Nyquist Stability Criterion MCQ’s

This set of Control Systems Multiple Choice Questions & Answers (MCQs) focuses on “Nyquist Stability Criterion”.

1. If a Nyquist plot of G (jω) H (jω) for a closed loop system passes through (-2, j0) point in GH plane, what would be the value of gain margin of the system in dB?
a) 0 dB
b) 2.0201 dB
c) 4 dB
d) 6.0205 dB

2. For Nyquist contour, the size of radius is _______
a) 25
b) 0
c) 1
d) ∞

3. Which principle specifies the relationship between enclosure of poles & zeros by s-plane contour and the encirclement of origin by q(s) plane contour?
a) Argument
b) Agreement
c) Assessment
d) Assortment

4. Consider a feedback system with gain margin of about 30. At what point does Nyquist plot crosses negative real axis?
a) -3
b) -0.3
c) -30
d) -0.03

5. If the system is represented by G(s) H(s) = k (s+7) / s (s +3) (s + 2), what would be its magnitude at ω = ∞?
a) 0
b) ∞
c) 7/10
d) 21

6. Due to an addition of pole at origin, the polar plot gets shifted by ___ at ω = 0 ?
a) -45°
b) -60°
c) -90°
d) -180°

7. According to Nyquist stability criterion, where should be the position of all zeros of q(s) corresponding to s-plane?
a) On left half
b) At the center
c) On right half
d) Random

8. Consider the system represented by the equation given below. What would be the total phase value at ω = 0?
200/[s3 (s + 3) (s + 6) (s + 10)].
a) -90°
b) -180°
c) -270°
d) -360°

9. In polar plots, if a pole is added at the origin, what would be the value of the magnitude at Ω = 0?
a) Zero
b) Infinity
c) Unity
d) Unpredictable

10. In polar plots, what does each and every point represent w.r.t magnitude and angle?
a) Scalar
b) Vector
c) Phasor
d) Differentiator

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