Fundamentals of Engineering Basic 4 — Questions and Answers
Question 1: Which thermodynamic law states that energy cannot be created or destroyed?
- First Law (Correct answer)
- Second Law
- Third Law
- Zeroth Law
Correct answer: First Law
The First Law of Thermodynamics is the law of conservation of energy.
Question 2: What is the efficiency of a heat engine that absorbs 1000 J and rejects 600 J?
- 40% (Correct answer)
- 60%
- 16.7%
- 167%
Correct answer: 40%
Efficiency η = (Q_H − Q_C) / Q_H = (1000 − 600) / 1000 = 0.40 = 40%.
Question 3: Which process occurs at constant pressure?
- Isobaric (Correct answer)
- Isothermal
- Isochoric
- Adiabatic
Correct answer: Isobaric
An isobaric process occurs at constant pressure, while the other terms describe constant temperature, constant volume, and no heat transfer respectively.
Question 4: The ideal gas law is best expressed as:
- PV = nRT (Correct answer)
- PV = mRT
- P = ρRT
- PV = NkT only
Correct answer: PV = nRT
The ideal gas law PV = nRT relates pressure, volume, moles, and temperature using the universal gas constant R.
Question 5: Entropy is a measure of:
- Disorder or randomness of a system (Correct answer)
- Total energy of a system
- Heat transferred at constant pressure
- Enthalpy change of a reaction
Correct answer: Disorder or randomness of a system
Entropy quantifies the degree of disorder or the number of possible microscopic configurations of a thermodynamic system.
Question 6: Which heat transfer mode requires a medium (fluid or solid) and involves bulk movement?
- Convection (Correct answer)
- Conduction
- Radiation
- Evaporation
Correct answer: Convection
Convection transfers heat through the bulk motion of a fluid, unlike conduction (direct contact) or radiation (electromagnetic waves).
Question 7: A Carnot engine operates between 800 K and 400 K. What is its maximum theoretical efficiency?
- 50% (Correct answer)
- 25%
- 75%
- 100%
Correct answer: 50%
Carnot efficiency = 1 − T_L/T_H = 1 − 400/800 = 0.50 = 50%.
Fundamentals of Engineering Basic 4
Which thermodynamic law states that energy cannot be created or destroyed?