For a stable system having two or more gain crossover frequencies the phase margin is measured at the highest crossover frequency.

Which of the following statements are correct? 1. A lowpass filter passes low frequencies and stops high frequencies. 2. A highpass filter passes high frequencies and rejects low frequencies 3. A bandpass filter passes frequencies within a frequency band and attenuates frequencies outside the band. 4. A bandstop filter passes frequencies within the band and blocks/attenuates frequencies outside a frequency band.

A

1, 2 and 4 only

B

1, 3 and 4 only

C

2, 3 and 4 only

D

1, 2 and 3 only

The network formed by resistors and capacitors for modifying the rate of change of gain and the phase shift is called a compensating network. Which of the following statements are not correct ? (A) The main purpose of a compensating network is to modify the performance of op-amp ciruit over the desired frequency range (B) There are two types of op-amps : internally compensated and externally compensated (C) 741 C is an externally compensated op-amp while 709 C is internally compensated op-amp (D) The phase lag and phase lead are most commonly used compensating networks in op-amps (E) Phase lag contributes a positive phase angle and phase lead a negative phase angle Choose the most appropriate answer from the options given below :

A

(B) and (C) only

B

(B) and (E) only

C

(C) and (D) only

D

(C) and (E) only

Seven people A, B, C, D, E, F and G live on separate floors of a 7-floor building. Ground floor is numbered 1, first floor is numbered. 2 and so on until the topmost floor is numbered 7. Each one of these having a different cars-Cadillac, Ambassador, Fiat, Maruti, Mercedes, Bedford and Fargo but not necessarily in the same order. Only three people live above the floor on which A lives. Only one person lives between A and the one having a car Cadillac. F lives immediately below the one having a car Bedford. The one having a car Bedford lives on an even-numbered floor. Only three people live between the ones having a car Cadillac and Maruti. E lives immediately above C. E is not having a car Maruti. Only two people live between B and the one having a car Fargo. The one having a car Fargo lives below the floor on which B lives. The one having a car Fiat does not live immediately above D or immediately below B. D does not live immediately above or immediately below A. G does not have a car Ambassador. Question : How many people live between the floors on which D and the one having a car Bedford ?

A

One

B

Two

C

Three

D

Four

For a stable closed loop system, the gain at phase crossover frequency should always be:

A

< 20 dB

B

< 6 dB

C

> 6 dB

D

> 0 dB

Assertion (A): The phase angle plot in Bode diagram is not affected by the variation in the gain of the system. Reason(R): The variation in the gain of the system has no effect on the phase margin of the system.

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

Which of the following statements is/are correct with respect to a Scott-connected transformer? I. It can do 3-phase to 2-phase conversion II. It can do 2-phase to 3-phase conversion III. It can do 2-phase to 4-phase conversion IV. It can do 3-phase to 4-phase conversion

A

Statements IV and II

B

Statement II only

C

Statements III and IV

D

Statements I and II

Which one of the following statements is correct for gain margin and phase margin of two closed-loop systems having loop functions G(s) H(s) and exp(-s) G(s) H(s)?

A

Both gain and phase margins of the two systems will be identical

B

Both gain and phase margins of G(s) H(s) will be more

C

Gain margins of the two systems are the same but phase margins of G(s) H(s) will be more

D

Phase margins of the two systems are the same but gain margin of G(s) H(s) will be less

Which of the following analysis is more convenient to see the effect of additional zero and pole in the system on the phase margin and the gain margin?

A

Root locus

B

Nyquist plot

C

Bode plot

D

Routh-Hurwitz criterion

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

The critical value of gain for the system is 40. The system is operating at a gain of 20. The gain margin of the system is :

A

2 dB

B

3 dB

C

6 dB

D

4 dB

For a stable system having two or more gain crossover frequencies the phase margin is measured at the highest crossover frequency.

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