All Free Chemical Engineering MCQs with Answers

• A. Electronic
• B. Pneumatic
• C. Hydraulic
• D. None of these

Explanation: A flapper-nozzle arrangement converts a mechanical displacement into a pneumatic pressure signal, forming the basic transmitter or…

• A. Dead zone
• B. Drift
• C. Static error
• D. None of these

Explanation: Static error is the difference between the true value and the value indicated by an instrument under steady conditions, so it directly…

• A. P
• B. PD
• C. PID
• D. PI

Explanation: A PI controller generally has the longest settling or stabilising time because integral action removes offset but can make the response…

• A. Optical pyrometer
• B. Mercury in glass thermometer
• C. Iron-constantan thermocouple
• D. Alcohol filled thermometer

Explanation: An optical pyrometer estimates temperature from thermal radiation and is generally less accurate than direct-contact thermometers over…

• A. High drift
• B. High fidelity
• C. High measuring lag
• D. Poor reproducibility

Explanation: High fidelity means an instrument reproduces the input signal accurately in magnitude and form, making it a desirable characteristic.

• A. Under damped
• B. None of the above
• C. Over damped
• D. Critically damped

Explanation: Two identical non-interacting tanks in series give a denominator proportional to (τs + 1)², which has two equal real poles.

• A. 1/(s2 + 2)
• B. 1/(s2 - 2s + 3)
• C. 1/(s2 + 2s + 2)
• D. exp (-20s)/(s2 + 2s - 1)

Explanation: A system is stable when all poles lie in the left half of the s-plane. For option c, s² + 2s + 2 = 0 gives poles -1 ± j, whereas the other…

• A. Determining water purity
• B. Solids and metal analysis
• C. Determination of CO2 in gases
• D. NOx determination

Explanation: Emission spectroscopy identifies elements from the characteristic wavelengths emitted by excited atoms, so it is widely used for elemental…

• A. 800
• B. 400
• C. 1200
• D. 1500

Explanation: Optical radiation pyrometers are used for high-temperature measurement and typically begin operating at about 800°C.

• A. Gage as well as vacuum
• B. Absolute as well as differential
• C. Neither A. nor B.
• D. Both A. and B.

Explanation: Strain-gage transducers can be arranged to measure gauge, vacuum, absolute, or differential pressure, depending on their reference and…

• A. -1
• B. 0
• C. 1
• D. ∞

Explanation: A pole is a value of s at which the transfer function becomes unbounded, so G(s) approaches infinity.

• A. Gauge
• B. Atmospheric
• C. Vacuum
• D. Absolute

Explanation: A mercury barometer balances atmospheric pressure against the pressure exerted by the mercury column.

• A. Depends only upon the open loop transfer function
• B. Determines its stability
• C. All A , B & C.
• D. Is the same for set point or load changes

Explanation: The characteristic equation comes from the denominator of the closed-loop transfer function, and its roots determine stability.

• A. Impulse
• B. Unit step
• C. None of these
• D. Frequency

Explanation: A sinusoidal input is used to determine a system's frequency response, which describes the steady-state gain and phase at different…

• A. Elimination of offset
• B. Reduction of offset
• C. Reduction of stability time
• D. None of these

Explanation: Proportional control alone usually leaves a steady-state offset after a load change.

• A. Roots of the characteristic equation should be real
• B. Poles of the closed loop transfer function should lie in the left half of the complex plane
• C. Bode plots of the corresponding open loop transfer function should monotonically decrease
• D. Poles of the closed loop transfer function should lie in the right half of the complex plane

Explanation: A continuous-time linear feedback system is stable when all closed-loop poles lie in the left half of the s-plane.

• A. Insulator
• B. Conductor
• C. Solid semi-conductor
• D. Liquid semi-conductor

Explanation: A thermistor is made from semiconductor materials whose electrical resistance changes strongly with temperature.

• A. Voltage measuring
• B. Temperature measuring
• C. Temperature compensating
• D. Both B. & C.

Explanation: Thermistors are commonly used to measure temperature and to compensate for temperature-dependent changes in circuits.

• A. Pointer
• B. Bourdon tube
• C. Bulb
• D. None of these

Explanation: The bulb senses temperature and is the primary element, while the Bourdon tube responds to the resulting vapour pressure and acts as the…

• A. Mercury in glass thermometer
• B. Filled system thermometer
• C. Radiation/infrared pyrometer
• D. Thermo electric pyrometer

Explanation: A radiation or infrared pyrometer detects thermal radiation emitted by the object, so it can measure temperature without physical contact.