Question

If the Nyquist plot of the loop transfer function G (s)H (s) of a closed-loop system encloses the (1, j0) point in the G (s)H (s) plane, the gain margin of the system is

(a) Zero

(b) Greater than zero

(c) Less than zero

(d) Infinity

This question was addressed to me during an internship interview.

My doubt is from Experimentation of Transfer Function topic in section Frequency Response Analysis of Control Systems

Answer 1

Correct option is (c) Less than zero

The best I can explain: Nyquist plot deals with the open loop poles and zero and equals the encirclements to the open loop poles of the system.