# 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