All Free Chemical Engineering MCQs with Answers

• A. -1, -4
• B. 1, 4
• C. 2, 3
• D. -2, -3

Explanation: The poles are the roots of the denominator of the open-loop transfer function, so s = -2 and -3.

• A. Load
• B. Set point
• C. Both A. & B.
• D. Neither A. nor B.

Explanation: A feed-forward controller measures a load disturbance and compensates before it affects the process output.

• A. Reduce measuring lag
• B. Guard against corrosive and oxidising action on thermocouple materials
• C. Increase the fidelity
• D. Increase the sensitivity

Explanation: A thermal well places a protective barrier between the temperature sensor and the process fluid, guarding it against corrosion, oxidation…

• A. 45°
• B. -90°
• C. -180°
• D. -45°

Explanation: For a first-order system, the phase angle is -tan⁻¹(ωτ). Here ωτ = 1 × 1 = 1, giving a phase shift of -tan⁻¹(1) = -45°.

• A. Mercury thermometer
• B. None of these
• C. Radiation pyrometer
• D. Bimetallic thermometer

Explanation: A bimetallic thermometer is suitable for approximately -40 to 425°C and is mechanically simple for moderate temperature measurement.

• A. 0.1
• B. 3
• C. 13
• D. 29

Explanation: The platinum-rhodium thermocouple composition commonly listed in this classification is platinum with about 13% rhodium, corresponding to…

• A. Feed forward control
• B. More than one feed-back loop
• C. On-off control
• D. One feed-back loop

Explanation: Cascade control uses a primary feedback loop whose controller sets the target for a secondary feedback loop.

• A. Iron-constantan
• B. Chromel-alumel
• C. Platinum-platinum/rhodium
• D. Copper-constantan

Explanation: The platinum-platinum/rhodium thermocouple withstands the highest temperatures among these choices, making it suitable for…

• A. Linear
• B. Square root
• C. Exponential
• D. Parabolic

Explanation: The emf produced by a thermocouple is nonlinear with temperature and is commonly represented by a polynomial, approximately parabolic over…

• A. Tubular reactor
• B. CSTR
• C. On-off controller
• D. None of these

Explanation: A tubular reactor is a distributed-parameter system because concentration and temperature vary continuously along its length.

• A. Bubbler system
• B. Differential pressure manometer
• C. Diaphragm box system
• D. Air-trap system

Explanation: A differential-pressure manometer measures the pressure difference between the liquid side and the reference side; this difference is…

• A. Steel
• B. Nichrome
• C. Vycor (a glass)
• D. Inconel

Explanation: Vycor has a thin, low-thermal-mass construction and gives a faster thermocouple response than the heavier metallic protection wells…

• A. Increases
• B. Decreases
• C. Remain constant
• D. Increases exponentially

Explanation: Platinum has a positive temperature coefficient of resistance, so its resistance increases as temperature rises.

• A. Platinum resistance thermometer
• B. Thermocouple
• C. Optical pyrometer
• D. Bimetallic thermometer

Explanation: An optical pyrometer measures the radiation emitted by a hot surface without contacting it, making it suitable for a red-hot furnace.

• A. Phosphor bronze
• B. Monel metal
• C. Stainless steel
• D. Cast iron

Explanation: Bourdon tubes require elastic, corrosion-resistant metals such as phosphor bronze, Monel, or stainless steel.

• A. Strip
• B. Diaphragm
• C. Bellow
• D. Bourdon tube

Explanation: Elastic pressure gauges commonly use Bourdon tubes, bellows, or diaphragms, whose deformation indicates pressure.

• A. Radiation pyrometer
• B. platinum-platinum/rhodium thermocouple
• C. Iron-constantan thermocouple
• D. Platinum resistance thermometer

Explanation: The dome of a blast-furnace stove reaches very high temperatures, for which a platinum-platinum/rhodium thermocouple is suitable and…

• A. Heat content of the system
• B. Liquid volume in the tank
• C. Level of liquid
• D. Flow rate

Explanation: In the hydraulic analogy, liquid level is the potential difference or voltage, while flow rate corresponds to current.

• A. Unstable
• B. Stable
• C. Critically damped
• D. None of these

Explanation: A negative gain margin means the loop would need a reduction in gain to reach the stability limit, indicating that the present closed-loop…

• A. R/TS
• B. R/(TS + 1)
• C. 1/TS
• D. None of these

Explanation: For a single tank, the level response to inlet flow is a first-order system: H(s)/Q(s) = R/(τs + 1), where τ is the time constant.