1. Which of the following is an inherent characteristic of an open-loop system?
A) The system possesses an electronic or mechanical feedback path.
B) The operational accuracy depends heavily on the initial calibration of the components.
C) It will automatically correct for load variation errors.
D) It is prone to self-induced oscillations due to excessive phase shift.
2. Introducing negative feedback to a control system expands which of the following performance metrics?
A) Maximum forward path gain
B) Overall system bandwidth
C) Parameter sensitivity factor
D) Total steady-state tracking error
3. If a system is described as operating with "regenerative feedback," it is utilizing:
A) Negative feedback
B) Positive feedback
C) Non-linear static feedforward
D) Zero-order hold feedback
4. What effect does negative feedback have on the noise introduced within the forward path of a control system?
A) It amplifies the noise by a factor of $(1 + GH)$.
B) It reduces the impact of the noise on the final output by a factor of $(1 + GH)$.
C) It completely eliminates the noise from the system at all frequencies.
D) It shifts the noise to the feedback sensor path.
5. An open-loop control system is generally preferred over a closed-loop system when:
A) Environmental disturbances are highly unpredictable.
B) System components are subject to rapid aging and drift.
C) Simple construction, lower cost, and absolute component stability are paramount.
D) Extremely high tracking accuracy is needed across a wide frequency range.
6. A system where the control action depends on a predictive model of a disturbance before it alters the output is known as a:
A) Closed-loop feedback system
B) Pure feedforward control system
C) Sampled-data adaptive loop
D) Multivariable regulator system
Section 2: Mathematical Modeling & Block Diagrams
7. If two sub-systems with transfer functions $G_1(s)$ and $G_2(s)$ are connected in a parallel configuration with a summing junction, the equivalent transfer function is:
A) $G_1(s) \times G_2(s)$
B) $G_1(s) + G_2(s)$
C) $\frac{G_1(s)}{G_2(s)}$
D) $\frac{G_1(s)G_2(s)}{1 + G_1(s)G_2(s)}$
8. If two sub-systems with transfer functions $G_1(s)$ and $G_2(s)$ are connected in series (cascade), 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) $G_1(s) - G_2(s)$
9. When moving a summing point from a position ahead of a block $G(s)$ to a position behind the block $G(s)$, the signal entering the summing point must be:
A) Divided by $G(s)$
B) Multiplied by $G(s)$
C) Kept unchanged
D) Inverted to $\frac{1}{G(s)}$
10. When moving a take-off point from a position ahead of a block $G(s)$ to a position behind the block $G(s)$, the extracted signal path must be modified by introducing a block equal to:
A) $G(s)$
B) $\frac{1}{G(s)}$
C) $1 - G(s)$
D) $G(s)^2$
11. For a closed-loop system with a forward path gain $G(s)$ and a positive feedback path gain $H(s)$, the closed-loop transfer function is:
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) $\frac{H(s)}{1 - G(s)H(s)}$
12. The mathematical phrase $G(s)H(s)$ in a single-loop feedback system represents the:
A) Closed-loop transfer function
B) Open-loop transfer function (or Loop Gain)
C) Error ratio function
D) Output sensitivity matrix
13. A unity feedback control system has a forward transfer function $G(s) = \frac{5}{s+3}$. What is its overall closed-loop transfer function?
A) $\frac{5}{s+3}$
B) $\frac{5}{s+8}$
C) $\frac{5}{s-2}$
D) $\frac{1}{s+8}$
14. The denominator polynomial of a closed-loop transfer function set to zero ($1 + G(s)H(s) = 0$) is defined as the:
A) Characteristic equation
B) State-space vector
C) Open-loop poles equation
D) Zero-mapping function
Section 3: Response Speed, Sensitivity & Stability
15. An open-loop system's response speed depends entirely on:
A) The controller gain adjustments made during runtime.
B) The natural time constants of its internal physical components.
C) The sampling frequency of the feedback loop sensor.
D) The error signal generated at the summing junction.
16. Compared to an open-loop system, a well-designed closed-loop system can track a rapidly changing input faster due to:
A) Reduced structural component weight.
B) Increased loop gain pushing the closed-loop poles farther into the left half-plane.
C) Eliminating the need for power amplification.
D) Operating exclusively with positive feedback margins.
17. The parameter sensitivity of a closed-loop system with respect to variations in the feedback path transfer function $H(s)$ is approximately:
A) Zero
B) Unity (1)
C) $\frac{1}{1+GH}$
D) Infinite
18. Why can a closed-loop control system experience instability while an open-loop system with the same plant remains stable?
A) Because closed-loop systems use more electrical power.
B) Because feedback can introduce excessive phase shift, turning negative feedback into positive feedback at high frequencies.
C) Because sensors naturally insert thermal noise into the system.
D) Because open-loop systems lack mathematical poles.
19. What type of controller can eliminate the steady-state tracking error of a closed-loop system responding to a constant step input?
A) A pure derivative controller
B) An integral controller block within the forward path
C) A high-pass filter in the feedback path
D) A static feedforward attenuator
20. A control system with a damping ratio $\zeta = 0$ will exhibit which type of transient response?
A) Overdamped exponential decay
B) Sustained, undamped sinusoidal oscillations
C) Critically damped rapid tracking
D) Unbounded exponential growth
Section 4: Field Applications & Physical Classification
21. An industrial conveyor belt moving at a fixed speed dictated solely by a manual voltage dial on a power supply is a/an:
A) Open-loop speed system
B) Closed-loop position regulator
C) Adaptive trajectory tracker
D) Continuous servo mechanism
22. If a heavy box lands on the conveyor belt in Question 21 and slows the belt down due to friction, what will the system do?
A) It will increase motor current automatically to maintain speed.
B) It will take no action, allowing the speed to stay lower because it has no sensor to measure actual belt velocity.
C) It will stop immediately and sound an error alarm.
D) It will reverse the motor direction.
23. An automated factory assembly system uses a tachometer to measure a motor's shaft speed and dynamically adjusts the power inverter frequency to maintain a constant rate. This is a:
A) Open-loop system
B) Closed-loop system
C) Discrete manual system
D) Static mathematical model
24. A domestic microwave oven that heats food for a user-specified duration of 2 minutes behaves as a/an:
A) Open-loop system
B) Closed-loop system
C) Temperature-regulated servo
D) Natural bio-feedback cascade
25. A human driver monitoring lane markers with their eyes and adjusting the steering wheel to keep a car centered is an example of:
A) An open-loop biological mechanism
B) A closed-loop control system where the human acts as the sensor and controller
C) A purely feedforward mechanical process
D) An uncontrolled random sequence
26. A basic automated automatic nightlight turns on at dusk and off at dawn by using a photo-resistor to monitor ambient light. This is a:
A) Open-loop system
B) Closed-loop system
C) Sampled-data optimal controller
D) Continuous tracking mechanism
27. A standard electric room heater controlled by a manual 3-position low/medium/high toggle switch operates as an:
A) Open-loop system
B) Closed-loop system
C) Autonomous climatic regulator
D) Multi-variable tracking matrix
28. An advanced laboratory incubator uses a resistance temperature detector (RTD) to adjust heating element duty cycles to keep an environment at exactly 37°C. This is a:
A) Open-loop system
B) Closed-loop system
C) Linear time-variant open process
D) Static feedforward matrix
Section 5: Advanced Loop Topologies & Terminology
29. In control terminology, a "servomechanism" refers specifically to a closed-loop system where the controlled output parameter is:
A) Chemical concentration or fluid pH
B) Mechanical position, velocity, or acceleration
C) Electrical voltage or current amplitude
D) Ambient room temperature
30. A closed-loop control configuration whose sole objective is to maintain a constant output value despite the presence of external load disturbances is called a:
A) Trajectory tracking system
B) Regulator system
C) Servomechanism
D) Open-ended sequencer
31. What is the core limitation of a combined feedforward-feedback control configuration?
A) It cannot achieve rapid response times.
B) The feedforward component requires explicit measurement or modeling of specific disturbances to counteract them, leaving unmodeled disturbances to be handled by the feedback loop.
C) It makes the entire system open-loop.
D) It reduces the total loop gain to zero.
32. A control architecture that automatically tunes its own controller parameters during real-time operations to compensate for structural shifts in plant dynamics is called an:
A) Invariant open-loop system
B) Adaptive control system
C) Static regulator loop
D) Uncompensated system
33. Which component performs the physical work required to adjust the plant's state based on low-power controller commands?
A) Summing junction
B) Transducer sensor
C) Actuator
D) Signal attenuator
34. In control theory, a system whose internal parameters change as a function of time is designated as:
A) Time-invariant
B) Time-variant
C) Static linear
D) Continuous-sample
Section 6: Comprehensive Performance Metrics
35. If high-frequency sensor noise enters the feedback path of a closed-loop system, it will:
A) Be completely blocked by the summing junction.
B) Be treated as an error by the controller, causing unwanted fluctuations in the system output.
C) Re-calibrate the open-loop gain parameters.
D) Shift the characteristic equation roots to zero.
36. Open-loop systems are fundamentally immune to feedback sensor noise because:
A) They use heavily shielded digital filters.
B) They lack a feedback path and sensors to transmit noise back into the controller input.
C) They run strictly on high-voltage DC power.
D) Their characteristic equations have no denominator.
37. If a minor modification in internal plant parameters results in a major distortion of the final output, the system exhibits:
A) High parameter sensitivity
B) Broad system bandwidth
C) High stability margin
D) Low tracking latency
38. Which system configuration allows an engineer to utilize less precise, lower-cost internal plant components while still achieving high accuracy at the final output?
A) Open-loop configuration
B) Closed-loop configuration
C) Cascade open-loop configuration
D) Non-linear feedforward configuration
39. What is a primary engineering challenge when deploying a closed-loop control system in highly remote or hazardous aerospace applications?
A) It cannot process differential equations.
B) The increased structural complexity, risk of loop instability, and the absolute requirement for highly robust, radiation-hardened sensors.
C) Its operational speed is too fast for telemetry networks.
D) It cannot operate without human operator oversight.
40. The mathematical equation describing the relationship between the reference input $R(s)$ and output $C(s)$ of an open-loop system is simply:
A) $C(s) = \frac{R(s)}{G(s)}$
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. If a wiring error inadvertently causes the feedback signal in a negative feedback system to be added to the reference input instead of subtracted, the system will operate under:
A) Enhanced regulation dynamics
B) Positive feedback conditions (leading to potential instability or saturation)
C) Zero bandwidth boundaries
D) Perfect tracking optimization
42. The engineering process of aligning an open-loop system's inputs to match known, correct output states under controlled laboratory settings is termed:
A) Digitization
B) Calibration
C) Demodulation
D) Linearization
43. Which of the following high-precision fields relies heavily on closed-loop servo mechanisms?
A) Standard household incandescence illumination
B) Multi-axis CNC machining and robotics
C) Manual analog hand tools
D) Standard mechanical wind-up timers
44. The parameter sensitivity of a closed-loop system with respect to variations in the forward path transfer function $G(s)$ is given by:
A) $\frac{1}{1 + G(s)H(s)}$
B) $1 + G(s)H(s)$
C) $\frac{G(s)}{1 + G(s)H(s)}$
D) $G(s)H(s)$
45. When a sudden step load disturbance acts directly on the output of a closed-loop system, the tracking error will initially:
A) Stay perfectly flat at zero.
B) Spike rapidly, then gradually decay toward zero as the feedback loop drives corrective action.
C) Grow infinitely without bound regardless of system type.
D) Cause the forward gain to plummet to zero instantly.
46. A system that shows an output response to an input signal with zero overshoot, zero ringing, and slow settling characteristics is described as:
A) Underdamped
B) Overdamped or Critically Damped
C) Unstable
D) Marginally oscillatory
47. What is the fundamental disadvantage of an open-loop system when handling structural component friction like backlash or stiction?
A) It will immediately experience infinite oscillations.
B) It cannot sense the resulting positional lag or offset, leading to uncorrected steady-state errors.
C) It will burn out the central processor unit.
D) It reduces the input reference voltage to zero.
48. Why are closed-loop architectures standard in automated industrial assembly operations despite higher costs?
A) They take up far less physical space.
B) They preserve high operational accuracy and repeatability despite component wear, temperature drift, and material variations.
C) They completely eliminate the need for mechanical actuators.
D) Open-loop systems are prohibited by safety codes.
49. A mathematical system where a single input signal controls a single output parameter is abbreviated as:
A) MIMO
B) SISO
C) LTI
D) BIBO
50. A system containing multiple sensors and multiple actuators whose inputs and outputs interact simultaneously is designated as a:
A) SISO system
B) MIMO system
C) Single-loop cascade
D) Decoupled open system
Answer Key
1 B | 2 B | 3 B | 4 B | 5 C
6 B | 7 B | 8 B | 9 B | 10 B
11 B | 12 B | 13 B | 14 A | 15 B
16 B | 17 B | 18 B | 19 B | 20 B
21 A | 22 B | 23 B | 24 A | 25 B
26 B | 27 A | 28 B | 29 B | 30 B
31 B | 32 B | 33 C | 34 B | 35 B
36 B | 37 A | 38 B | 39 B | 40 B
41 B | 42 B | 43 B | 44 A | 45 B
46 B | 47 B | 48 B | 49 B | 50 B
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