Heat and Thermodynamics PYQs - Last 10 Years

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Practice 422 JEE Main Physics questions from Heat and Thermodynamics. Use the year-wise and type-wise breakdown to prioritize recent PYQs, then continue into the question list below.

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Last 10 Years Heat and Thermodynamics Questions

Showing 50 of 422 filtered questions.

1Heat And Thermodynamics

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) :

2Heat And Thermodynamics

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)

3Heat And Thermodynamics

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) :

4Heat And Thermodynamics

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 :

5Heat And Thermodynamics

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 tempe...

6Heat And Thermodynamics

A polyatomic ideal gas has 24 vibrational modes. What is the value of \(\gamma\)?

7Heat And Thermodynamics

Two identical metal wires of thermal conductivities K1 and K2 respectively are connected in series. The effective thermal conductivity of the combination is :

8Heat And Thermodynamics

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 :

9Heat And Thermodynamics

Which one is the correct option for the two different thermodynamic processes?

10Heat And Thermodynamics

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 :

11Heat And Thermodynamics

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 :

12Heat And Thermodynamics

In thermodynamics, heat and work are :

13Heat And Thermodynamics

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)

14Heat And Thermodynamics

For an ideal heat engine, the temperature of the source is 127\(^\circ\)C. In order to have 60% efficiency the temperature of the sink should be ___________\(^\circ\)C. (Round off to the Nearest Integer)

INTEGER+4 / -12021

15Heat And Thermodynamics

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 :

16Heat And Thermodynamics

Consider two ideal diatomic gases A and B at
some temperature T. Molecules of the gas A are
rigid, and have a mass m. Molecules of the gas
B have an additional vibrational mode, and
have a mass \({m \over 4}\)
. The ratio of the specific he...

17Heat And Thermodynamics

Which of the following is an equivalent cyclic
process corresponding to the thermodynamic cyclic
given in the figure ? where, 1 \(\to\) 2 is adiabatic.
(Graphs are schematic and are not to scale)

18Heat And Thermodynamics

Two gases-argon (atomic radius 0.07 nm,
atomic weight 40) and xenon (atomic radius
0.1 nm, atomic weight 140) have the same
number density and are at the same
temperature. The raito of their respective mean
free times is closest to :

19Heat And Thermodynamics

Starting at temperature 300 K, one mole of an
ideal diatomic gas (\(\gamma\) = 1.4) is first compressed
adiabatically from volume V1 to V2 = \({{{V_1}} \over {16}}\). It is
then allowed to expand isobarically to volume
2V2. If all the proc...

INTEGER+4 / -02020

20Heat And Thermodynamics

A thermodynamic cycle xyzx is shown on a V-T diagram.

The P-V diagram that best describes this cycle
is : (Diagrams are schematic and not to scale)

21Heat And Thermodynamics

The plot that depicts the behavior of the mean
free time t (time between two successive
collisions) for the molecules of an ideal gas, as
a function of temperature (T), qualitatively, is:
(Graphs are schematic and not drawn to scale)

22Heat And Thermodynamics

Consider a mixture of n moles of helium gas
and 2n moles of oxygen gas (molecules taken
to be rigid) as an ideal gas. Its CP/CV value
will be :

23Heat And Thermodynamics

A carnot engine having an efficiency of \({1 \over {10}}\) is
being used as a refrigerator. If the work done
on the refrigerator is 10 J, the amount of
heat absorbed from the reservoir at lower
temperature is :

24Heat And Thermodynamics

Three containers C1, C2 and C3 have water at
different temperatures. The table below shows
the final temperature T when different amounts
of water (given in litres) are taken from each
containers and mixed (assume no loss of heat
during the...

INTEGER+4 / -02020

25Heat And Thermodynamics

A litre of dry air at STP expands adiabatically to a volume of 3 litres. If \(\gamma\) = 1.40, the work done by air is : (31.4 = 4.6555) [Take air to be an ideal gas]

26Heat And Thermodynamics

A non-isotropic solid metal cube has coefficients of linear expansion as : 5 \(\times\) 10-5/oC along the x-axis and 5 \(\times\) 10-6/oC along the y and the z-axis. If the coefficient of volume expansion of the solid is C \(\times\) ...

INTEGER+4 / -02020

27Heat And Thermodynamics

Two moles of an ideal gas with \({{{C_P}} \over {{C_V}}} = {5 \over 3}\)
are mixed with 3 moles of another ideal gas
with \({{{C_P}} \over {{C_V}}} = {4 \over 3}\). The value of \({{{C_P}} \over {{C_V}}}\) for the
mixture is :

28Heat And Thermodynamics

A Carnot engine operates between two reservoirs of temperatures 900 K and 300 K. The engine
performs 1200 J of work per cycle. The heat energy (in J) delivered by the engine to the low
temperature reservoir, in a cycle, is _______.

INTEGER+4 / -02020

29Heat And Thermodynamics

Under an adiabatic process, the volume of an ideal gas gets doubled. Consequently the mean
collision time between the gas molecule changes from \({\tau _1}\)
to \({\tau _2}\)
. If \({{{C_p}} \over {{C_v}}} = \gamma\) for this gas then a g...

30Heat And Thermodynamics

M grams of steam at 100oC is mixed with 200 g of ice at its melting point in a thermally insulated
container. If it produced liquid water at 40oC [heat of vaporization of water is 540 cal/g and heat
of fusion of ice is 80 cal/g] the value o...

INTEGER+4 / -02020

31Heat And Thermodynamics

Two ideal Carnot engines operate in cascade (all heat given up by one engine is used by the other
engine to produce work) between temperature, T1
and T2
. The temperature of the hot reservoir of
the first engine is T1
and the temperature ...

32Heat And Thermodynamics

Molecules of an ideal gas are known to have three translational degrees of freedom and two
rotational degrees of freedom.The gas is maintained at a temperature of T. The total internal
energy, U of a mole of this gas, and the value of $$\ga...

33Heat And Thermodynamics

Initially a gas of diatomic molecules is contained in a cylinder of volume V1
at a pressure P1
and
temperature 250 K. Assuming that 25% of the molecules get dissociated causing a change in
number of moles. The pressure of the resulting ga...

INTEGER+4 / -02020

34Heat And Thermodynamics

In a dilute gas at pressure P and temperature T, the mean time between successive collisions of a
molecule varies with T as :

35Heat And Thermodynamics

An engine operates by taking a monoatomic ideal gas through the cycle shown in the figure. The
percentage efficiency of the engine is close to __________.

INTEGER+4 / -02020

36Heat And Thermodynamics

Three rods of identical cross-section and lengths are made of three different materials of thermal
conductivity K1
, K2
and K3
, respecrtively. They are joined together at their ends to make a long rod
(see figure). One end of the long rod...

37Heat And Thermodynamics

A bullet of mass 5 g, travelling with a speed of
210 m/s, strikes a fixed wooden target. One half
of its kinetic energy is converted into heat in
the bullet while the other half is converted into
heat in the wood. The rise of temperature of...

38Heat And Thermodynamics

Number of molecules in a volume of 4 cm3 of
a perfect monoatomic gas at some temperature
T and at a pressure of 2 cm of mercury is close
to? (Given, mean kinetic energy of a molecule
(at T) is 4 \(\times\) 10–14 erg, g = 980 cm/s2, densit...

39Heat And Thermodynamics

Three different processes that can occur in an
ideal monoatomic gas are shown in the P vs V
diagram. The paths are labelled as A \(\to\) B,
A \(\to\) C and A \(\to\) D. The change in internal
energies during these process are taken as...

40Heat And Thermodynamics

In an adiabatic process, the density of a
diatomic gas becomes 32 times its initial value.
The final pressure of the gas is found to be n
times the initial pressure. The value of n is :

41Heat And Thermodynamics

Nitrogen gas is at 300oC temperature. The
temperature (in K) at which the rms speed of a
H2 molecule would be equal to the rms speed
of a nitrogen molecule, is _______.
(Molar mass of N2 gas 28 g).

INTEGER+4 / -02020

42Heat And Thermodynamics

Two different wires having lengths L1 and L2,
and respective temperature coefficient of linear
expansion \(\alpha\)1 and \(\alpha\)2, are joined end-to-end.
Then the effective temperature coefficient of
linear expansion is :

43Heat And Thermodynamics

A closed vessel contains 0.1 mole of a monoatomic ideal gas at 200 K. If 0.05 mole of the same gas
at 400 K is added to it, the final equilibrium temperature (in K) of the gas in the vessel will be close
to _______.

INTEGER+4 / -02020

44Heat And Thermodynamics

Match the \({{{C_P}} \over {{C_V}}}\) ratio for ideal gases with different type of molecules :

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45Heat And Thermodynamics

The specific heat of water = 4200 J kg-1K-1 and the latent heat of ice = 3.4 \(\times\) 105 J kg–1. 100 grams of ice at 0oC is placed in 200 g of water at 25oC. The amount of ice that will melt as the temperature of water reaches 0oC is c...

46Heat And Thermodynamics

Match the thermodynamic processes taking place in a system with the correct conditions. In the
table : \(\Delta\)Q is the heat supplied, \(\Delta\)W is the work done and \(\Delta\)U is change in internal energy of the
system.

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47Heat And Thermodynamics

The change in the magnitude of the volume of an ideal gas when a small additional pressure \(\Delta\)P is
applied at a constant temperature, is the same as the change when the temperature is reduced by
a small quantity \(\Delta\)T at cons...

INTEGER+4 / -02020

48Heat And Thermodynamics

A bakelite beaker has volume capacity of 500 cc at 30oC. When it is partially filled with Vm
volume
(at 30oC) of mercury, it is found that the unfilled volume of the beaker remains constant as
temperature is varied. If \(\gamma\)(beaker) ...

INTEGER+4 / -02020

49Heat And Thermodynamics

Consider a gas of triatomic molecules. The
molecules are assumed to be triangular and
made of massless rigid rods whose vertices
are occupied by atoms. The internal energy of
a mole of the gas at temperature T is :

50Heat And Thermodynamics

A balloon filled with helium (32oC and 1.7 atm.)
bursts. Immediately afterwards the expansion
of helium can be considered as