Home » Assessment of Relative Stability Using Nyquist Criterion
Multiple Choice Questions

Assessment of Relative Stability Using Nyquist Criterion

Assessment of Relative Stability Using Nyquist Criterion

1. The phase margin (in degrees) of a system having the loop transfer function G(s) H(s)=2√3/s(s+1) is:

a) 45°
b) -30°
c) 60°
d) 30°

Answer: d

Explanation: Phase margin is calculated at gain cross over frequency where magnitude of the transfer function is 1.

2. The system with the open loop transfer function G(s) H(s) =1/s(s^2+s+1) has the gain margin of :

a) -6 dB
b) 0 dB
c) 3.5 dB
d) 6 dB

Answer: b

Explanation: Gain margin is calculated at phase cross over frequency where the phase is 180°.

3. The phase angle of the system, G(s) =s+5/s<sup>2</sup>+4s+9, varies between :

a) 0° and 90°
b) 0° and -90°
c) 0° and -180°
d) -90° and -180°

Answer: a

Explanation: As it is the type 0 system so the phase angle can be 0° and 90°.

4. The polar plot of the transfer function G(s) = 10(s+1)/s+10 will be in the :

a) First quadrant
b) Second quadrant
c) Third quadrant
d) Fourth quadrant

Answer: d

Explanation: Polar plot of the given transfer function lies in the fourth quadrant.

5. As the polar plot moves toward the point (-1, 0) then the system becomes :

a) Stable
b) Marginally stable
c) Conditionally stable
d) Unstable

Answer: d

Explanation: As the polar plot moves toward the point (-1, 0) then the system becomes unstable.

6. Polar plots moving toward the imaginary axis makes the system:

a) Stable
b) Marginally stable
c) Conditionally stable
d) Unstable

Answer: d

Explanation: Polar plots moving toward the imaginary axis makes the system unstable.

7. The concepts used to measure relative stability are:

a) Phase margin
b) Gain margin
c) Phase and Gain margin
d) Stable

Answer: c

Explanation: The concepts used to measure relative stability are phase margin and gain margin.

8. Phase and gain margin are applicable to open and closed loop systems both.

a) True
b) False

Answer: b

Explanation: Phase and gain margin are applicable only to open loop systems.

9. Gain margin is:

a) It is a factor by which the system gain can be increased to drive it to the verge of instability
b) It is calculated at gain cross over frequency
c) It is calculated at phase cross over frequency
d) Both a and c

Answer: d

Explanation: Gain margin is a factor by which the system gain can be increased to drive it to the verge of instability and is calculated at phase cross over frequency.

10. Phase margin is:

a) It is amount of additional phase lag at the gain cross over frequency required to bring the system to the verge of instability
b) It is always positive for stable feedback systems
c) It is calculated at gain cross over frequency
d) All of the mentioned

Answer: d

Explanation: Phase margin is the measure of relative stability which is always positive for stable systems.

Similar Articles:

Related Articles

pH Meters Questions & Answers

S Bharadwaj Reddy

Fourier Transform NMR Spectroscopy Questions & Answers

S Bharadwaj Reddy

Ammonia and Fluoride Electrode Questions & Answers

S Bharadwaj Reddy

Pole Placement by State Feedback

S Bharadwaj Reddy

Stability of Nonlinear System – II

S Bharadwaj Reddy

Polar Plots MCQ

S Bharadwaj Reddy

Leave a Comment

This website uses cookies to improve your experience. We'll assume you're ok with this, but you can opt-out if you wish. Accept Read More

WordPress Image Lightbox