27 Control Systems questions from the Electrical Core bank, written for Indian campus drives and tech interviews. Every question has a verified answer and an AI-tutor explanation on placd.
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A.algebraic stability test where the number of sign changes in the first column of the Routh array equals the number of right-half-plane poles
B.proportional term for speed of response, integral to remove steady-state error, derivative to damp overshoot, commonly tuned by Ziegler-Nichols rules
C.ratio of the Laplace transform of output to that of input with zero initial conditions, valid for linear time-invariant systems
D.a state-space system is controllable when the matrix [B AB … A^(n−1)B] has full rank n, permitting arbitrary pole placement
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2. Which term means: "ratio of the Laplace transform of output to that of input with zero initial conditions, valid for linear time-invariant systems"?
Junior
A.Controllability
B.Transfer function
C.PID controller
D.Nyquist stability criterion
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3. Which statement is correct?
Junior
A.Transfer function — number of pure integrators (poles at the origin) in the open-loop transfer function, which decides steady-state error to step, ramp and parabolic inputs
B.Transfer function — closed loop is stable when the number of counter-clockwise encirclements of −1 equals the number of right-half-plane open-loop poles
C.Transfer function — additional phase lag at the gain crossover frequency that would bring the loop to the verge of instability, with 30–60° the usual design target
D.Transfer function — ratio of the Laplace transform of output to that of input with zero initial conditions, valid for linear time-invariant systems
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4. What is System type?
Junior
A.parameter ζ of a second-order system; below 1 underdamped, exactly 1 critically damped, with about 0.7 giving 5% overshoot
B.factor by which loop gain can be increased before instability, read at the phase crossover frequency where the phase is −180°
C.additional phase lag at the gain crossover frequency that would bring the loop to the verge of instability, with 30–60° the usual design target
D.number of pure integrators (poles at the origin) in the open-loop transfer function, which decides steady-state error to step, ramp and parabolic inputs
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5. Which term means: "number of pure integrators (poles at the origin) in the open-loop transfer function, which decides steady-state error to step, ramp and parabolic inputs"?
Junior
A.Controllability
B.Nyquist stability criterion
C.System type
D.Gain margin
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6. Which statement is correct?
Junior
A.System type — ratio of the Laplace transform of output to that of input with zero initial conditions, valid for linear time-invariant systems
B.System type — number of pure integrators (poles at the origin) in the open-loop transfer function, which decides steady-state error to step, ramp and parabolic inputs
C.System type — proportional term for speed of response, integral to remove steady-state error, derivative to damp overshoot, commonly tuned by Ziegler-Nichols rules
D.System type — algebraic stability test where the number of sign changes in the first column of the Routh array equals the number of right-half-plane poles
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7. What is Damping ratio?
Junior
A.additional phase lag at the gain crossover frequency that would bring the loop to the verge of instability, with 30–60° the usual design target
B.proportional term for speed of response, integral to remove steady-state error, derivative to damp overshoot, commonly tuned by Ziegler-Nichols rules
C.parameter ζ of a second-order system; below 1 underdamped, exactly 1 critically damped, with about 0.7 giving 5% overshoot
D.factor by which loop gain can be increased before instability, read at the phase crossover frequency where the phase is −180°
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8. Which term means: "parameter ζ of a second-order system; below 1 underdamped, exactly 1 critically damped, with about 0.7 giving 5% overshoot"?
Junior
A.Gain margin
B.Controllability
C.Phase margin
D.Damping ratio
Answer + AI explanation with Pro
9. Which statement is correct?
Junior
A.Damping ratio — number of pure integrators (poles at the origin) in the open-loop transfer function, which decides steady-state error to step, ramp and parabolic inputs
B.Damping ratio — parameter ζ of a second-order system; below 1 underdamped, exactly 1 critically damped, with about 0.7 giving 5% overshoot
C.Damping ratio — closed loop is stable when the number of counter-clockwise encirclements of −1 equals the number of right-half-plane open-loop poles
D.Damping ratio — factor by which loop gain can be increased before instability, read at the phase crossover frequency where the phase is −180°
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10. What is Routh-Hurwitz criterion?
Mid
A.number of pure integrators (poles at the origin) in the open-loop transfer function, which decides steady-state error to step, ramp and parabolic inputs
B.additional phase lag at the gain crossover frequency that would bring the loop to the verge of instability, with 30–60° the usual design target
C.algebraic stability test where the number of sign changes in the first column of the Routh array equals the number of right-half-plane poles
D.proportional term for speed of response, integral to remove steady-state error, derivative to damp overshoot, commonly tuned by Ziegler-Nichols rules
Answer + AI explanation with Pro
11. Which term means: "algebraic stability test where the number of sign changes in the first column of the Routh array equals the number of right-half-plane poles"?
Mid
A.Nyquist stability criterion
B.System type
C.Routh-Hurwitz criterion
D.Damping ratio
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12. Which statement is correct?
Mid
A.Routh-Hurwitz criterion — closed loop is stable when the number of counter-clockwise encirclements of −1 equals the number of right-half-plane open-loop poles
B.Routh-Hurwitz criterion — proportional term for speed of response, integral to remove steady-state error, derivative to damp overshoot, commonly tuned by Ziegler-Nichols rules
C.Routh-Hurwitz criterion — algebraic stability test where the number of sign changes in the first column of the Routh array equals the number of right-half-plane poles
D.Routh-Hurwitz criterion — additional phase lag at the gain crossover frequency that would bring the loop to the verge of instability, with 30–60° the usual design target
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13. What is Gain margin?
Mid
A.number of pure integrators (poles at the origin) in the open-loop transfer function, which decides steady-state error to step, ramp and parabolic inputs
B.additional phase lag at the gain crossover frequency that would bring the loop to the verge of instability, with 30–60° the usual design target
C.factor by which loop gain can be increased before instability, read at the phase crossover frequency where the phase is −180°
D.proportional term for speed of response, integral to remove steady-state error, derivative to damp overshoot, commonly tuned by Ziegler-Nichols rules
Answer + AI explanation with Pro
14. Which term means: "factor by which loop gain can be increased before instability, read at the phase crossover frequency where the phase is −180°"?
Mid
A.Damping ratio
B.System type
C.Gain margin
D.Nyquist stability criterion
Answer + AI explanation with Pro
15. Which statement is correct?
Mid
A.Gain margin — additional phase lag at the gain crossover frequency that would bring the loop to the verge of instability, with 30–60° the usual design target
B.Gain margin — a state-space system is controllable when the matrix [B AB … A^(n−1)B] has full rank n, permitting arbitrary pole placement
C.Gain margin — number of pure integrators (poles at the origin) in the open-loop transfer function, which decides steady-state error to step, ramp and parabolic inputs
D.Gain margin — factor by which loop gain can be increased before instability, read at the phase crossover frequency where the phase is −180°
Answer + AI explanation with Pro
16. What is Phase margin?
Mid
A.parameter ζ of a second-order system; below 1 underdamped, exactly 1 critically damped, with about 0.7 giving 5% overshoot
B.additional phase lag at the gain crossover frequency that would bring the loop to the verge of instability, with 30–60° the usual design target
C.closed loop is stable when the number of counter-clockwise encirclements of −1 equals the number of right-half-plane open-loop poles
D.a state-space system is controllable when the matrix [B AB … A^(n−1)B] has full rank n, permitting arbitrary pole placement
Answer + AI explanation with Pro
17. Which term means: "additional phase lag at the gain crossover frequency that would bring the loop to the verge of instability, with 30–60° the usual design target"?
Mid
A.Controllability
B.Phase margin
C.Gain margin
D.PID controller
Answer + AI explanation with Pro
18. Which statement is correct?
Mid
A.Phase margin — number of pure integrators (poles at the origin) in the open-loop transfer function, which decides steady-state error to step, ramp and parabolic inputs
B.Phase margin — algebraic stability test where the number of sign changes in the first column of the Routh array equals the number of right-half-plane poles
C.Phase margin — additional phase lag at the gain crossover frequency that would bring the loop to the verge of instability, with 30–60° the usual design target
D.Phase margin — a state-space system is controllable when the matrix [B AB … A^(n−1)B] has full rank n, permitting arbitrary pole placement
Answer + AI explanation with Pro
19. What is PID controller?
Mid
A.ratio of the Laplace transform of output to that of input with zero initial conditions, valid for linear time-invariant systems
B.number of pure integrators (poles at the origin) in the open-loop transfer function, which decides steady-state error to step, ramp and parabolic inputs
C.closed loop is stable when the number of counter-clockwise encirclements of −1 equals the number of right-half-plane open-loop poles
D.proportional term for speed of response, integral to remove steady-state error, derivative to damp overshoot, commonly tuned by Ziegler-Nichols rules
Answer + AI explanation with Pro
20. Which term means: "proportional term for speed of response, integral to remove steady-state error, derivative to damp overshoot, commonly tuned by Ziegler-Nichols rules"?
Mid
A.Routh-Hurwitz criterion
B.System type
C.Damping ratio
D.PID controller
Answer + AI explanation with Pro
21. Which statement is correct?
Mid
A.PID controller — a state-space system is controllable when the matrix [B AB … A^(n−1)B] has full rank n, permitting arbitrary pole placement
B.PID controller — number of pure integrators (poles at the origin) in the open-loop transfer function, which decides steady-state error to step, ramp and parabolic inputs
C.PID controller — factor by which loop gain can be increased before instability, read at the phase crossover frequency where the phase is −180°
D.PID controller — proportional term for speed of response, integral to remove steady-state error, derivative to damp overshoot, commonly tuned by Ziegler-Nichols rules
Answer + AI explanation with Pro
22. What is Nyquist stability criterion?
Senior
A.proportional term for speed of response, integral to remove steady-state error, derivative to damp overshoot, commonly tuned by Ziegler-Nichols rules
B.additional phase lag at the gain crossover frequency that would bring the loop to the verge of instability, with 30–60° the usual design target
C.closed loop is stable when the number of counter-clockwise encirclements of −1 equals the number of right-half-plane open-loop poles
D.ratio of the Laplace transform of output to that of input with zero initial conditions, valid for linear time-invariant systems
Answer + AI explanation with Pro
23. Which term means: "closed loop is stable when the number of counter-clockwise encirclements of −1 equals the number of right-half-plane open-loop poles"?
Senior
A.System type
B.Routh-Hurwitz criterion
C.Controllability
D.Nyquist stability criterion
Answer + AI explanation with Pro
24. Which statement is correct?
Senior
A.Nyquist stability criterion — a state-space system is controllable when the matrix [B AB … A^(n−1)B] has full rank n, permitting arbitrary pole placement
B.Nyquist stability criterion — parameter ζ of a second-order system; below 1 underdamped, exactly 1 critically damped, with about 0.7 giving 5% overshoot
C.Nyquist stability criterion — factor by which loop gain can be increased before instability, read at the phase crossover frequency where the phase is −180°
D.Nyquist stability criterion — closed loop is stable when the number of counter-clockwise encirclements of −1 equals the number of right-half-plane open-loop poles
Answer + AI explanation with Pro
25. What is Controllability?
Senior
A.additional phase lag at the gain crossover frequency that would bring the loop to the verge of instability, with 30–60° the usual design target
B.closed loop is stable when the number of counter-clockwise encirclements of −1 equals the number of right-half-plane open-loop poles
C.a state-space system is controllable when the matrix [B AB … A^(n−1)B] has full rank n, permitting arbitrary pole placement
D.parameter ζ of a second-order system; below 1 underdamped, exactly 1 critically damped, with about 0.7 giving 5% overshoot
Answer + AI explanation with Pro
26. Which term means: "a state-space system is controllable when the matrix [B AB … A^(n−1)B] has full rank n, permitting arbitrary pole placement"?
Senior
A.Controllability
B.Routh-Hurwitz criterion
C.Damping ratio
D.Phase margin
Answer + AI explanation with Pro
27. Which statement is correct?
Senior
A.Controllability — factor by which loop gain can be increased before instability, read at the phase crossover frequency where the phase is −180°
B.Controllability — ratio of the Laplace transform of output to that of input with zero initial conditions, valid for linear time-invariant systems
C.Controllability — number of pure integrators (poles at the origin) in the open-loop transfer function, which decides steady-state error to step, ramp and parabolic inputs
D.Controllability — a state-space system is controllable when the matrix [B AB … A^(n−1)B] has full rank n, permitting arbitrary pole placement
Answer + AI explanation with Pro
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