# Stability Analysis by Describing Functions MCQ’s

This set of Control Systems Multiple Choice Questions & Answers (MCQs) focuses on “Stability Analysis by Describing Functions”.

1. The root locus diagram has loop transfer function G(s)H(s) = K/ s(s+4)(s^{2}+4s+5) has

a) No breakaway points

b) Three real breakaway points

c) Only one breakaway points

d) One real and two complex breakaway points

2. For asymptotes passing from breakaway point then this point is also centroid

a) True

b) False

3. The characteristic equation of a feedback control system is given bys^{3}+5s^{2}+(K+6)s+K=0. In the root loci diagram, the asymptotes of the root loci for large K meet at a point in the s plane whose coordinates are:

a) (2,0)

b) (-1,0)

c) (-2,0)

d) (-3,0)

4. Transportation lag is seen in systems:

a) Amount to be transferred in large

b) Time take to transfer is large

c) Inefficiency of the process

d) Errors

5. Linear lumped parameter models are not valid under situations as:

a) Transmission pipe between the hydraulic pump and the motor causes a time lag in transportation of oil from pump to motor

b) Transmission of heat by conduction or convection produces serious transportation lag

c) Transmission pipe causes the time lag and loss of heat by conduction and convection

d) Transmission of pipe causes neither any time lag nor any heat loss

6. Transportation lag causes :

a) Instability in system

b) Stability in system

c) System remains unaffected

d) Bandwidth increases

7. Mediums responsible for transportation lag are:

a) Lines

b) Pipes

c) Belt conveyors

d) All of the mentioned

8. Practically all the systems have transportation lag :

a) True

b) False

9. The polar plot of a transfer function passes through the critical point (-1,0).Gain margin is

a) zero

b) -1dB

c) 1dB

d) Infinity

10. Consider the following statements:

1. The effect of feedback is to reduce the system error

2. Feedback increases the gain of the system in one frequency range but decreases in another.

3. Feedback can cause a system that is originally stable to become unstable

Which of these statements are correct.

a) 1,2 and 3

b) 1 and 2

c) 2 and 3

d) 1 and 3