady-state regulation
B) Positive feedback dynamics
C) Zero bandwidth performance
D) Perfect tracking accuracy
42. The process of configuring an open-loop system's inputs to produce known correct outputs under ideal conditions is called:
A) Digitization
B) Calibration
C) Optimization
D) Demodulation
43. Which of the following fields relies heavily on closed-loop servo mechanisms for high-precision operations?
A) Standard incandescent lighting
B) Industrial Robotics and CNC Machining
C) Conventional manual hand tools
D) Fixed-cycle domestic lawn sprinklers
44. When evaluating the sensitivity of a closed-loop system to feedback path variations ($H$), the sensitivity is approximately equal to:
A) Zero
B) Unity (1)
C) $\frac{1}{1+GH}$
D) Infinite
45. A closed-loop system is tracking a reference signal. If a sudden step load disturbance occurs directly at the output plant, the error signal will initially:
A) Remain entirely at zero.
B) Spike up or down, then decrease as the feedback loop drives the system to correct itself.
C) Keep growing infinitely without bounds regardless of loop gain.
D) Cause the forward-path gain to drop to zero.
46. The denominator of a closed-loop transfer function equated to zero ($1 + G(s)H(s) = 0$) is structurally known as the:
A) Open-loop transfer function
B) Characteristic equation
C) System numerator polynomial
D) Feedback scalar baseline
47. A system with a complex, non-linear forward path can be linearized effectively around an operating point by implementing:
A) High-voltage open-loop controllers
B) Negative feedback loops
C) Long cascade delay pipelines
D) Positive feedback loops
48. If a control system responds to an input command with zero overshoot and zero oscillations, it is considered:
A) Underdamped
B) Overdamped or Critically Damped
C) Unstable
D) Marginally stable
49. What is the fundamental disadvantage of an open-loop system when handling non-linear component friction?
A) It will oscillate uncontrollably.
B) It cannot detect the resulting slowing effect or position offset, leading to uncorrected errors in the final output.
C) It will burn out the microprocessor.
D) It reduces the structural input voltage to zero.
50. In an industrial automated assembly line, why is a closed-loop system preferred over an open-loop system despite the higher initial cost?
A) Because it consumes less floor space.
B) Because it provides consistent precision and self-correction despite unpredictable machine wear, material variations, and temperature fluctuations.
C) Because it completely eliminates the need for electrical actuators.
D) Because open-loop systems are illegal to operate in manufacturing zones.
Answer Key
1 B | 2 B | 3 B | 4 B | 5 B
6 C | 7 C | 8 B | 9 B | 10 B
11 B | 12 B | 13 B | 14 B | 15 B
16 B | 17 B | 18 B | 19 B | 20 B
21 B | 22 B | 23 B | 24 A | 25 B
26 B | 27 B | 28 B | 29 B | 30 B
31 B | 32 B | 33 B | 34 B | 35 B
36 B | 37 A | 38 B | 39 B | 40 B
41 B | 42 B | 43 B | 44 B | 45 B
46 B | 47 B | 48 B | 49 B | 50 B
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