Question

The phase angle of the system, G(s) =s+5/s^2+4s+9, varies between :

(a) 0° and 90°

(b) 0° and -90°

(c) 0° and -180°

(d) -90° and -180°

I had been asked this question during an interview.

Query is from Assessment of Relative Stability Using Nyquist Criterion topic in section Stability in Frequency Domain of Control Systems

Answer 1

Correct option is (a) 0° and 90°

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