All Free Chemical Engineering MCQs with Answers

• A. Copper-constantan
• B. Aluminium-Chromel
• C. Platinum-platinum + rhodium
• D. None of these

Explanation: A platinum-platinum/rhodium thermocouple, such as Type R or Type S, can measure temperatures around 1400°C.

• A. Is 30°
• B. Is 90° at the most
• C. Is 120°
• D. Approaches 180° asymptotically

Explanation: A second-order denominator contributes a phase lag that increases toward 180° as frequency becomes very large.

• A. Reproducibility
• B. Dead zone
• C. Static error
• D. Time lag

Explanation: Time lag delays an instrument's response to a changing input, making it a harmful dynamic characteristic.

• A. > 1.7 and > 30°
• B. 30°
• C. < 1.7 and 1.7 and < 30°

Explanation: Common control-system design targets require a gain margin greater than about 1.7 and a phase margin greater than 30° to provide adequate…

• A. Greater safety of operation
• B. All A., B. and C.
• C. Greater operation economy
• D. Better quality of product

Explanation: Plant instrumentation improves safety through monitoring and interlocks, product quality through tighter control, and operating economy by…

• A. Open
• B. Neither A. nor B.
• C. Either A. or B.
• D. Closed

Explanation: The Routh test examines the characteristic equation formed from the closed-loop denominator to determine pole stability.

• A. Convert the primary signal into a more useful quantity, usually an electric impulse
• B. Amplify the input signal
• C. Modify the input signal
• D. Codify/decodify the input signal

Explanation: A transducer converts a measured physical quantity or primary signal into another usable form, commonly an electrical signal for…

• A. -38.9
• B. -11.9
• C. -60.9
• D. -80.9

Explanation: Mercury freezes at approximately −38.9°C, so a mercury thermometer cannot provide a liquid-column reading below this temperature.

• A. 2.0
• B. 0.5
• C. 1.0
• D. 4.0

Explanation: Compare the denominator with s² + 2ζωₙs + ωₙ²: here ωₙ² = 4 gives ωₙ = 2, and 2ζωₙ = 2 gives ζ = 0.5. Thus the system is underdamped.

• A. Electrical conductivity
• B. Polarimetry
• C. Emission spectroscopy
• D. Dielectric constant end loss factor

Explanation: Water changes the dielectric constant and dielectric loss factor of an organic liquid substantially, allowing small amounts to be detected…

• A. Stefan Boltzmann law
• B. Kirchoff's law
• C. Wien's law
• D. Seebeck effect

Explanation: A radiation pyrometer determines temperature from the thermal radiation emitted by a hot body, commonly using the Stefan-Boltzmann…

• A. P-I controller
• B. P-controller
• C. P-D controller
• D. P-I-D controller

Explanation: A proportional controller alone leaves a steady-state error, called offset, and its offset is not removed by derivative action.

• A. Mcleod gauge
• B. Alphatron
• C. Bourdon gauge
• D. Ionisation gauge

Explanation: An ionisation gauge is designed for very low pressures in the micron and sub-micron range by measuring ions produced in the gas.

• A. Non-linear relation of emf to temperature
• B. Corrosion resistance
• C. Oxidation resistance
• D. Linear relation of emf to temperature

Explanation: A useful industrial thermocouple should give an emf that changes nearly linearly with temperature, while resisting oxidation and…

• A. Seebeck effect
• B. Peltier effect
• C. Joule heating effect
• D. Thomson effect

Explanation: The Peltier effect is the absorption or liberation of heat at a junction when current passes through it.

• A. Chromatograph
• B. Polarograph
• C. Polarimeter
• D. Spectrometer

Explanation: A polarimeter measures optical rotation by passing polarized light through a sample and determining the angle of rotation.

• A. Kc(1 + ηis + ηD ). s
• B. None of these
• C. Kc(1 + ηis + (1/ηD . s)
• D. Kc[1 + (1/ηis) + ηD . s)

Explanation: The ideal PID controller is written as Kc[1 + 1/(ηi s) + ηD s], combining proportional, integral, and derivative actions.

• A. Thermal conductivity cell
• B. X-ray diffraction
• C. Mass spectrometer
• D. Emission spectrometer

Explanation: A thermal conductivity cell compares the thermal conductivity of a gas sample with a reference gas, making it useful for continuous gas…

• A. Weight
• B. Stress
• C. Strain
• D. Velocity

Explanation: A load cell converts the force produced by a load into an electrical signal, so it is commonly used to measure weight.

• A. Teflon
• B. Asbestos
• C. Ceramic fibre
• D. Fibre glass

Explanation: Ceramic fibre withstands much higher temperatures than Teflon, asbestos, or fibreglass, so it provides the highest temperature rating…