27 real Control Systems questions from the Electrical Core bank, as asked in Indian campus drives and tech interviews. Every question has a verified answer and an AI-tutor explanation on placd — free to start.
1. What is Transfer function?
Junior
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
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"?
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
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
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"?
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
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°
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°
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
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"?
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
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
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°
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"?
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
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
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"?
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
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
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"?
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
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
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