Multiple Choice Questions and Answers (MCQ) on Chemical Engineering Process Control and Instrumentation
01. When a bare thermocouple is covered by a protective sheath, the response becomes
(A) Faster and oscillatory
(B) Faster and non-oscillatory
(C) Slower and oscillatory
(D) Slower and non-oscillatory
Answer: Option D
02. Which of the following thermocouples is incapable of measuring sub-zero (i.e., < 0°C) temperature?
(A) Chromel-alumel
(B) Iron-constantan
(C) Platinum-platinum + rhodium
(D) Copper-constantan
Answer: Option C
03. __________ temperature scale assigns 0° to the ‘ice point’ and 80° to the ‘steam point’.
(A) Celsius
(B) Rankine
(C) Reaumur
(D) Fahrenheit
Answer: Option C
04. “An emf of the order of mV is generated when two solutions of different hydrogen ion concentration are separated by a thin glass wall”. This is the working principle of a
(A) pH meter
(B) Polarimeter
(C) Chromatograph
(D) Polarograph
Answer: Option A
05. The transfer function of a process is 1/(16s2 + 8s + 4). If a step change is introduced into the system, then the response will be
(A) Under damped
(B) Critically damped
(C) Over damped
(D) None of these
Answer: Option A
06. A control system has the following transfer function
F(s) = [(s – 1)(s + 1)]/[s (s – 2)(s + 4)]
The initial value of the corresponding time function is
(A) 1
(B) 1/8
(C) 7/8
(D) -1
Answer: Option A
07. Bode diagram is a plot of
(A) log (AR) vs. log (f) and (φ) vs. log (f)
(B) log (AR) vs. f and log φ vs. f
(C) AR vs. log (f) and φ vs. log (f)
(D) None of these
Answer: Option A
08. Block diagram of a simple standard control system is shown below in the figure. Which of the following statement about the above control system is wrong?
(A) The transfer functions of the measuring element and the process is represent by H and G2 respectively
(B) The overall transfer function for the change in load (X = 0) is given by Y/X1 = (Gc . G1 . G2)/(1 + Gc . G1 . G2 . H)
(C) The overall transfer function for the change in set point (X1 = 0) is given by Y/X = (Gc . G1 . G2)/(1 + Gc . G1 . G2 . H)
(D) Manipulated variable is represented by C
Answer: Option D
09. A bolometer is
(A) Used for the measurement of thermal radiation
(B) An element which senses optical input and delivers thermal output
(C) Both (A) & (B)
(D) Neither (A) nor (B)
Answer: Option C
10. The frequency at which maximum amplitude ratio is attained is called the __________ frequency.
(A) Corner
(B) Resonant
(C) Cross-over
(D) Natural
Answer: Option B
11. The time constant of a first order process with resistance R and capacitance C is
(A) R + C
(B) R – C
(C) RC
(D) 1/RC
Answer: Option C
12. Thermocouple is suitable for measuring
(A) Liquid temperatures only
(B) Very high temperatures only
(C) Very low temperatures only
(D) Both high and low temperatures
Answer: Option D
13. Very low pressure is expressed in microns (μ), which is equal to __________ mm of Hg column (absolute) at 0°C.
(A) 0.0001
(B) 0.001
(C) 0.01
(D) 0.1
Answer: Option B
14. For the time domain function f(t) = t, the Laplace transform of ∫0t f(t) dt is given by
(A) 1/2 S3
(B) 2/S3
(C) 1/S3
(D) 2/S2
Answer: Option C
15. What is the overall transfer function (C/R) of the following block diagram if G = G1. G2. G3 and H = H1.H2.
(A) 1/(1 + GH)
(B) G/(1 + GH)
(C) H/(1 + GH)
(D) G/(1 – GH)
Answer: Option B
16. Phase margin is equal to
(A) 180° – phase lag
(B) Phase lag – 180°
(C) Phase lag + 180°
(D) Phase lag + 90°
Answer: Option A
17. Working principle of mercury in glass thermometer is based on the __________ of mercury with increase in temperature.
(A) Increase of pressure
(B) Increase of thermal conductivity
(C) Volumetric expansion
(D) Differential linear expansion
Answer: Option C
18. Coming soon.
19. Continuous flue gas analyser makes use of paramagnetic properties of some of its constituents, which move towards the strongest part of the magnetic field thus displacing diamagnetic gases. Which of the following gases is diamagnetic?
(A) CO2
(B) O2
(C) NO
(D) NO2
Answer: Option A
20. Change of angle of refraction with composition comprises the working principle of a
(A) Polarimeter
(B) Polarograph
(C) Spectrometer
(D) Refractometer
Answer: Option D
21. A non-linear chemical system is exemplified by a/an
(A) Isothermal CSTR
(B) Mixer
(C) Non-isothermal CSTR
(D) None of these
Answer: Option C
22. Mcleod gauge is used to measure the
(A) Point velocity
(B) Flow rate
(C) Vacuum
(D) Pressure
Answer: Option C
23. All the thermocouples used for temperature measurement use dissimilar metal
(A) Strips
(B) Bars
(C) Wires
(D) Beads
Answer: Option C
24. Find the Laplace transform of the following input function shown in figure.
(A) (1 – e-s)/[S (1 – e-2s)]
(B) 2(1 – e-s)/S
(C) (1 – e-s)/[S (1 + e-s)]
(D) e-s (1 – e-s)/[S (1 + e-2s)]
Answer: Option A
25. Dead zone is the
(A) Same as time constant
(B) Same as transportation lag
(C) Maximum change in the variable that does not change the reading of the instrument
(D) None of these
Answer: Option C