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According to Bode stability criterian, a system is unstable, if the open loop frequency response exhibits an amplitude ratio exceeding unity at frequency for which phase lag is
A
0°
B
45°
C
90°
D
180°
Correct Answer:
180°
A control system is unstable, if the open loop frequency response exhibits an amplitude ratio exceeding unity at the crossover frequency. This is __________ criterion.
A
Bode stability
B
Nyquist
C
Routh stability
D
None of these
Assertion (A): The closed loop stability can be determined from the poles of an open loop system and the polar plot of the frequency response. Reason (R): Unstable system has right half poles.
A
Both A and R are true and R is correct explanation of A
B
Both A and R are true and R is not correct Explanation of A
C
A is True and R is false
D
A is False and R is true
Assertion (A): Relative stability of the system reduces due to the presence of transportation lag. Reason (R): Transportation lag can be conveniently handled by Bode plot.
A
Both A and R are true but R is correct explanation of A
B
Both A and R are true but R is correct explanation of A
C
A is true but R is false
D
A is false but R is true
A certain inverting amplifier has a closed-loop voltage gain of 25. The OP-amp has an open-loop voltage gain of 100,000. If an OP-amp with an open-loop voltage gain of 200,000 is substituted in the arrangement, the closed-loop gain
A
doubles
B
drops to 12.5
C
remains at 25
D
increases slightly
A minimum phase unity feedback system has a bode plot with a constant slope of -20dB/decade for all frequencies. What is the value of the maximum phase margins of the system?
A
0°
B
90°
C
-90°
D
180°
The open-loop transfer function of a unity feedback system is K/(s^2 (s+5))The system is unstable for
A
K>5
B
K<5
C
K>0
D
All of the mentioned
Consider the following statements: Nichol’s chart gives information about. i. Closed loop frequency response. ii. The value of the peak magnitude of the closed loop frequency response Mp. iii. The frequency at which Mp occurs. Which of the above statements are correct?
A
2 and 3
B
1 and 2
C
1 and 3
D
1,2 and 3
The open loop transfer functions with unity feedback are given below for different systems. Among these systems the unstable system is
A
G(s) =2/s+2
B
G(s) =2/s(s+2)
C
G(s) =2/(s+2)s^2
D
G(s) =2(s+1)/s(s+2)
Consider a conducting loop of radius a and total loop resistance R placed in a region with a magnetic field B thereby enclosing a flux $${\phi _0}$$ . The loop is connected to an electronic circuit as shown, the capacitor being initially uncharged.
If the loop is pulled out of the region of the magnetic field at a constant speed u, the final output voltage V
out
is independent of
A
$${\phi _0}$$
B
u
C
R
D
C
The open loop control transfer function of a unity feedback system is given by : G(s) =K/(s+2)(s+4)(s^2+6s+25) Which is the value of K which causes sustained oscillations in the closed loop system?
A
590
B
790
C
990
D
1190
