Question:

If the Nyquist plot encircles the point \((-1,0)\) twice in the clockwise direction and the open-loop system has one RHP pole, then the number of closed-loop RHP poles is

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Nyquist stability criterion: \[ \boxed{ Z=P-N } \] where \[ \begin{aligned} P&=\text{Open-loop RHP poles}, N&=\text{Clockwise encirclements of }(-1,0), Z&=\text{Closed-loop RHP poles}. \end{aligned} \]
Updated On: Jul 14, 2026
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The Correct Option is D

Solution and Explanation

Step 1: Apply the Nyquist stability criterion. According to the Nyquist criterion, \[ Z=P-N, \] where \[ \begin{aligned} P &= \text{Number of open-loop RHP poles}, N &= \text{Net clockwise encirclements of }(-1,0), Z &= \text{Number of closed-loop RHP poles}. \end{aligned} \]

Step 2:
Substitute the given values. Given, \[ P=1, \] and the Nyquist plot encircles \((-1,0)\) twice clockwise, so \[ N=-2. \] Therefore, \[ Z=P-N =1-(-2) =3. \] Hence, \[ \boxed{Z=3.} \] Therefore, \[ \boxed{(D)} \] is the correct answer.
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