Thermodynamics MCQ Set 3

THERMODYNAMICS MCQ SET 1

Q1. A perfect gas obeys the equation:

A) PV = RT
B) PV = nRT
C) PV = mRT
D) P = RT

Show Answer

Answer: C) PV = mRT
Explanation: For a perfect gas, PV = mRT, where m = mass, R = gas constant.

Q2. In a throttling process:

A) Enthalpy remains constant
B) Pressure remains constant
C) Volume remains constant
D) Temperature remains constant

Show Answer

Answer: A) Enthalpy remains constant
Explanation: Throttling is an isenthalpic process.

Q3. The third law of thermodynamics states that:

A) Entropy becomes zero at absolute zero
B) Energy is conserved
C) Entropy remains constant
D) Heat is work

Show Answer

Answer: A) Entropy becomes zero at absolute zero
Explanation: As temperature approaches zero, entropy tends to zero.

Q4. The relation between Cp, Cv, and R is:

A) Cp = Cv + R
B) Cp = Cv – R
C) Cp = R – Cv
D) Cp = Cv × R

Show AnswerAnswer: A) Cp = Cv + R
Explanation: This relation applies for an ideal gas.

Q5. The specific heat of water is approximately:

A) 1 kJ/kg·K
B) 4.18 kJ/kg·K
C) 2.1 kJ/kg·K
D) 0.5 kJ/kg·K

Show Answer

Answer: B) 4.18 kJ/kg·K
Explanation: Water has high specific heat capacity, useful in cooling systems.

Q6. The property of a system which depends only on its state and not on the path followed is called:

A) Path function
B) Point function
C) Process function
D) Flow function

Show Answer

Answer: B) Point function
Explanation: Properties like pressure, volume, and temperature depend only on the system’s state, not on the process path.

Q7. Enthalpy is defined as:

A) H = U + PV
B) H = U – PV
C) H = U/PV
D) H = PV – U

Show Answer

Answer: A) H = U + PV
Explanation: Enthalpy represents total heat content of the system, including internal energy and flow work.

Q8. The SI unit of heat is:

A) Calorie
B) Joule
C) Watt
D) Erg

Show Answer

Answer: B) Joule
Explanation: Joule is the standard SI unit of energy and heat.

Q9. A cyclic process is one in which:

A) Initial and final states are same
B) Pressure remains constant
C) Volume remains constant
D) Temperature remains constant

Show Answer

Answer: A) Initial and final states are same
Explanation: In a cyclic process, the system returns to its original state.

Q10. The efficiency of a heat engine can never be:

A) 100%
B) 75%
C) 50%
D) 25%

Show Answer

Answer: A) 100%
Explanation: Due to the second law of thermodynamics, no engine can convert all heat into work.