Operating between two temperatures $T_1$ (source) and $T_2$ (sink) have maximum efficiency

Consisting of two isothemal processes connected by two adiabatic processes

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JEE • PHYSICS • THERMODYNAMICS

Thermodynamics practice · Medium

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These sets use single-correct-answer MCQs. They do not cover every JEE Main or JEE Advanced question format and are not full-length mock papers.

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Showing 1-30 of 363 questions

1 Medium

1 of 363

Understanding +4 | -1

The work done in which of the following process is zero?

View answer and explanation

Correct option: C

Isochoric process

Option C (Isochoric process) is correct because in an isochoric process, the volume remains constant, resulting in zero work done.

2 Medium

2 of 363

Understanding +4 | -1

Water is used to cool the radiators of engines in cars because

View answer and explanation

Correct option: B

Of its high specific heat

Option B (Of its high specific heat) is correct because water's high specific heat allows it to absorb a large amount of heat with a small temperature change.

3 Medium

3 of 363

Remembering +4 | -1

A thermodynamic process in which temperature

T

of the system remains constant though other variable

P

and

V

may change, is called

View answer and explanation

Correct option: B

Isothermal process

Option B (Isothermal process) is correct because an isothermal process is defined as a thermodynamic process that occurs at a constant temperature.

4 Medium

4 of 363

Understanding +4 | -1

What is the slope for an isothermal process?

View answer and explanation

Correct option: B

-\frac{P}{V}

Option B is correct because the slope of an isothermal process is given by

-P/V

5 Medium

5 of 363

Understanding +4 | -1

For adiabatic processes

\left( {\gamma = \frac{{{C_p}}}{{{C_v}}}} \right)

View answer and explanation

Correct option: C

T{V^{\gamma - 1}} =

constant

Option C is correct because for adiabatic processes, the relation between temperature and volume is given by

T{V^{\gamma - 1}} = constant

6 Medium

6 of 363

Application +4 | -1

When an ideal gas

\left( {\gamma = 5/3} \right)

is heated under constant pressure, then what percentage of given heat energy will be utilised in doing external work

View answer and explanation

Correct option: A

0.4

Option A (0.4) is correct because the fraction of heat used for external work in a constant pressure process is related to γ by the formula

\frac{Δ W}{Δ Q}

= 1 -

\frac{1}{γ}

7 Medium

7 of 363

Application +4 | -1

Two heat engines

A

and

B

have their sources at 1000 K and 1100 K and their sinks are at 500 K and 400 K respectively. What is true about their efficiencies?

View answer and explanation

Correct option: C

{\eta _A} < {\eta _B}

Option C (

{\eta _A} < {\eta _B}

) is correct because the efficiency of a heat engine depends on the temperatures of the source and sink, and engine B has a higher efficiency.

8 Medium

8 of 363

Understanding +4 | -1

Which of the following is unique function of initial and final states?

View answer and explanation

Correct option: C

Option C (dU) is correct because internal energy (U) is a state function, meaning it depends only on the initial and final states, not the path taken.

9 Medium

9 of 363

Application +4 | -1

The temperature of an air bubble while rising from bottom to surface of a lake remains constant but its diameter is doubled if the pressure on the surface is equal to h meter of mercury column and relative density of mercury is

\rho

then the depth of lake is

View answer and explanation

Correct option: D

7 \rho \mathrm{hm}

Option D (

7 \rho \mathrm{hm}

) is correct because it is derived from Boyle's law, considering the pressure difference between the bottom and surface of the lake.

10 Medium

10 of 363

Analyzing +4 | -1

Assertion: A quasi-static isothermal expansion of an ideal gas in a cylinder fitted with a frictionless movable piston is an irreversible process.
Reason: A process is irreversible only if system remains in equilibrium with the surroundings at every stage.

View answer and explanation

Correct option: D

If both assertion and reason are false

Option D is correct because a quasi-static isothermal expansion is a reversible process, and a process is irreversible if the system is NOT in equilibrium at every stage.

11 Medium

11 of 363

Application +4 | -1

Compressed by doing work on it A gas is compressed adiabatically till its temperature is doubled. The ratio of its final volume to initial volume will be

View answer and explanation

Correct option: C

Less than

1/2

Option C (Less than

1/2

) is correct because the final volume to initial volume ratio is less than 1/2 due to the adiabatic compression.

12 Medium

12 of 363

Understanding +4 | -1

Work done per mole in an isothermal change is

View answer and explanation

Correct option: C

RT{\log _e}\frac{{{V_2}}}{{{V_1}}}

Option C (

RT{\log _e}\frac{{{V_2}}}{{{V_1}}}

) is correct because it represents the work done in an isothermal process derived from integrating

PdV

with

P = \frac{RT}{V}

13 Medium

13 of 363

Understanding +4 | -1

A container of volume

1{m^3}

is divided into two equal compartments by a partition. One of these compartments contains an ideal gas at

300K

. The other compartment is vacuum. The whole system is thermally isolated from its surroundings. The partition is removed and the gas expands to occupy the whole volume of the container. Its temperature now would be

View answer and explanation

Correct option: A

300K

Option A is correct because the expansion is a free expansion into a vacuum, and since the system is thermally isolated, no work is done and the temperature remains constant.

14 Medium

14 of 363

Analyzing +4 | -1

A gas can expand through two processes : (i) isobaric, (ii)

\frac{p}{V}=

constant. Assuming that the initial volume is same in both processes and the final volume which is two times the initial volume is also same in both processes, which of the following is true?

View answer and explanation

Correct option: B

Work done by gas in process (i) is smaller than the work done by the gas in process (ii)

Option B (Work done by gas in process (i) is smaller than the work done by the gas in process (ii)) is correct because the area under the p-V graph is greater for the process where p is proportional to V.

15 Medium

15 of 363

Analyzing +4 | -1

(A): Air in a cylinder is suddenly compressed by a piston. If the volume after compression is half the original volume the final pressure is twice the initial pressure.
(R): Suddenly compressed process is isobaric process.

View answer and explanation

Correct option: D

Both (A) and (R) are false

Option D (Both (A) and (R) are false) is correct because sudden compression is an adiabatic process, not isobaric, and the final pressure is not simply twice the initial pressure.

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16 Medium

16 of 363

Understanding +4 | -1

For an adiabatic compression the quantity

p V

View answer and explanation

Correct option: A

increases

Option A (increases) is correct because in adiabatic compression, temperature increases, and since

pV \propto T

pV

also increases.

17 Medium

17 of 363

Understanding +4 | -1

The volume of an ideal gas is doubled in an isothermal process. Then, which of the following is true?

View answer and explanation

Correct option: A

Work done by the gas is positive

Option A (Work done by the gas is positive) is correct because in an isothermal expansion, the gas does work on the surroundings.

18 Medium

18 of 363

Understanding +4 | -1

Carnot engine is:

View answer and explanation

Correct option: D

Both (1) and (2) options are correct

Option C (Inside a magnet, its magnetic lines of force move from north pole of a magnet towards its south pole) is correct because inside a magnet, magnetic field lines move from the south pole to the north pole.

19 Medium

19 of 363

Understanding +4 | -1

Assertion: In an isolated system, the entropy increases.
Reason: The processes in an isolated system are isobaric.

View answer and explanation

Correct option: C

If assertion is true but reason is false

Option C (If assertion is true but reason is false) is correct because the entropy of an isolated system always increases, but the processes in an isolated system are adiabatic, not necessarily isobaric.

20 Medium

20 of 363

Remembering +4 | -1

Which of the following is/are thermodynamic coordinate?

View answer and explanation

Correct option: D

All of the above

Option D (All of the above) is correct because volume (V), pressure (P), and temperature (T) are all thermodynamic coordinates used to describe the state of a thermodynamic system.

21 Medium

21 of 363

Understanding +4 | -1

Assertion: Specific heat of metals approaches zero as temperature approaches zero Kelvin.
Reason: As temperature approaches zero Kelvin, effectiveness of degree of freedom decrease.

View answer and explanation

Correct option: A

If both Assertion & Reason are True & the Reason is a correct explanation of the Assertion

The correct answer is A because both the assertion and reason are true, and the reason correctly explains why the specific heat of metals approaches zero as temperature approaches zero Kelvin.

22 Medium

22 of 363

Understanding +4 | -1

The work done in an adiabatic change in a gas depends only on

View answer and explanation

Correct option: C

Change in temperature

Option C (Change in temperature) is correct because the work done in an adiabatic process depends only on the initial and final temperatures.

23 Medium

23 of 363

Application +4 | -1

A vessel containing 6 litres of gas at 0.9 m pressure is connected to an evacuated vessel of volume 4 litres. The resultant pressure inside will be [assuming whole system to be isolated]

View answer and explanation

Correct option: D

0.54 m

Option D (0.54 m) is correct because it is calculated using Boyle's Law for the combined volume.

24 Medium

24 of 363

Understanding +4 | -1

(A): The entropy of the solids is the highest.
(R): Atoms of the solids are arranged in orderly manner.

View answer and explanation

Correct option: A

Both (A) and (R) are true and (R) is the correct explanation of (A)

The entropy of solids is the lowest because their atoms are arranged in an orderly manner, restricting their movement and thus reducing disorder. Therefore, both the assertion and the reason are false.

25 Medium

25 of 363

Understanding +4 | -1

Q

E

and

W

denote respectively the heat added, change in internal energy and the work done in a closed cycle process, then

View answer and explanation

Correct option: A

E = 0

Option A (

E = 0

) is correct because in a closed cyclic process, the system returns to its initial state, resulting in no net change in internal energy.

26 Medium

26 of 363

Understanding +4 | -1

Assertion: Heat is not a state thermodynamic function.
Reason: Heat given in a system depends on process.

View answer and explanation

Correct option: A

If both Assertion & Reason are True & the Reason is a correct explanation of the Assertion

Option A is correct because heat is a path-dependent function, meaning the amount of heat transferred depends on the process, not just the initial and final states.

27 Medium

27 of 363

Understanding +4 | -1

Pressure – Temperature relationship for an ideal gas undergoing adiabatic change is

\left( {\gamma = \frac{{{C_P}}}{{{C_V}}}} \right)

View answer and explanation

Correct option: D

{P^{1 - \gamma }}\,\,{T^\gamma }

= Constant

Option D (

{P^{1 - \gamma }}\,{T^{\gamma }}

= Constant) is correct because it represents the correct pressure-temperature relationship for an adiabatic process.

28 Medium

28 of 363

Understanding +4 | -1

In adiabatic expansion

View answer and explanation

Correct option: B

\Delta U =

negative

Option B (

\Delta U =

negative) is correct because in adiabatic expansion, the work done by the system is at the expense of its internal energy, leading to a decrease in internal energy.

29 Medium

29 of 363

Understanding +4 | -1

Given below are two statements:

Statement I: If heat is added to a system, its temperature must increase.

Statement II: If positive work is done by a system in a thermodynamic process, its volume must increase.

In the light of the above statements, choose the correct answer from the options given below

View answer and explanation

Correct option: D

Statement I is false but Statement II is true

Option D (Statement I is false but Statement II is true) is correct because heat addition doesn't always increase temperature, and positive work implies volume increase.

30 Medium

30 of 363

Application +4 | -1

For two substance ratio of mass is

1: 2

and ratio of specific heat is 2 : 3 and its temperature is

10^{\circ} \mathrm{C}

and

40^{\circ} \mathrm{C}

respectively then find out the temperature of mixture.

View answer and explanation

Correct option: D

32.5^{\circ} \mathrm{C}

Option D (

32.5^{\circ} \mathrm{C}

) is correct because it is calculated using the principle of calorimetry, where heat lost equals heat gained.

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Key Takeaways

✓ This set contains 363 single-correct-answer MCQs on THERMODYNAMICS.
✓ Try each question before opening its answer. Read the explanation where one is available.
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