BE/B Eng Bachelor of Engineering Bachelor of Engineering Science 5 — Questions and Answers
Question 1: Which failure theory is most appropriate for predicting yielding in ductile metals under multiaxial stress?
- Maximum normal stress theory
- Maximum shear stress (Tresca) theory (Correct answer)
- Mohr's rupture theory
- Maximum strain theory
Correct answer: Maximum shear stress (Tresca) theory
The Tresca (maximum shear stress) theory and von Mises theory are both well-suited for ductile metals; Tresca is more conservative and widely used in pressure vessel design.
Question 2: What is the primary advantage of using a PID controller over a proportional-only controller?
- Faster response to disturbances
- Elimination of steady-state error (Correct answer)
- Simpler tuning procedure
- Reduced overshoot in all cases
Correct answer: Elimination of steady-state error
The integral term in a PID controller accumulates error over time, driving steady-state error to zero for step inputs, which a proportional-only controller cannot achieve.
Question 3: In chemical engineering, what does the term 'selectivity' refer to in a chemical reactor?
- The fraction of feed converted to any product
- The ratio of desired product formed to undesired product formed (Correct answer)
- The speed at which the reaction reaches equilibrium
- The temperature sensitivity of the reaction rate
Correct answer: The ratio of desired product formed to undesired product formed
Selectivity measures how much of the reacted feed goes to the desired product versus unwanted byproducts, distinguishing it from conversion which only measures reactant consumption.
Question 4: In surveying, the term 'benchmark' refers to:
- A standard performance measure for instruments
- A reference point of known elevation used in leveling surveys (Correct answer)
- The midpoint of a survey traverse
- A horizontal control point with known coordinates
Correct answer: A reference point of known elevation used in leveling surveys
A benchmark is a fixed reference point with a precisely known elevation used as a starting datum for differential leveling surveys.
Question 5: Which signal type has a continuous range of values and is defined at every instant in time?
- Digital signal
- Discrete-time signal
- Analog signal (Correct answer)
- Quantized signal
Correct answer: Analog signal
An analog signal is continuous in both time and amplitude, whereas digital signals are discrete in both dimensions.
Question 6: In environmental engineering, BOD (Biochemical Oxygen Demand) measures:
- The total dissolved oxygen in water
- The oxygen required by microorganisms to decompose organic matter (Correct answer)
- The concentration of nitrogen compounds in wastewater
- The chemical oxygen demand of inorganic pollutants
Correct answer: The oxygen required by microorganisms to decompose organic matter
BOD is the amount of dissolved oxygen consumed by biological organisms when decomposing organic matter in water at a given temperature over a specific time period (typically 5 days at 20°C).
Question 7: Fourier's law of heat conduction states that heat flux q is proportional to:
- Temperature squared
- The negative temperature gradient (Correct answer)
- The absolute temperature
- Rate of temperature change with time
Correct answer: The negative temperature gradient
Fourier's law states q = −k(dT/dx), where heat flows from hot to cold regions proportional to the negative temperature gradient and thermal conductivity k.
BE/B Eng Bachelor of Engineering Bachelor of Engineering Science 5
Which failure theory is most appropriate for predicting yielding in ductile metals under multiaxial stress?