All Free Chemical Engineering MCQs with Answers

• A. Amplitude ratio
• B. Gain in P controller
• C. Reciprocal of amplitude ratio
• D. Gain in P-I controller

Explanation: At the phase-crossover frequency, gain margin is the factor by which the loop gain can increase before reaching the stability limit.

• A. Thermocouple
• B. Radiation pyrometer
• C. Bimetallic thermometer
• D. Mercury thermometer

Explanation: A mercury thermometer can show a pronounced dip or reversal in indication because mercury and the glass bulb respond with different…

• A. 800-1600
• B. 400-1600
• C. 800-2500
• D. 400-1000

Explanation: Photoelectric pyrometers are non-contact instruments commonly used for high-temperature measurement, with a typical range of about 800 to…

• A. Load
• B. Controlled
• C. Manipulated
• D. None of these

Explanation: The outlet temperature is the process quantity whose value is measured and maintained by the controller, so it is the controlled variable.

• A. Hydrometer
• B. Contact-type electric indicators
• C. Both A. and C.
• D. Displacement meter

Explanation: A hydrometer determines specific gravity from buoyancy, while a displacement meter can provide an in-line continuous indication based on…

• A. Proportional integral-derivative (PID) controller
• B. Proportional-derivative (PD) controller
• C. Proportional-integral (PI) controller
• D. Proportional controller

Explanation: Integral action removes steady-state offset, while derivative action improves damping and reduces oscillation.

• A. Ratio
• B. Product
• C. Sum
• D. Difference

Explanation: For non-interacting elements connected in series, the output of one becomes the input to the next, so their transfer functions multiply.

• A. - 273° & 80°
• B. 32° & 460°
• C. 0° & 80°
• D. 32° & 80°

Explanation: The Réaumur scale assigns 0°Ré to the ice point and 80°Ré to the steam point, because the interval between these fixed points is divided…

• A. Teflon
• B. Thick paper
• C. Bakelite
• D. Synthetic rubber

Explanation: Synthetic rubber is flexible and can deflect under pressure, making it suitable for non-metallic diaphragms.

• A. Decay ratio = (overshoot)2
• B. Decay ratio = overshoot
• C. Overshoot increases for increasing damping co-efficient
• D. Large damping co-efficient means smaller damping

Explanation: For an underdamped second-order system, successive peak amplitudes have a decay ratio equal to exp[-2πζ/√(1−ζ²)], while the fractional…

• A. Thermocouples
• B. Bimetallic thermometers
• C. Thermostats
• D. Relays for opening & closing of electrical circuits

Explanation: A thermocouple generates voltage from the junction of two dissimilar metals and does not use a mechanically deflecting bimetal strip.

• A. Orsat apparatus
• B. Thermal conductivity cell
• C. Zirconia probe
• D. Chromatograph

Explanation: A thermal-conductivity cell can be used in continuous gas analysis because the mixture's thermal conductivity changes with composition.

• A. - 39 and 350
• B. - 51 and 439
• C. - 79 and 395
• D. - 10 and 425

Explanation: Mercury freezes at about −38.8°C and boils at about 356.7°C, conventionally rounded here to −39°C and 350°C.

• A. None of these
• B. Which exhibits an unbounded response to a bounded input
• C. Which satisfies the conditions for a servo problem
• D. For which the output response is bounded for all bounded input

Explanation: A stable system has a bounded output whenever the input remains bounded, which is the bounded-input bounded-output criterion.

• A. Cannot be used to test the stability of a control system containing transportation lag
• B. Criterion provides information about the actual location of roots
• C. Criterion is not applicable to systems with polynomial characteristic equation
• D. Cannot determine as to how many roots of the characteristics equation have positive real roots

Explanation: The Routh test applies to polynomial characteristic equations and determines how many roots lie in the right half-plane, but not their…

• A. > 2 (gauge)
• B. < atmospheric
• C. 10 (absolute)

Explanation: Bourdon gauges are mechanical pressure instruments generally used for positive, moderate-to-high gauge pressures, commonly above about 2…

• A. Has a slower speed of response
• B. Can't measure the temperature of moving objects
• C. Can measure higher temperature
• D. Is more affected by corrosive atmosphere

Explanation: Radiation pyrometers measure emitted radiation without contacting the object, so they are suitable for temperatures beyond the practical…

• A. First order system
• B. Second order system (overdamped)
• C. Second order system (underdamped)
• D. Multiple first order system

Explanation: The thermal well and the thermocouple each contribute a thermal time constant, so the combined response is modeled as a cascade of…

• A. Routh test
• B. Frequency response methods
• C. Root locus methods
• D. None of these

Explanation: Transportation lag produces an exponential delay term and is most conveniently assessed through its frequency response, where the delay…

• A. Enhancement or attenuation of radiation occurs in the sighting path
• B. Object has varying emissivity
• C. Object and surrounding are at almost the same temperature
• D. Object is transparent

Explanation: Radiation pyrometer readings are affected by emissivity, sight-path absorption, transparency, and reflected surroundings.