Question

Which one of the following is not the property of root loci?

(a) The root locus is symmetrical about imaginary axis

(b) They start from the open loop poles and terminate at the open loop zeroes

(c) The breakaway points are determined from dK/ds = 0

(d) Segments of the real axis are the part of the root locus if and only is the total number of real poles and zeroes to their right is odd.

The question was posed to me in an interview for job.

This key question is from The Root Locus topic in portion The Root Locus Technique of Control Systems

Answer 1

Right answer is (a) The root locus is symmetrical about imaginary axis

The explanation: The root locus is the locus traced due to the gain of the system with changing frequency and need not be symmetrical about origin.