Chapter-11 Thermodynamics — Online MCQ Test
PHYSICS · Grade 11 · CBSE(NCERT)
Practice Chapter-11 Thermodynamics with a free chapter-wise online MCQ test.
This chapter covers: Thermal equilibrium - Zeroth law of thermodynamics - Internal energy - First law of thermodynamics - Isothermal process - Adiabatic process - Isobaric process - Isochoric process -....
AI-generated questions from basic to board-exam level, with instant results and explanations.
Chapter-11 Thermodynamics — Important Questions & Answers
What does the Zeroth Law of Thermodynamics state?
- A. Energy cannot be created or destroyed
- B. If two systems are in thermal equilibrium with a third system, they are in thermal equilibrium with each other
- C. The entropy of an isolated system always increases
- D. Heat always flows from hot to cold bodies
Answer: B. If two systems are in thermal equilibrium with a third system, they are in thermal equilibrium with each other
The Zeroth Law defines thermal equilibrium and provides the basis for temperature measurement by establishing transitivity of thermal equilibrium.
The Zeroth Law defines thermal equilibrium and provides the basis for temperature measurement by establishing transitivity of thermal equilibrium.
Internal energy of an ideal gas depends on which of the following?
- A. Pressure and volume only
- B. Temperature only
- C. Volume and temperature only
- D. Pressure only
Answer: B. Temperature only
For an ideal gas, internal energy is a function of temperature alone and is independent of pressure and volume.
For an ideal gas, internal energy is a function of temperature alone and is independent of pressure and volume.
Which process occurs at constant temperature?
- A. Isochoric process
- B. Isobaric process
- C. Isothermal process
- D. Adiabatic process
Answer: C. Isothermal process
An isothermal process is defined as a process that occurs at constant temperature, where ΔT = 0.
An isothermal process is defined as a process that occurs at constant temperature, where ΔT = 0.
In an adiabatic process, what is the value of heat exchange (Q)?
- A. Q = W
- B. Q = 0
- C. Q = ΔU
- D. Q = pΔV
Answer: B. Q = 0
An adiabatic process is one where no heat is exchanged with the surroundings, so Q = 0 by definition.
An adiabatic process is one where no heat is exchanged with the surroundings, so Q = 0 by definition.
A gas undergoes a process where its volume decreases while pressure increases proportionally. Which process is this?
- A. Isothermal process
- B. Isobaric process
- C. Isochoric process
- D. Adiabatic process
Answer: A. Isothermal process
In an isothermal process, PV = constant; if volume decreases, pressure increases proportionally to maintain constant temperature.
In an isothermal process, PV = constant; if volume decreases, pressure increases proportionally to maintain constant temperature.
During an adiabatic compression of an ideal gas, what happens to its internal energy and temperature?
- A. Internal energy decreases, temperature decreases
- B. Internal energy increases, temperature increases
- C. Internal energy remains constant, temperature increases
- D. Internal energy increases, temperature remains constant
Answer: B. Internal energy increases, temperature increases
In adiabatic compression, work is done on the gas (W < 0), so from ΔU = Q - W = -W, internal energy increases, causing temperature to rise.
In adiabatic compression, work is done on the gas (W < 0), so from ΔU = Q - W = -W, internal energy increases, causing temperature to rise.
A gas expands isothermally against a constant external pressure. Compared to a reversible isothermal expansion, the work done by the gas is:
- A. More in irreversible process
- B. Less in irreversible process
- C. The same in both processes
- D. Cannot be compared without knowing the volume change
Answer: B. Less in irreversible process
Irreversible processes (against constant external pressure) do less work than reversible processes for the same initial and final states.
Irreversible processes (against constant external pressure) do less work than reversible processes for the same initial and final states.
A system undergoes a process where both pressure and volume increase. Which process could this be?
- A. Isothermal process only
- B. Adiabatic process only
- C. Isobaric process only
- D. Cannot occur in any of the standard processes
Answer: D. Cannot occur in any of the standard processes
In isothermal (PV=const), V↑→P↓; in adiabatic (PV^γ=const), V↑→P↓; in isobaric, P is constant. Simultaneous increase requires heating at constant volume impossible with ideal gas laws.
In isothermal (PV=const), V↑→P↓; in adiabatic (PV^γ=const), V↑→P↓; in isobaric, P is constant. Simultaneous increase requires heating at constant volume impossible with ideal gas laws.
A Carnot engine operates between two reservoirs at temperatures 400 K and 300 K. If it absorbs 1000 J from hot reservoir, what is the maximum work output?
- A. 750 J
- B. 250 J
- C. 333 J
- D. 500 J
Answer: B. 250 J
Carnot efficiency η = 1 - T_c/T_h = 1 - 300/400 = 1/4 = 0.25. Work = η × Q_h = 0.25 × 1000 = 250 J.
Carnot efficiency η = 1 - T_c/T_h = 1 - 300/400 = 1/4 = 0.25. Work = η × Q_h = 0.25 × 1000 = 250 J.
A gas is compressed such that PV^1.5 = constant. This process is neither isothermal nor adiabatic. What can be inferred about this process?
- A. Heat is absorbed by the gas during compression
- B. Heat is released by the gas during compression
- C. The process occurs at constant entropy
- D. The internal energy remains constant throughout
Answer: B. Heat is released by the gas during compression
Since 1 < 1.5 < γ (for diatomic, γ ≈ 1.4), this polytropic process lies between isothermal and adiabatic. During compression, temperature rises less than adiabatic, so heat is released.
Since 1 < 1.5 < γ (for diatomic, γ ≈ 1.4), this polytropic process lies between isothermal and adiabatic. During compression, temperature rises less than adiabatic, so heat is released.