Question

According to Nyquist stability criterion, the number of unstable closed-loop poles (Z) is equal to:

• A. N - P
• B. N + P
• C. P - N
• D. N × P

Hint:

Nyquist formula: Z = N − P.

Answer 1

The Correct Option is A

Concept: Nyquist criterion states: \[ Z = N - P \] Where:
• $Z$ = number of closed-loop poles in right half plane
• $N$ = number of encirclements of -1 point
• $P$ = number of open-loop poles in right half plane

Step 1: Interpretation This relation helps determine system stability. \[ \therefore \text{Correct answer is (A)} \]