Heat & Thermodynamics · JEE Main previous year questions

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2026 19 questions

Q362026 · 8 Apr 2026 · Shift 2
Initial pressure and volume of a monoatomic ideal gas are $P$ and $V$ . The change in internal energy of this gas in adiabatic expansion to volume $V_{f ina l} = 27 V$ is ____ $J$ .
1. A. $- 2 P V (33 - 1)$
2. B. $\frac{4}{3} P V$
3. C. $- \frac{4}{3} P V$
4. D. $\frac{3}{4} P V$
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Answer: C
Q382026 · 8 Apr 2026 · Shift 2
A monochromatic source of light operating at $15 kW$ emits $2.5 \times 1 0^{22} photons/s$ . The region of an electromagnetic spectrum to which the emitted electromagnetic radiation belongs to ____ . (Take $h = 6.6 \times 1 0^{- 34} J \cdot s$ and $c = 3 \times 1 0^{8} m/s$ ).
1. A.Microwave
2. B.Infrared
3. C.Visible
4. D.Ultraviolet
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Answer: D
Q502026 · 6 Apr 2026 · Shift 1· Numerical answer
A certain gas is isothermally compressed to $(\frac{1}{3})^{rd}$ of its initial volume ( $V_{o} = 3 litre$ ) by applying required pressure. If the bulk modulus of the gas is $3 \times 1 0^{5} N/ m^{2}$ , the magnitude of work done on the gas is ____ $J$ .
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Answer: 600
Q302026 · 6 Apr 2026 · Shift 2
A cylinder with adiabatic walls is closed at both ends and is divided into two compartments by a frictionless adiabatic piston. Ideal gas is filled in both (left and right) the compartments at same $P$ , $V$ , $T$ . Heating is started from left side until pressure changes to $^{27} /_{8} P$ . If initial volume of each compartment was 9 litres then the final volume in right-hand side compartment is ____ litres. (for this ideal gas $C_{P} / C_{V} = 1.5$ )
1. A. $3$
2. B. $4$
3. C. $14$
4. D. $9$
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Answer: B
Q322026 · 5 Apr 2026 · Shift 1
Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R Statement I: Change in internal energy of a system containing $n$ mole of ideal gas can be written as $Δ U = n C_{v} (T_{f} - T_{i}) = \frac{n R}{γ - 1} (T_{f} - T_{i})$ , where $γ = \frac{C _{p}}{C _{v}}$ , $T_{i} = initial temperature$ , $T_{f} = final temperature$ . Statement II: Relation between degree of freedom $f$ and $γ$ ( $= C_{p} / C_{v}$ ) is $(γ = 1 + \frac{2}{f})$ 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 true but R is false
4. D.A is false but R is true
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Answer: B
Q332026 · 5 Apr 2026 · Shift 1
Consider the following statements: A. Zeroth law of thermodynamics gives concept of temperature B. First law of thermodynamics gives concept of internal energy C. In isothermal expansion of ideal gas, $Δ Q \neq = Δ W$ D. Product of intensive and extensive variables is extensive E. The ratio of any extensive variable to mass will be an extensive variable Choose the correct combination of statements from the options given below:
1. A.C, D and E Only
2. B.A, B and C Only
3. C.A, B and D Only
4. D.B, C and D Only
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Answer: C
Q472026 · 5 Apr 2026 · Shift 2· Numerical answer
The heat extracted out of $x gram$ of water initially at $50^{\circ} C$ to cool it down to $0^{\circ} C$ is sufficient to evaporate $(1000 - x) gram$ of water also initially at $50^{\circ} C$ . The value of $x$ (closest integer ) is ____. (Take latent heat of water $2256 kJ/kg \cdot K$ , specific heat capacity of water $4200 J/kg \cdot K$ )
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Answer: 922
Q342026 · 4 Apr 2026 · Shift 2
The temperature of a metal strip having coefficient of linear expansion $α$ is increased from $T_{1}$ to $T_{2}$ resulting in increase of its length by $Δ L_{1}$ . The temperature is further increased from $T_{2}$ to $T_{3}$ such that the increase in its length is $Δ L_{2}$ . Given $T_{3} + T_{1} = 2 T_{2}$ and $T_{2} - T_{1} = Δ T$ , the value of $Δ L_{2}$ is ____.
1. A. $Δ L_{1} [1 + 2 α^{2} (Δ T)^{2}]$
2. B. $Δ L_{1} [1 + α^{2} (Δ T)^{2}]$
3. C. $Δ L_{1} [1 + 2 α Δ T]$
4. D. $Δ L_{1} [1 + α Δ T]$
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Answer: D
Q472026 · 2 Apr 2026 · Shift 1· Numerical answer
A vessel contains $0.15 m^{3}$ of a gas at pressure $8 bar$ and temperature $14 0^{\circ} C$ with $c_{p} = 3 R$ and $c_{v} = 2 R$ . It is expanded adiabatically till pressure falls to $1 bar$ . The work done during this process is ____ $k J$ . ( $R$ is gas constant)
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Answer: 120
Q482026 · 2 Apr 2026 · Shift 2· Numerical answer
5 moles of unknown gas is heated at constant volume from $10^{\circ} C$ to $20^{\circ} C$ . The molar specific heat of this gas at constant pressure $c_{p} = 8 cal/mol.^{\circ} C$ and $R = 8.36 J/mol .^{\circ} C$ . The change in the internal energy of the gas is ____ calorie.
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Answer: 300
Q272026 · 28 Jan 2026 · Shift 1
1. A.
2. B.
3. C.
4. D.
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Answer: C
Q402026 · 28 Jan 2026 · Shift 1
$10 kg$ of ice at $- 1 0^{\circ} C$ is added to $100 kg$ of water to lower its temperature from $2 5^{\circ} C$ . Consider no heat exchange to surroundings. The decrement to the temperature of water is ____ $^{\circ} C$ . (specific heat of $ice = 2100 J/Kg \cdot^{\circ} C$ , specific heat of $water = 4200 J/Kg \cdot^{\circ} C$ , latent heat of fusion of $ice = 3.36 \times 1 0^{5} J/Kg$ )
1. A.15
2. B.10
3. C.6.67
4. D.11.6
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Answer: B
Q442026 · 24 Jan 2026 · Shift 1
Density of water at $4^{\circ} C$ and $2 0^{\circ} C$ are $1000 kg/ m^{3}$ and $998 kg/ m^{3}$ respectively. The increase in internal energy of $4 kg$ of water when it is heated from $4^{\circ} C$ to $2 0^{\circ} C$ is ____ J. (specific heat capacity of water $= 4.2 kJ/kg K$ and $1 atmospheric pressure = 1 0^{5} Pa$ )
1. A.268799.2
2. B.315826.2
3. C.234699.2
4. D.258700.8
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Answer: A
Q342026 · 23 Jan 2026 · Shift 1
In a perfectly inelastic collision, two spheres made of the same material with masses 15 kg and 25 kg , moving in opposite directions with speeds of $10 m/s$ and $30 m/s$ , respectively, strike each other and stick together. The rise in temperature (in $^{\circ} C$ ), if all the heat produced during the collision is retained by these spheres, is : (specific heat of sphere material $31 cal/kg \cdot^{\circ} C$ and $1 cal = 4.2 J$ )
1. A.1.75
2. B.1.44
3. C.1.95
4. D.1.15
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Answer: B
Q262026 · 23 Jan 2026 · Shift 2
One mole of an ideal diatomic gas expands from volume $V$ to $2 V$ isothermally at a temperature $2 7^{\circ} C$ and does $W$ joule of work. If the gas undergoes same magnitude of expansion adiabatically from $2 7^{\circ} C$ doing the same amount of work $W$ , then its final temperature will be (close to) _____ $^{\circ} C$ . $(lo g_{e} 2 = 0.693)$
1. A.-56
2. B.-117
3. C.-30
4. D.-189
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Answer: A
Q322026 · 22 Jan 2026 · Shift 1
Match the LIST-I with LIST-II $List-I A. B. C. D. Spring constant Thermal conductivity Boltzmann constant Inductive reactance List-II I. II. III. IV. M L^{2} T^{- 2} K^{- 1} M L^{0} T^{- 2} M L^{2} T^{- 3} A^{- 2} M L T^{- 3} K^{- 1}$ Choose the correct answer from the options given below:
1. A.A-III, B-II, C-IV, D-I
2. B.A-I, B-IV, C-II, D-III
3. C.A-II, B-I, C-IV, D-III
4. D.A-II, B-IV, C-I, D-III
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Answer: D
Q382026 · 21 Jan 2026 · Shift 1
A gas based geyser heats water flowing at the rate of 5.0 litres per minute from $2 7^{\circ} C$ to $8 7^{\circ} C$ . The rate of consumption of the gas is ____ $g/s$ . (Take heat of combustion of gas $= 5.0 \times 1 0^{4} J/g$ , specific heat capacity of water $= 4200 J/kg \cdot^{\circ} C$ )
1. A.4.2
2. B.2.1
3. C.0.21
4. D.0.42
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Answer: D
Q462026 · 21 Jan 2026 · Shift 1· Numerical answer
10 mole of oxygen is heated at constant volume from $3 0^{\circ} C$ to $4 0^{\circ} C$ . The change in the internal energy of the gas is ____ cal. (The molecular specific heat of oxygen at constant pressure, $C_{P} = 7 cal/mol.^{\circ} C$ and $R = 2 cal./mol.^{\circ} C.$ )
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Answer: 500
Q492026 · 21 Jan 2026 · Shift 2· Numerical answer
A diatomic gas $(γ = 1.4)$ does 100 J of work when it is expanded isobarically. Then the heat given to the gas ____ J.
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Answer: 350