1. : What is the main purpose of a control system?
(A) To increase system error
(B) To maintain the output at a desired level
(C) To create instability
(D) To reduce feedback
2. : A system in which output has no effect on the input signal is called:
(A) Closed-loop system
(B) Open-loop system
(C) Linear system
(D) Nonlinear system
3. : The open-loop transfer function of a system is given by:
(A) Product of all feedback gains
(B) Product of all forward path gains
(C) Ratio of output to input
(D) None of the above
4. : Which of the following is a closed-loop control system?
(A) Washing machine
(B) Traffic light
(C) Automatic temperature control
(D) Electric kettle
5. : Feedback in control systems is used to:
(A) Increase error
(B) Reduce the effect of disturbances
(C) Reduce accuracy
(D) Eliminate gain
6. : The transfer function of a system gives the relationship between:
(A) Input and output in time domain
(B) Input and output in Laplace domain
(C) Only input variables
(D) Only output variables
7. : The steady-state error of a Type-0 system for a step input is:
(A) Zero
(B) Finite
(C) Infinite
(D) Depends on gain
8. : The addition of poles to a transfer function generally:
(A) Increases system speed
(B) Decreases system speed
(C) Does not affect system response
(D) Improves stability
9. : Which plot shows how the roots of the characteristic equation vary with system gain?
(A) Nyquist plot
(B) Root locus
(C) Bode plot
(D) Polar plot
10. : For stability, the real parts of all closed-loop poles must be:
(A) Positive
(B) Negative
(C) Zero
(D) Any value
11. : The time constant of a first-order system is the time taken for the response to reach:
(A) 37% of final value
(B) 63% of final value
(C) 50% of final value
(D) 100% of final value
12. : The damping ratio (ζ) determines:
(A) Natural frequency
(B) System stability
(C) Transient response
(D) Both (B) and (C)
13. : The steady-state error for a ramp input in a Type-1 system is:
(A) Zero
(B) Finite
(C) Infinite
(D) Depends on gain
14. : A root locus branch always starts at:
(A) Zeros
(B) Poles
(C) Infinity
(D) Origin
15. : The Nyquist stability criterion is used to determine:
(A) Relative stability
(B) Absolute stability
(C) Frequency response
(D) Gain margin only
16. : The Bode plot is a graph between:
(A) Magnitude and phase vs frequency (log scale)
(B) Time and output
(C) Gain and time
(D) Phase and time
17. : If all poles of the transfer function lie in the left half of the s-plane, the system is:
(A) Stable
(B) Unstable
(C) Marginally stable
(D) Oscillatory
18. : Which component introduces a phase lead in a system?
(A) Inductor
(B) Capacitor
(C) Resistor
(D) Lead compensator
19. : The root locus branches terminate at:
(A) Zeros
(B) Poles
(C) Infinity
(D) Both (A) and (C)
20. : A system is said to be marginally stable if:
(A) Poles lie on the jω-axis
(B) Poles lie in the right half of s-plane
(C) Poles lie in the left half of s-plane
(D) Poles are at infinity
21. : Which test can be used to determine the stability of a system without calculating roots?
(A) Nyquist test
(B) Routh-Hurwitz criterion
(C) Bode plot
(D) Root locus
22. : The effect of derivative control is to:
(A) Increase rise time
(B) Reduce overshoot
(C) Increase steady-state error
(D) Reduce stability
23. : The integral control action reduces:
(A) Rise time
(B) Steady-state error
(C) Overshoot
(D) Stability
24. : The order of a system is determined by the:
(A) Number of zeros
(B) Number of poles
(C) Number of feedback loops
(D) Number of gains
25. : A second-order system has two poles at -2 and -3. The system is:
(A) Stable
(B) Unstable
(C) Marginally stable
(D) Oscillatory
26. : The phase margin is the additional phase required to reach:
(A) 0° phase
(B) -180° phase
(C) -90° phase
(D) -270° phase
27. : The gain margin is the factor by which gain can be multiplied before the system becomes:
(A) Stable
(B) Unstable
(C) Marginally stable
(D) Oscillatory
28. : The damping ratio ζ = 1 indicates:
(A) Underdamped system
(B) Critically damped system
(C) Overdamped system
(D) Oscillatory system
29. : If ζ = 0, the system response is:
(A) Overdamped
(B) Underdamped
(C) Critically damped
(D) Undamped (purely oscillatory)
30. : The bandwidth of a control system is a measure of:
(A) Speed of response
(B) Stability margin
(C) Gain margin
(D) Accuracy
31. : A lag compensator is used to:
(A) Increase bandwidth
(B) Reduce steady-state error
(C) Increase speed of response
(D) Decrease stability
32. : The phase lag introduced by a lag compensator is usually:
(A) Less than 90°
(B) 180°
(C) More than 90°
(D) None of the above
33. : The gain crossover frequency is the frequency where:
(A) Phase = -180°
(B) Gain = 0 dB
(C) Gain = 1 dB
(D) Phase = 0°
34. : The purpose of a PID controller is to:
(A) Improve transient and steady-state response
(B) Reduce bandwidth
(C) Increase delay
(D) Decrease gain
35. : The steady-state error of a Type-2 system to a ramp input is:
(A) Zero
(B) Finite
(C) Infinite
(D) Depends on K
36. : The rise time is defined as the time required for the response to rise from:
(A) 0% to 63%
(B) 0% to 90%
(C) 10% to 90%
(D) 0% to 100%
37. : Which of the following improves the speed of response?
(A) Lag compensator
(B) Lead compensator
(C) Integral controller
(D) Proportional controller
38. : The steady-state error for a parabolic input in a Type-1 system is:
(A) Zero
(B) Finite
(C) Infinite
(D) Depends on damping ratio
39. : The transient response of a system depends on:
(A) Poles of transfer function
(B) Zeros of transfer function
(C) Gain only
(D) None of the above
40. : A system with more number of poles than zeros is:
(A) Proper
(B) Improper
(C) Marginally stable
(D) Non-causal
41. : The final value theorem is used to determine:
(A) Initial value of the response
(B) Steady-state value of the response
(C) Transient value of the response
(D) None of the above
42. : The open-loop system becomes oscillatory at the frequency where:
(A) Phase = -90°
(B) Phase = -180° and gain = 0 dB
(C) Phase = 0°
(D) Gain = infinite
43. : In a Bode plot, each pole contributes:
(A) -20 dB/decade slope
(B) +20 dB/decade slope
(C) -10 dB/decade slope
(D) +10 dB/decade slope
44. : The unit impulse response of a system is the:
(A) Time response for a unit step input
(B) Inverse Laplace transform of transfer function
(C) Derivative of unit step response
(D) Both (B) and (C)