Free Process Control and Instrumentation MCQs with Answers
254 Process Control and Instrumentation MCQs from Chemical Engineering, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
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254 questions · page 12 of 13
- A. 63.2
- B. 87.5
- C. 95
- D. 100
Explanation: In controller response terminology, stabilising or settling time is conventionally specified as the time to reach about 95% of the final…
Correct answer: 95- A. Ultra pure metals
- B. Nickel-chromium alloys
- C. Iron-copper alloys
- D. Metal oxides
Explanation: Thermistors are temperature-sensitive semiconductor resistors commonly manufactured from sintered metal oxides such as oxides of…
Correct answer: Metal oxides- A. Global radiation
- B. Beam radiation
- C. Bright sunshine period
- D. None of these
Explanation: A pyranometer measures total or global solar radiation received on a surface, including both direct beam and diffuse sky radiation.
Correct answer: Global radiation- A. Kc(1 + TS)
- B. Kc[1 + (1/TS)]
- C. Kc/(1 + TS)
- D. Kc/[1 + (s/T)]
Explanation: A proportional plus reset controller combines proportional action with integral action, giving Gc(s)=Kc[1+1/(Ts)].
Correct answer: Kc[1 + (1/TS)]- A. Inside a pressure vessel
- B. Of an object without coming in contact with it
- C. Of liquid oxygen
- D. Of moving objects at high temperature
Explanation: Liquid oxygen is comparatively transparent to the radiation used by ordinary radiation thermometers, so the instrument may detect…
Correct answer: Of liquid oxygen- A. Iron-constantan
- B. Chromel-alumel
- C. Platinum-platinum/rhodium
- D. Copper-constantan
Explanation: Copper-constantan thermocouples have the narrowest useful range among these choices, typically extending only to roughly 350 to 400°C.
Correct answer: Copper-constantan- A. 961.93
- B. 630.74
- C. 1064.43
- D. 1261.93
Explanation: The antimony fixed point is 630.74°C, defined by equilibrium between solid and liquid antimony at standard atmospheric pressure.
Correct answer: 630.74- A. Combustion space in boilers
- B. Molten slag flowing out of blast furnace
- C. Hot blast (air) from stoves
- D. Rotary limestone calcination kiln
Explanation: A radiation or optical pyrometer requires sufficient emitted radiation from the target, whereas hot air is essentially non-luminous and…
Correct answer: Hot blast (air) from stoves- A. 100
- B. 250
- C. 350
- D. 750
Explanation: Mercury boils at about 357°C, so a mercury thermometer is commonly used up to approximately 350°C.
Correct answer: 350- A. > 100
- B. < 0
- C. 0-100
- D. > 50
Explanation: A constant-volume nitrogen thermometer uses the pressure of nitrogen as an indication of temperature and is suitable for temperatures…
Correct answer: > 100- A. 100
- B. 75
- C. 25
- D. 0
Explanation: An on-off controller has only two output states and changes state abruptly at the set point, corresponding to an ideal proportional…
Correct answer: 0- A. Point velocity
- B. Flow rate
- C. Vacuum
- D. Pressure
Explanation: A McLeod gauge measures very low absolute pressures, commonly expressed as vacuum in microns of mercury.
Correct answer: Vacuum- A. Polarimeter
- B. Polarograph
- C. Spectrometer
- D. Refractometer
Explanation: A refractometer determines composition or concentration from the refractive index, which changes with the angle of refraction.
Correct answer: Refractometer- A. Volumetric expansion
- B. Increase of thermal conductivity
- C. Increase of pressure
- D. Differential linear expansion
Explanation: Mercury expands appreciably and nearly uniformly in volume when heated, causing it to rise in the narrow thermometer capillary.
Correct answer: Volumetric expansion- A. 1/(1 + GH)
- B. G/(1 + GH)
- C. H/(1 + GH)
- D. G/(1 - GH)
Explanation: For a standard negative-feedback loop, the closed-loop transfer function is the forward-path gain divided by one plus the loop gain: C/R =…
Correct answer: G/(1 + GH)- A. 0.0001
- B. 0.001
- C. 0.01
- D. 0.1
Explanation: One micron of mercury is 0.001 mm Hg because the prefix micro means one-thousandth in this pressure convention.
Correct answer: 0.001237. The time constant of a first order process with resistance R and capacitance C is__________________?
- A. R + C
- B. R - C
- C. 1/RC
- D. RC
Explanation: A first-order system reaches about 63.2% of its final response after one time constant, and its resistance-capacitance model gives this…
Correct answer: RC- A. Both A. & B.
- B. An element which senses optical input and delivers thermal output
- C. Used for the measurement of thermal radiation
- D. Neither A. nor B.
Explanation: A bolometer detects radiant or optical energy through the heating it produces, so it is used for measuring thermal radiation and acts as…
Correct answer: Both A. & B.- A. Alumel
- B. Duralumin
- C. Constantan
- D. Rhodium
Explanation: Alumel, rhodium and constantan are used in thermocouple alloys or elements.
Correct answer: Duralumin- A. Voltage sensitive null
- B. None of these
- C. Current sensitive deflected
- D. Voltage sensitive deflected
Explanation: Dynamic strain measurement requires a deflection-type Wheatstone bridge, whose output voltage changes with strain and is measured…
Correct answer: Voltage sensitive deflected