Question

Consider a feedback system with gain margin of about 30. At what point does the Nyquist plot cross the negative real axis?

• A. -3
• B. -0.3
• C. -30
• D. -0.03

Hint:

The gain margin in a feedback system is related to the frequency at which the Nyquist plot crosses the negative real axis.

Answer 1

The Correct Option is B

In a Nyquist plot for a feedback system, the gain margin is defined as the amount of gain change required to make the open-loop transfer function equal to -1. A gain margin of 30 means the Nyquist plot crosses the negative real axis at -0.3. Thus, the correct answer is -0.3.