GATE CH concept:transfer-functions PYQs & Answers

Questions 1–10 of 25. Imported answers require independent review unless marked reviewed.

A process exhibits an inverse response to a step input. Which of the following statements is/are necessarily TRUE about the process?

Your answerSelect all correct options. You can choose more than one.

Its transfer function has a positive zero.

Its transfer function has a negative zero.

The initial direction of the step response is opposite to the final steady state value.

The system is unstable due to a zero in the right half of the s-plane.

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Choose the transfer function that best fits the output response to a unit step input change shown in the figure

Diagram for Chemical Engineering question 25

Your answerChoose one option.

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Consider a process with transfer function

A first-order plus dead time (FOPDT) model is to be fitted to the unit step process reaction curve (PRC) by applying the maximum slope method.

Let

and

denote the time constant and dead time, respectively, of the fitted FOPDT model. The value of

is ____ (rounded off to 2 decimal places).

GIVEN: For

the unit step output response:

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For the block diagram shown in the figure, the correct expression for the transfer function

Diagram for Chemical Engineering question 48

Your answerChoose one option.

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A PD controller with transfer function

is used to stabilize an open-loop unstable process with transfer function

, where

and time is in minutes. From the necessary conditions for closed-loop stability, the maximum feasible value of

, in minutes, rounded off to 1 decimal place, is __________

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A liquid surge tank has

and

as the inlet and outlet flow rates respectively, as shown in the figure below.

is proportional to the square root of the liquid level

. The cross-sectional area of the tank is 20 cm². Density of the liquid is constant everywhere in the system. At steady state,

cm³s⁻¹ and

cm. The variation of

with

is approximated as a first order transfer function. Which one of the following is the CORRECT value of the time constant (in seconds) of this system?

Your answerChoose one option.

128

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A cascade control strategy is shown in the figure below. The transfer function between the output (

) and the secondary disturbance (

) is defined as

Which one of the following is the CORRECT expression for the transfer function

Diagram for Chemical Engineering question 44

Your answerChoose one option.

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Level (

) in a steam boiler is controlled by manipulating the flow rate (

) of the make-up (fresh) water using a proportional (P) controller. The transfer function between the output and the manipulated input is

. The measurement and valve transfer functions are both equal to 1. A process engineer wants to tune the controller so that the closed-loop response gives decaying oscillations under servo mode. Which one of the following is the CORRECT value of the controller gain to be used by the engineer?

Your answerChoose one option.

0.25

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The outlet concentration

of a plug flow reactor (PFR) is controlled by manipulating the inlet concentration

. The following transfer function describes the dynamics of this PFR.

In the above equation,

min

and

min

. The measurement and valve transfer functions are both equal to 1. The ultimate gain, defined as the proportional controller gain that produces sustained oscillations, for this system is _____ (rounded off to one decimal place).

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The transfer function of a measuring instrument is

At time

, a step change of +1 unit is introduced in the input of this instrument. The time taken by the instrument to show an increase of 1 unit in its output is _____ (rounded off to two decimal places).

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GATE CH concept:transfer-functions PYQs

How to practice concept:transfer-functions

Question 25

Question 25

Question 60

Question 48

Question 64

Question 25

Question 44

Question 45

Question 61

Question 62