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Heat and Thermodynamics

486 Questions Start JEE Mains Test
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2021 Q251 JEE Mains MCQ
10 Mar 2026
The height of victoria falls is 63 m. What is the difference in temperature of water at the top and at the bottom of fall?

[Given 1 cal = 4.2 J and specific heat of water = 1 cal g$-$1 $^\circ$0C$-$1]
A.
0.147$^\circ$ C
B.
14.76$^\circ$ C
C.
1.476$^\circ$ C
D.
0.014$^\circ$ C
2021 Q252 JEE Mains MCQ
10 Mar 2026
A balloon carries a total load of 185 kg at normal pressure and temperature of 27$^\circ$C. What load will the balloon carry on rising to a height at which the barometric pressure is 45 cm of Hg and the temperature is $-$7$^\circ$C. Assuming the volume constant?
A.
181.46 kg
B.
214.15 kg
C.
219.07 kg
D.
123.54 kg
2021 Q253 JEE Mains MCQ
10 Mar 2026
An ideal gas is expanding such that PT3 = constant. The coefficient of volume expansion of the gas is :
A.
${1 \over T}$
B.
${2 \over T}$
C.
${4 \over T}$
D.
${3 \over T}$
2021 Q254 JEE Mains MCQ
10 Mar 2026
The temperature of equal masses of three different liquids x, y and z are 10$^\circ$C, 20$^\circ$C and 30$^\circ$C respectively. The temperature of mixture when x is mixed with y is 16$^\circ$C and that when y is mixed with z is 26$^\circ$C. The temperature of mixture when x and z are mixed will be :
A.
28.32$^\circ$C
B.
25.62$^\circ$C
C.
23.84$^\circ$C
D.
20.28$^\circ$C
2021 Q255 JEE Mains MCQ
10 Mar 2026
A cylindrical container of volume 4.0 $\times$ 10$-$3 m3 contains one mole of hydrogen and two moles of carbon dioxide. Assume the temperature of the mixture is 400 K. The pressure of the mixture of gases is :

[Take gas constant as 8.3 J mol$-$1 K$-$1]
A.
249 $\times$ 101 Pa
B.
24.9 $\times$ 103 Pa
C.
24.9 $\times$ 105 Pa
D.
24.9 Pa
2021 Q256 JEE Mains MCQ
10 Mar 2026
A refrigerator consumes an average 35W power to operate between temperature $-$10$^\circ$C to 25$^\circ$C. If there is no loss of energy then how much average heat per second does it transfer?
A.
263 J/s
B.
298 J/s
C.
350 J/s
D.
35 J/s
2021 Q257 JEE Mains MCQ
10 Mar 2026
An electric appliance supplies 6000 J/min heat to the system. If the system delivers a power of 90W. How long it would take to increase the internal energy by 2.5 $\times$ 103 J ?
A.
2.5 $\times$ 102 s
B.
4.1 $\times$ 101 s
C.
2.4 $\times$ 103 s
D.
2.5 $\times$ 101 s
2021 Q258 JEE Mains MCQ
10 Mar 2026
The rms speeds of the molecules of Hydrogen, Oxygen and Carbon dioxide at the same temperature are VH, VO and VC respectively then :
A.
VH > VO > VC
B.
VC > VO > VH
C.
VH = VO > VC
D.
VH = VO = VC
2021 Q259 JEE Mains MCQ
10 Mar 2026
One mole of an ideal gas is taken through an adiabatic process where the temperature rises from 27$^\circ$ C to 37$^\circ$ C. If the ideal gas is composed of polyatomic molecule that has 4 vibrational modes, which of the following is true? [R = 8.314 J mol$-$1 k$-$1]
A.
work done by the gas is close to 332 J
B.
work done on the gas is close to 582 J
C.
work done by the gas is close to 582 J
D.
work done on the gas is close to 332 J
2021 Q260 JEE Mains MCQ
10 Mar 2026
Two Carnot engines A and B operate in series such that engine A absorbs heat at T1 and rejects heat to a sink at temperature T. Engine B absorbs half of the heat rejected by Engine A and rejects heat to the sink at T3. When workdone in both the cases is equal, to value of T is :
A.
${2 \over 3}{T_1} + {3 \over 2}{T_3}$
B.
${1 \over 3}{T_1} + {2 \over 3}{T_3}$
C.
${3 \over 2}{T_1} + {1 \over 3}{T_3}$
D.
${2 \over 3}{T_1} + {1 \over 3}{T_3}$
2021 Q261 JEE Mains MCQ
10 Mar 2026
The number of molecules in one litre of an ideal gas at 300 K and 2 atmospheric pressure with mean kinetic energy 2 $\times$ 10$-$9 J per molecules is :
A.
0.75 $\times$ 1011
B.
3 $\times$ 1011
C.
1.5 $\times$ 1011
D.
6 $\times$ 1011
2021 Q262 JEE Mains MCQ
10 Mar 2026
In the reported figure, there is a cyclic process ABCDA on a sample of 1 mol of a diatomic gas. The temperature of the gas during the process A $\to$ B and C $\to$ D are T1 and T2 (T1 > T2) respectively.

JEE Main 2021 (Online) 27th July Morning Shift Physics - Heat and Thermodynamics Question 266 English
Choose the correct option out of the following for work done if processes BC and DA are adiabatic.
A.
WAB = WDC
B.
WAD = WBC
C.
WBC + WDA > 0
D.
WAB < WCD
2021 Q263 JEE Mains MCQ
10 Mar 2026
A heat engine has an efficiency of ${1 \over 6}$. When the temperature of sink is reduced by 62$^\circ$C, its efficiency get doubled. The temperature of the source is :
A.
124$^\circ$C
B.
37$^\circ$C
C.
62$^\circ$C
D.
99$^\circ$C
2021 Q264 JEE Mains MCQ
10 Mar 2026
For a gas CP $-$ CV = R in a state P and CP $-$ CV = 1.10 R in a state Q, TP and TQ are the temperatures in two different states P and Q respectively. Then
A.
TP = TQ
B.
TP < TQ
C.
TP = 0.9 TQ
D.
TP > TQ
2021 Q265 JEE Mains MCQ
10 Mar 2026
A monoatomic ideal gas, initially at temperature T1 is enclosed in a cylinder fitted with a frictionless piston. The gas is allowed to expand adiabatically to a temperature T2 by releasing the piston suddenly. If l1 and l2 are the lengths of the gas column, before and after the expansion respectively, then the value of ${{{T_1}} \over {{T_2}}}$ will be :
A.
${\left( {{{{l_1}} \over {{l_2}}}} \right)^{{2 \over 3}}}$
B.
${\left( {{{{l_2}} \over {{l_1}}}} \right)^{{2 \over 3}}}$
C.
${{{l_2}} \over {{l_1}}}$
D.
${{{l_1}} \over {{l_2}}}$
2021 Q266 JEE Mains MCQ
10 Mar 2026
Two different metal bodies A and B of equal mass are heated at a uniform rate under similar conditions. The variation of temperature of the bodies is graphically represented as shown in the figure. The ratio of specific heat capacities is :

JEE Main 2021 (Online) 25th July Morning Shift Physics - Heat and Thermodynamics Question 271 English
A.
${8 \over 3}$
B.
${3 \over 8}$
C.
${3 \over 4}$
D.
${4 \over 3}$
2021 Q267 JEE Mains MCQ
10 Mar 2026
What will be the average value of energy for a monoatomic gas in thermal equilibrium at temperature T?
A.
${3 \over 2}{k_B}T$
B.
${k_B}T$
C.
${2 \over 3}{k_B}T$
D.
${1 \over 2}{k_B}T$
2021 Q268 JEE Mains MCQ
10 Mar 2026
Which of the following graphs represent the behavior of an ideal gas? Symbols have their usual meaning.
A.
JEE Main 2021 (Online) 20th July Evening Shift Physics - Heat and Thermodynamics Question 277 English Option 1
B.
JEE Main 2021 (Online) 20th July Evening Shift Physics - Heat and Thermodynamics Question 277 English Option 2
C.
JEE Main 2021 (Online) 20th July Evening Shift Physics - Heat and Thermodynamics Question 277 English Option 3
D.
JEE Main 2021 (Online) 20th July Evening Shift Physics - Heat and Thermodynamics Question 277 English Option 4
2021 Q269 JEE Mains MCQ
10 Mar 2026
The correct relation between the degrees of freedom f and the ratio of specific heat $\gamma$ is :
A.
$f = {2 \over {\gamma - 1}}$
B.
$f = {2 \over {\gamma + 1}}$
C.
$f = {{\gamma + 1} \over 2}$
D.
$f = {1 \over {\gamma + 1}}$
2021 Q270 JEE Mains MCQ
10 Mar 2026
Consider a mixture of gas molecule of types A, B and C having masses mA < mB < mC. The ratio of their root mean square speeds at normal temperature and pressure is :
A.
${v_A} = {v_B} \ne {v_C}$
B.
${1 \over {{v_A}}} > {1 \over {{v_B}}} > {1 \over {{v_C}}}$
C.
${1 \over {{v_A}}} < {1 \over {{v_B}}} < {1 \over {{v_C}}}$
D.
${v_A} = {v_B} = {v_C} = 0$
2021 Q271 JEE Mains MCQ
10 Mar 2026
The amount of heat needed to raise the temperature of 4 moles of rigid diatomic gas from 0$^\circ$ C to 50$^\circ$ C when no work is done is ___________. (R is the universal gas constant).
A.
500 R
B.
250 R
C.
750 R
D.
175 R
2021 Q272 JEE Mains MCQ
10 Mar 2026
The entropy of any system is given by
$S = {\alpha ^2}\beta \ln \left[ {{{\mu kR} \over {J{\beta ^2}}} + 3} \right]$ where $\alpha$ and $\beta$ are the constants. $\mu$, J, k and R are no. of moles, mechanical equivalent of heat, Boltzmann constant and gas constant respectively.
[Take $S = {{dQ} \over T}$]
Choose the incorrect option from the following :
A.
$\alpha$ and J have the same dimensions.
B.
S and $\alpha$ have different dimensions
C.
S, $\beta$, k and $\mu$R have the same dimensions
D.
$\alpha$ and k have the same dimensions
2021 Q273 JEE Mains MCQ
10 Mar 2026
Consider a sample of oxygen behaving like an ideal gas. At 300 K, the ratio of root mean square (rms) velocity to the average velocity of gas molecule would be :

(Molecular weight of oxygen is 32g/mol; R = 8.3 J K$-$1 mol$-$1)
A.
$\sqrt {{{3\pi } \over 8}} $
B.
$\sqrt {{3 \over 3}} $
C.
$\sqrt {{8 \over 3}} $
D.
$\sqrt {{{8\pi } \over 3}} $
2021 Q274 JEE Mains MCQ
10 Mar 2026
For an adiabatic expansion of an ideal gas, the fractional change in its pressure is equal to (where $\gamma$ is the ratio of specific heats) :
A.
$ - {1 \over \gamma }{{dV} \over V}$
B.
$ - \gamma {V \over {dV}}$
C.
$ - \gamma {{dV} \over V}$
D.
${{dV} \over V}$
2021 Q275 JEE Mains MCQ
10 Mar 2026
An ideal gas in a cylinder is separated by a piston in such a way that the entropy of one part is S1 and that of the other part is S2. Given that S1 > S2. If the piston is removed then the total entropy of the system will be :
A.
S1 $-$ S2
B.
${{{S_1}} \over {{S_2}}}$
C.
S1 $\times$ S2
D.
S1 + S2
2021 Q276 JEE Mains MCQ
10 Mar 2026
The P-V diagram of a diatomic ideal gas system going under cyclic process as shown in figure. The work done during an adiabatic process CD is (use $\gamma$ = 1.4) :

JEE Main 2021 (Online) 18th March Morning Shift Physics - Heat and Thermodynamics Question 285 English
A.
$-$500 J
B.
$-$400 J
C.
400 J
D.
200 J
2021 Q277 JEE Mains MCQ
10 Mar 2026
What will be the average value of energy along one degree of freedom for an ideal gas in thermal equilibrium at a temperature T? (kB is Boltzmann constant)
A.
${1 \over 2}{k_B}T$
B.
${2 \over 3}{k_B}T$
C.
${3 \over 2}{k_B}T$
D.
${k_B}T$
2021 Q278 JEE Mains MCQ
10 Mar 2026
If one mole of the polyatomic gas is having two vibrational modes and $\beta$ is the ratio of molar specific heats for polyatomic gas $\left( {\beta = {{{C_P}} \over {{C_V}}}} \right)$ then the value of $\beta$ is :
A.
1.02
B.
1.35
C.
1.2
D.
1.25
2021 Q279 JEE Mains MCQ
10 Mar 2026
Which one is the correct option for the two different thermodynamic processes?

JEE Main 2021 (Online) 17th March Evening Shift Physics - Heat and Thermodynamics Question 287 English 1
JEE Main 2021 (Online) 17th March Evening Shift Physics - Heat and Thermodynamics Question 287 English 2
JEE Main 2021 (Online) 17th March Evening Shift Physics - Heat and Thermodynamics Question 287 English 3
JEE Main 2021 (Online) 17th March Evening Shift Physics - Heat and Thermodynamics Question 287 English 4
A.
(a) only
B.
(c) and (d)
C.
(b) and (c)
D.
(c) and (a)
2021 Q280 JEE Mains MCQ
10 Mar 2026
A polyatomic ideal gas has 24 vibrational modes. What is the value of $\gamma$?
A.
1.37
B.
1.30
C.
1.03
D.
10.3
2021 Q281 JEE Mains MCQ
10 Mar 2026
Two ideal polyatomic gases at temperatures T1 and T2 are mixed so that there is no loss of energy. If F1 and F2, m1 and m2, n1 and n2 be the degrees of freedom, masses, number of molecules of the first and second gas respectively, the temperature of mixture of these two gases is :
A.
${{{n_1}{F_1}{T_1} + {n_2}{F_2}{T_2}} \over {{F_1} + {F_2}}}$
B.
${{{n_1}{F_1}{T_1} + {n_2}{F_2}{T_2}} \over {{n_1}{F_1} + {n_2}{F_2}}}$
C.
${{{n_1}{T_1} + {n_2}{T_2}} \over {{n_1} + {n_2}}}$
D.
${{{n_1}{F_1}{T_1} + {n_2}{F_2}{T_2}} \over {{n_1} + {n_2}}}$
2021 Q282 JEE Mains MCQ
10 Mar 2026
Two identical metal wires of thermal conductivities K1 and K2 respectively are connected in series. The effective thermal conductivity of the combination is :
A.
${{2{K_1}{K_2}} \over {{K_1} + {K_2}}}$
B.
${{{K_1} + {K_2}} \over {{K_1}{K_2}}}$
C.
${{{K_1} + {K_2}} \over {2{K_1}{K_2}}}$
D.
${{{K_1}{K_2}} \over {{K_1} + {K_2}}}$
2021 Q283 JEE Mains MCQ
10 Mar 2026
A Carnot's engine working between 400 K and 800 K has a work output of 1200 J per cycle. The amount of heat energy supplied to the engine from the source in each cycle is :
A.
2400 J
B.
1600 J
C.
1800 J
D.
3200 J
2021 Q284 JEE Mains MCQ
10 Mar 2026
Calculate the value of mean free path ($\lambda$) for oxygen molecules at temperature 27$^\circ$C and pressure 1.01 $\times$ 105 Pa. Assume the molecular diameter 0.3 nm and the gas is ideal. (k = 1.38 $\times$ 10$-$23 JK$-$1)
A.
32 nm
B.
58 nm
C.
86 nm
D.
102 nm
2021 Q285 JEE Mains MCQ
10 Mar 2026
A bimetallic strip consists of metals A and B. It is mounted rigidly as shown. The metal A has higher coefficient of expansion compared to that of metal B. When the bimetallic strip is placed in a cold bath, it will :

JEE Main 2021 (Online) 16th March Evening Shift Physics - Heat and Thermodynamics Question 293 English
A.
Neither bend nor shrink
B.
Bend towards the left
C.
Not bend but shrink
D.
Bend towards the right
2021 Q286 JEE Mains MCQ
10 Mar 2026
In thermodynamics, heat and work are :
A.
Path functions
B.
Point functions
C.
Extensive thermodynamics state variables
D.
Intensive thermodynamic state variables
2021 Q287 JEE Mains MCQ
10 Mar 2026
The volume V of an enclosure contains a mixture of three gases, 16 g of oxygen, 28 g of nitrogen and 44 g of carbon dioxide at absolute temperature T. Consider R as universal gas constant. The pressure of the mixture of gases is :
A.
${{3RT} \over V}$
B.
${{4RT} \over V}$
C.
${{88RT} \over V}$
D.
${5 \over 2}{{RT} \over V}$
2021 Q288 JEE Mains MCQ
10 Mar 2026
The internal energy (U), pressure (P) and volume (V) of an ideal gas are related as U $=$ 3PV + 4. The gas is :
A.
either monoatomic or diatomic.
B.
monoatomic only.
C.
polyatomic only.
D.
diatomic only.
2021 Q289 JEE Mains MCQ
10 Mar 2026
The temperature $\theta$ at the junction of two insulating sheets, having thermal resistances R1 and R2 as well as top and bottom temperatures $\theta$1 and $\theta$2 (as shown in figure) is given by :

JEE Main 2021 (Online) 26th February Morning Shift Physics - Heat and Thermodynamics Question 301 English
A.
${{{\theta _1}{R_2} + {\theta _2}{R_1}} \over {{R_1} + {R_2}}}$
B.
${{{\theta _1}{R_1} + {\theta _2}{R_2}} \over {{R_1} + {R_2}}}$
C.
${{{\theta _1}{R_2} - {\theta _2}{R_1}} \over {{R_2} - {R_1}}}$
D.
${{{\theta _2}{R_2} - {\theta _1}{R_1}} \over {{R_2} - {R_1}}}$
2021 Q290 JEE Mains MCQ
10 Mar 2026
Given below are two statements :

Statement I : In a diatomic molecule, the rotational energy at a given temperature obeys Maxwell's distribution.

Statement II : In a diatomic molecule, the rotational energy at a given temperature equals the translational kinetic energy for each molecule.

In the light of the above statements, choose the correct answer from the options given below :
A.
Both Statement I and Statement II are true
B.
Both Statement I and Statement II are false
C.
Statement I is true but Statement II is false.
D.
Statement I is false but Statement II is true.
2021 Q291 JEE Mains MCQ
10 Mar 2026
Thermodynamic process is shown below on a P-V diagram for one mole of an ideal gas. If V2 = 2V1 then the ratio of temperature T2/T1 is :

JEE Main 2021 (Online) 25th February Evening Shift Physics - Heat and Thermodynamics Question 304 English
A.
$\sqrt 2 $
B.
${1 \over {\sqrt 2 }}$
C.
${1 \over 2}$
D.
2
2021 Q292 JEE Mains MCQ
10 Mar 2026
Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R.

Assertion A : When a rod lying freely is heated, no thermal stress is developed in it.

Reason R : On heating, the length of the rod increases.

In the light of the above statements, choose the correct answer from the options given below :
A.
A is true but R is false
B.
A is false but R is true
C.
Both A and B are true but R is NOT the correct explanation of A
D.
Both A and R are true and R is the correct explanation of A
2021 Q293 JEE Mains MCQ
10 Mar 2026
A diatomic gas, having ${C_p} = {7 \over 2}R$ and ${C_v} = {5 \over 2}R$, is heated at constant pressure. The ratio dU : dQ : dW :
A.
5 : 7 : 3
B.
3 : 7 : 2
C.
5 : 7 : 2
D.
3 : 5 : 2
2021 Q294 JEE Mains MCQ
10 Mar 2026
If one mole of an ideal gas at (P1, V1) is allowed to expand reversibly and isothermally (A to B) its pressure is reduced to one-half of the original pressure (see figure). This is followed by a constant volume cooling till its pressure is reduced to one-fourth of the initial value (B $ \to $ C). Then it is restored to its initial state by a reversible adiabatic compression (C to A). The net workdone by the gas is equal to :

JEE Main 2021 (Online) 24th February Evening Shift Physics - Heat and Thermodynamics Question 310 English
A.
$ - {{RT} \over {2(\gamma - 1)}}$
B.
$RT\left( {\ln 2 - {1 \over {2(\gamma - 1)}}} \right)$
C.
$RT\ln 2$
D.
$0$
2021 Q295 JEE Mains MCQ
10 Mar 2026
On the basis of kinetic theory of gases, the gas exerts pressure because its molecules :
A.
continuously lose their energy till it reaches wall.
B.
are attracted by the walls of container.
C.
suffer change in momentum when impinge on the walls of container.
D.
continuously stick to the walls of container.
2021 Q296 JEE Mains MCQ
10 Mar 2026
Match List I with List II.

List I List II
(a) Isothermal (i) Pressure constant
(b) Isochoric (ii) Temperature constant
(c) Adiabatic (iii) Volume constant
(d) Isobaric (iv) Heat content is constant

Choose the correct answer from the options given below :
1.
(a) - (ii), (b) - (iii), (c) - (iv), (d) - (i)
2.
(a) - (ii), (b) - (iv), (c) - (iii), (d) - (i)
3.
(a) - (iii), (b) - (ii), (c) - (i), (d) - (iv)
4.
(a) - (i), (b) - (iii), (c) - (ii), (d) - (iv)
2021 Q297 JEE Mains MCQ
10 Mar 2026
n mole of a perfect gas undergoes a cyclic process ABCA (see figure) consisting of the following processes.

A $ \to $ B : Isothermal expansion at temperature T so that the volume is doubled from V1 to V2 = 2V1 and pressure charges from P1 to P2

B $ \to $ C : Isobaric compression at pressure P2 to initial volume V1.

C $ \to $ A : Isochoric change leading to change of pressure from P2 to P1.

Total workdone in the complete cycle ABCA is :

JEE Main 2021 (Online) 24th February Morning Shift Physics - Heat and Thermodynamics Question 313 English
A.
nRTln 2
B.
0
C.
$nRT\left( {\ln 2 - {1 \over 2}} \right)$
D.
$nRT\left( {\ln 2 + {1 \over 2}} \right)$
2021 Q298 JEE Mains MCQ
10 Mar 2026
Each side of a box made of metal sheet in cubic shape is 'a' at room temperature 'T', the coefficient of linear expansion of the metal sheet is '$\alpha$'. The metal sheet is heated uniformly, by a small temperature $\Delta$T, so that its new temperature is T + $\Delta$T. Calculate the increase in the volume of the metal box.
A.
3a3$\alpha$$\Delta$T
B.
4$\pi$a3$\alpha$$\Delta$T
C.
${{4 \over 3}}$$\pi$a3$\alpha$$\Delta$T
D.
4a3$\alpha$$\Delta$T
2021 Q299 JEE Mains Numerical
10 Mar 2026
The temperature of 3.00 mol of an ideal diatomic gas is increased by 40.0$^\circ$C without changing the pressure of the gas. The molecules in the gas rotate but do not oscillate. If the ratio of change in internal energy of the gas to the amount of workdone by the gas is ${x \over {10}}$. Then the value of x (round off to the nearest integer) is ___________. (Given R = 8.31 J mol$-$1 K$-$1)
2021 Q300 JEE Mains Numerical
10 Mar 2026
The average translational kinetic energy of N2 gas molecules at .............$^\circ$C becomes equal to the K.E. of an electron accelerated from rest through a potential difference of 0.1 volt. (Given kB = 1.38 $\times$ 10$-$23 J/K) (Fill the nearest integer).