Heat & Thermodynamics · JEE Main previous year questions

2025 19 questions

1. Q262025 · 8 Apr 2025 · Shift 2

   A monoatomic gas having $\gamma =\frac{5}{3}$ is stored in a thermally insulated container and the gas is suddenly compressed to ${\left(\frac{1}{8}\right)}^{\mathrm{th}}$ of its initial volume. The ratio of final pressure and initial pressure is: ($\gamma$ is the ratio of specific heats of the gas at constant pressure and at constant volume)

   1. A.$16$
   2. B.$32$
   3. C.$28$
   4. D.$40$
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   Answer: B

2. Q352025 · 8 Apr 2025 · Shift 2

   Water falls from a height of $200\mathrm{m}$ into a pool. Calculate the rise in temperature of the water assuming no heat dissipation from the water in the pool. (Take $g=10{m/s}^2$, specific heat of water $=4200J/(\mathrm{kg}\mathrm{K})$)

   1. A.$0.36\mathrm{K}$
   2. B.$0.23\mathrm{K}$
   3. C.$0.48\mathrm{K}$
   4. D.$0.14\mathrm{K}$
   Show answer

   Answer: C

3. Q332025 · 4 Apr 2025 · Shift 2

   Consider a rectangular sheet of solid material of length $l=9\mathrm{cm}$ and width $\mathrm{d}=4\mathrm{cm}$. The coefficient of linear expansion is $\alpha =3.1\times 10^{-5}{\mathrm{K}}^{-1}$ at room temperature and one atmospheric pressure. The mass of sheet $m=0.1\mathrm{kg}$ and the specific heat capacity $C_v=900\mathrm{J}\mathrm{k}{\mathrm{g}}^{-1}{\mathrm{K}}^{-1}$. If the amount of heat supplied to the material is $8.1\times 10^2\mathrm{J}$ then change in area of the rectangular sheet is :

   1. A.$2.0\times 10^{-6}{\mathrm{m}}^2$
   2. B.$6.0\times 10^{-7}{\mathrm{m}}^2$
   3. C.$3.0\times 10^{-7}{\mathrm{m}}^2$
   4. D.$4.0\times 10^{-7}{\mathrm{m}}^2$
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   Answer: A

4. Q412025 · 4 Apr 2025 · Shift 2

   Match List - I with List - II. $$\begin{array}{llll}& \text{List - I}& & \text{List - II}\\ \text{(A)}& \text{Isobaric}& \text{(I)}& \Delta Q=\Delta W\\ \text{(B)}& \text{Isochoric}& \text{(II)}& \Delta Q=\Delta U\\ \text{(C)}& \text{Adiabatic}& \text{(III)}& \Delta Q=\text{zero}\\ \text{(D)}& \text{Isothermal}& \text{(IV)}& \Delta Q=\Delta U+P\Delta V\end{array}$$ $\Delta Q=$ Heat supplied $\Delta W=$ Work done by the system $\Delta \mathrm{U}=$ Change in internal energy $\mathrm{P}=$ Pressure of the system $\Delta \mathrm{V}=$ Change in volume of the system Choose the correct answer from the options given below :

   1. A.(A)-(IV), (B)-(I), (C)-(III), (D)-(II)
   2. B.(A)-(IV), (B)-(II), (C)-(III), (D)-(I)
   3. C.(A)-(IV), (B)-(III), (C)-(II), (D)-(I)
   4. D.(A)-(II), (B)-(IV), (C)-(III), (D)-(I)
   Show answer

   Answer: B

5. Q262025 · 3 Apr 2025 · Shift 1

   A gas is kept in a container having walls which are thermally non-conducting. Initially the gas has a volume of $800\mathrm{c}{\mathrm{m}}^3$ and temperature $27^{\circ }\mathrm{C}$. The change in temperature when the gas is adiabatically compressed to $200\mathrm{c}{\mathrm{m}}^3$ is: (Take $\gamma =1.5$; $\gamma$ is the ratio of specific heats at constant pressure and at constant volume)

   1. A.$300\mathrm{K}$
   2. B.$600\mathrm{K}$
   3. C.$327\mathrm{K}$
   4. D.$522\mathrm{K}$
   Show answer

   Answer: A

6. Q312025 · 3 Apr 2025 · Shift 2

   An ideal gas exists in a state with pressure $P_0$, volume $V_0$. It is isothermally expanded to 4 times of its initial volume ($V_0$), then isobarically compressed to its original volume. Finally the system is heated isochorically to bring it to its initial state. The amount of heat exchanged in this process is

   1. A.${\mathrm{P}}_0{\mathrm{V}}_0(\ln 2-0.75)$
   2. B.${\mathrm{P}}_0{\mathrm{V}}_0(2\ln 2-0.75)$
   3. C.${\mathrm{P}}_0{\mathrm{V}}_0(2\ln 2-0.25)$
   4. D.${\mathrm{P}}_0{\mathrm{V}}_0(\ln 2-0.25)$
   Show answer

   Answer: B

7. Q392025 · 3 Apr 2025 · Shift 2

   Match the LIST-I with LIST-II \begin{tabular}{|l|l|l|l|} \hline \textbf{LIST-I} & & \textbf{LIST-II} & \\ \hline A. & Boltzmann constant & I & ${\mathrm{ML}}^2{\mathrm{T}}^{-1}$ \\ B & Coefficient of viscosity & II & ${\mathrm{MLT}}^{-3}{\mathrm{K}}^{-1}$ \\ C & Planck's constant & III & ${\mathrm{ML}}^2{\mathrm{T}}^{-2}{\mathrm{K}}^{-1}$ \\ D & Thermal conductivity & IV & ${\mathrm{ML}}^{-1}{\mathrm{T}}^{-1}$ \\ \hline \end{tabular} Choose the correct answer from the options given below:

   1. A.A - III, B - IV, C - I, D - II
   2. B.A - III, B - IV, C - II, D - I
   3. C.A - III, B - II, C - I, D - IV
   4. D.A - II, B - III, C - IV, D - I
   Show answer

   Answer: A

8. Q392025 · 2 Apr 2025 · Shift 1

   In an adiabatic process, which of the following statements is true?

   1. A.The internal energy of the gas decreases as the temperature increases
   2. B.The molar heat capacity is zero
   3. C.Work done by the gas equals the increase in internal energy
   4. D.The molar heat capacity is infinite
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   Answer: B

9. Q472025 · 2 Apr 2025 · Shift 1· Numerical answer

   ${\gamma }_{\mathrm{A}}$ is the specific heat ratio of monoatomic gas A having 3 translational degrees of freedom. ${\gamma }_B$ is the specific heat ratio of polyatomic gas $B$ having 3 translational, 3 rotational degrees of freedom and 1 vibrational mode. If $\frac{{\gamma }_{\mathrm{A}}}{{\gamma }_B}=\left(1+\frac{1}{n}\right)$, then the value of $n$ is _________ .

   Show answer

   Answer: 3

10. Q402025 · 2 Apr 2025 · Shift 2

    Match List - I with List - II. $$\begin{array}{llll}& \text{List - I}& & List-II\\ \text{(A)}& \text{Heat capacity of body}& \text{(I)}& \mathrm{J}\mathrm{k}{\mathrm{g}}^{-1}\\ \text{(B)}& \text{Specific heat capacity of body}& \text{(II)}& \mathrm{J}{\mathrm{K}}^{-1}\\ \text{(C)}& \text{Latent heat}& \text{(III)}& \mathrm{J}\mathrm{k}{\mathrm{g}}^{-1}{\mathrm{K}}^{-1}\\ \text{(D)}& \text{Thermal conductivity}& \text{(IV)}& \mathrm{J}{\mathrm{m}}^{-1}{\mathrm{K}}^{-1}{\mathrm{s}}^{-1}\end{array}$$ Choose the correct answer from the options given below :

    1. A.(A)-(IV), (B)-(III), (C)-(II), (D)-(I)
    2. B.(A)-(III), (B)-(I), (C)-(II), (D)-(IV)
    3. C.(A)-(III), (B)-(IV), (C)-(I), (D)-(II)
    4. D.(A)-(II), (B)-(III), (C)-(I), (D)-(IV)
    Show answer

    Answer: D

11. Q432025 · 2 Apr 2025 · Shift 2

    Identify the characteristics of an adiabatic process in a monoatomic gas. (A) Internal energy is constant. (B) Work done in the process is equal to the change in internal energy. (C) The product of temperature and volume is a constant. (D) The product of pressure and volume is a constant. (E) The work done to change the temperature from ${\mathrm{T}}_1$ to ${\mathrm{T}}_2$ is proportional to $({\mathrm{T}}_2-{\mathrm{T}}_1)$. Choose the correct answer from the options given below :

    1. A.(B), (D) only
    2. B.(B), (E) only
    3. C.(A), (C), (E) only
    4. D.(A), (C), (D) only
    Show answer

    Answer: B

12. Q302025 · 29 Jan 2025 · Shift 2

    Given below are two statements. One is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A) : With the increase in the pressure of an ideal gas, the volume falls off more rapidly in an isothermal process in comparison to the adiabatic process. Reason (R) : In isothermal process, $\mathrm{PV}=\mathrm{constant}$, while in adiabatic process $P{V}^{\gamma }=\mathrm{constant}$. Here $\gamma$ is the ratio of specific heats, P is the pressure and V is the volume of the ideal gas. In the light of the above statements, choose the correct answer from the options given below:

    1. A.(A) is true but (R) is false
    2. B.Both (A) and (R) are true but (R) is NOT the correct explanation of (A)
    3. C.(A) is false but (R) is true
    4. D.Both (A) and (R) are true and (R) is the correct explanation of (A)
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    Answer: D

13. Q402025 · 29 Jan 2025 · Shift 2
    
    1. A.$500\mathrm{R}(\ln 3+\ln 4)$
    2. B.$450\mathrm{R}(\ln 4-\ln 3)$
    3. C.$500\mathrm{R}\ln 2$
    4. D.$400\mathrm{R}\ln 4$
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    Answer: B

14. Q452025 · 28 Jan 2025 · Shift 1

    A Carnot engine ($\mathrm{E}$) is working between two temperatures $473\mathrm{K}$ and $273\mathrm{K}$ . In a new system two engines - engine $E_1$ works between $473\mathrm{K}$ to $373\mathrm{K}$ and engine $E_2$ works between $373\mathrm{K}$ to $273\mathrm{K}$ . If ${\eta }_{12},{\eta }_1$ and ${\eta }_2$ are the efficiencies of the engines $E,E_1$ and $E_2$, respectively, then

    1. A.${\eta }_{12}={\eta }_1{\eta }_2$
    2. B.${\eta }_{12}={\eta }_1+{\eta }_2$
    3. C.${\eta }_{12}\ge {\eta }_1+{\eta }_2$
    4. D.${\eta }_{12}<{\eta }_1+{\eta }_2$
    Show answer

    Answer: D

15. Q342025 · 24 Jan 2025 · Shift 1

    An ideal gas goes from an initial state to final state. During the process, the pressure of gas increases linearly with temperature. A. The work done by gas during the process is zero. B. The heat added to gas is different from change in its internal energy. C. The volume of the gas is increased. D. The internal energy of the gas is increased. E. The process is isochoric (constant volume process) Choose the correct answer from the options given below:

    1. A.A, C Only
    2. B.A, D, E Only
    3. C.E Only
    4. D.A, B, C, D Only
    Show answer

    Answer: B

16. Q362025 · 24 Jan 2025 · Shift 2

    Given below are two statements. One is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A) : In an insulated container, a gas is adiabatically shrunk to half of its initial volume. The temperature of the gas decreases. Reason (R) : Free expansion of an ideal gas is an irreversible and an adiabatic process. In the light of the above statements, choose the correct answer from the options given below :

    1. A.Both (A) and (R) are true and (R) is the correct explanation of (A)
    2. B.Both (A) and (R) are true but (R) is NOT the correct explanation of (A)
    3. C.(A) is false but (R) is true
    4. D.(A) is true but (R) is false
    Show answer

    Answer: C

17. Q302025 · 23 Jan 2025 · Shift 2

    Water of mass $m$ gram is slowly heated to increase the temperature from $T_1$ to $T_2$. The change in entropy of the water, given specific heat of water is $1{\mathrm{Jkg}}^{-1}{\mathrm{K}}^{-1}$, is :

    1. A.$\mathrm{m}({\mathrm{T}}_2-{\mathrm{T}}_1)$
    2. B.zero
    3. C.$\mathrm{m}\ln \left(\frac{{\mathrm{T}}_1}{{\mathrm{T}}_2}\right)$
    4. D.$\mathrm{m}\ln \left(\frac{{\mathrm{T}}_2}{{\mathrm{T}}_1}\right)$
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    Answer: D

18. Q342025 · 22 Jan 2025 · Shift 1

    An amount of ice of mass $10^{-3}\text{ kg}$ and temperature $-10^{\circ }\mathrm{C}$ is transformed to vapour of temperature $110^{\circ }\mathrm{C}$ by applying heat. The total amount of work required for this conversion is, (Take, specific heat of ice $=2100{\text{ J kg}}^{-1}{\text{ K}}^{-1}$, specific heat of water $=4180{\text{ J kg}}^{-1}{\text{ K}}^{-1}$, specific heat of steam $=1920{\text{ J kg}}^{-1}{\text{ K}}^{-1}$, Latent heat of ice $=3.35\times 10^5{\text{ J kg}}^{-1}$ and Latent heat of steam $=2.25\times 10^6{\text{ J kg}}^{-1}$ )

    1. A.$3022\text{ J}$
    2. B.$3043\text{ J}$
    3. C.$3003\text{ J}$
    4. D.$3024\text{ J}$
    Show answer

    Answer: B

19. Q482025 · 22 Jan 2025 · Shift 1· Numerical answer
    
    Show answer

    Answer: 40