This set of Control Systems Multiple Choice Questions & Answers (MCQs) focuses on “The Root Locus Concepts”.

1. Root locus of s(s+2)+K(s+4) =0 is a circle. What are the coordinates of the center of this circle?

a) -2,0

b) -3,0

c) -4,0

d) -5,0

2. The main objective of drawing root locus plot is :

a) To obtain a clear picture about the open loop poles and zeroes of the system

b) To obtain a clear picture about the transient response of feedback system for various values of open loop gain K

c) To determine sufficient condition for the value of ‘K’ that will make the feedback system unstable

d) Both b and c

3. Which one of the following statements is not correct?

a) Root loci can be used for analyzing stability and transient performance

b) Root loci provide insight into system stability and performance

c) Shape of the root locus gives idea of type of controller needed to meet design specification

d) Root locus can be used to handle more than one variable at a time

4. While increasing the value of gain K, the system becomes

a) Less stable

b) More stable

c) Unstable

d) Absolute stable

5. Root locus is used to calculate:

a) Marginal stability

b) Absolute stability

c) Conditional stability

d) Relative stability

6. Consider the following statements regarding root loci:

a) All root loci start from the respective poles of G(s) H(s)

b) All root loci end at the respective zeros of G(s) H(s) or go to infinity

c) The root loci are symmetrical about the imaginary axis of the s-plane

d) All root loci start and end from the respective poles of G(s) H(s) or go to infinity

7. The addition of open loop poles pulls the root locus towards:

a) The right and system becomes unstable

b) Imaginary axis and system becomes marginally stable

c) The left and system becomes unstable

d) The right and system becomes unstable

8. Routh Hurwitz criterion is better than root locus.

a) True

b) False

9. Number of roots of characteristic equation is equal to the number of ______________

a) Branches

b) Root

c) Stem

d) Poles

10. Which of the following statements are correct?

a) Root locus is for the negative feedback systems

b) Complementary root locus is for the positive feedback systems

c) Root locus is for the negative feedback and Complementary root locus is for the positive feedback systems

d) Complementary root locus is for the negative feedback systems