A conditionally stable system exhibits poor stability at

A conditionally stable system exhibits poor stability at :

A

Low frequencies

B

Reduced values of open loop gain

C

Increased values of open loop gain

D

High frequencies

A conditionally stable system is stable for the value of gain between two critical values. It is unstable if

A

The gain is increased beyond upper critical value

B

The gain is decreased below lower critical value

C

Both A and B

D

None of the above

The transfer function of a discrete time LTI system is given by
$$H\left( z \right) = {{2 - {3 \over 4}{z^{ - 1}}} \over {1 - {3 \over 4}{z^{ - 1}} + {1 \over 8}{z^{ - 2}}}}$$
Consider the following statements:
S₁ : The system is stable and causal for
$$ROC:\left| z \right| > {1 \over 2}$$
S₂ : The system is stable but not causal for
$$ROC:\left| z \right| S₃ : The system is neither stable nor causal for
$$ROC:{1 \over 4} Which one of the following statements is valid?

A

Both S₁ and S₂ are true

B

Both S₂ and S₃ true

C

Both S₁ and S₃ are true

D

S₁, S₂ and S₃ are all true

Consider the following statements with respect to the feedback of the control systems. i. Feedback can improve stability or be harmful to stability if it is not properly applied. ii. Feedback can always improve stability iii. In many situations the feedback can reduce the effect of noise and disturbance on system performance. iv. In general the sensitivity of the system gain of a feedback system of a parameter variation depends on where the parameter is located.

A

i, ii, iii and iv only

B

i, ii and iii only

C

i, iii and iv only

D

i, ii and iv only

Consider the following statements with respect to the feedback of the control systems: 1. Feedback can improve stability or be harmful to stability if it is not properly applied. 2. Feedback can always improve stability 3. In many situations the feedback can reduce the effect of noise and disturbance on system performance. 4. In general the sensitivity of the system gain of a feedback system of a parameter variation depends on where the parameter is located.

A

1,2 and 3 only

B

1,3 and 4 only

C

1,2 and 4 only

D

1,2,3 and 4 only

A network is said to be conditionally stable if:

A

│Гin│<1, │Гout│<1.

B

│Гin│>1, │Гout│>1

C

│Гin│>1, │Гout│<1

D

│Гin│<1, │Гout│>1

Let h(t) denote the impulse response of a causal system with transfer function $${1 \over {s + 1}}.$$ Consider the following three statements:
S₁ : The system is stable.
S₂ : $${{h\left( {t + 1} \right)} \over {h\left( t \right)}}$$ independent of t for t > 0.
S₃ : A non-causal system with the same transfer function is stable.
For the above system,

A

Only S₁ and S₂ are true

B

Only S₂ and S₃ are true

C

Only S₁ and S₃ are true

D

S₁, S₂ and S₃ are true

Statements : No gentleman is poor. All gentlemen are rich.

Conclusions :
I. No poor man is rich.
II. No rich man is poor.

A

Only conclusion I follows

B

Only conclusion II follows

C

Either I or II follows

D

Neither I nor II follows

E

Both I and II follow

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°

Assertion (A): The stability of the system is assured if the ROC includes the unit circle in z-plane. Reason (R): For a causal stable system all the poles should be outside the unit circle in the z-plane.

A

Both A and R are true and R is the correct explanation of A

B

Both A and R are true bit R is NOT the correct explanation of A

C

A is true but R is false

D

A is false but R is true

A conditionally stable system exhibits poor stability at

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