Jr|11th IIT-JEE-MAIN|NEET|PHYSICS:VOL-IV

8. A man of 60 kg gains 1000 cal of heat by

eating 5 mangoes. His efficiency is 56%. To
what height he can jump by using this energy?
Joule’s law 1) 4m 2) 20 m 3) 28 m 4) 0.2 m

1. A piece of lead falls from a height of 100m on First law of thermodynamics

a fixed non-conducting slab which brings it to 9. How much work to be done in decreasing the
rest. If the specific heat of lead is 30.6 cal/kg volume of an ideal gas by an amount of
°C, the increase in temperature of the slab 2.4 x 10–4 m3 at constant normal pressure of
immediately after collision 1 x 105 N/m2
1) 6.72°C 2) 7.62°C 3) 5.62°C 4) 8.72°C 1) 28 joule 2) 27 joule 3) 24 joule 4)25joule
2. Hailstones fall from a certain height. If only 10. Find the external work done by the system in
1% of the hailstones melt on reaching the kcal, when 20 kcal of heat is supplied to the
ground, find the height from which they fall. system and the increase in the internal energy
(g = 10 ms -2 . L = 80 calorie/g and is 8400 J (J=4200J/kcal)
J = 4.2J/calorie) 1) 16 kcal 2) 18 kcal3) 20 kcal 4)19 kcal
1) 336 m 2) 236 m 3) 436 m 4) 536 m 11 Heat of 30 kcal is supplied to a system and
3. From what minimum height a block of ice has 4200 J of external work is done on the system
to be dropped in order that it may melt so that its volume decreases at constant
completely on hitting the ground pressure. What is the change in its internal
energy. (J = 4200 J/kcal)
mgh JL J 1) 1.302 x 105 J 2) 2.302 x 105 J
1) mgh 2) 3) 4) 3) 3.302 x 105 J 4) 4.302 x 105 J
J g Lg
12. Air expands from 5 litres to 10 litres at 2 atm
4. Two spheres A and B with masses in the ratio pressure. External workdone is
2 : 3 and specific heat 2 : 3 fall freely from 1) 10J 2) 1000J 3) 3000 J 4) 300 J
rest. If the rise in their temperatures on
13. Heat given to a system is 35 joules and work
reaching the ground are in the ratio 1 : 2 the
done by the system is 15 joules. The change
ratio of their heights of fall is
in the internal energy of the system will be
1) 3 : 1 2) 1 : 3 3) 4 : 3 4) 3 : 4
1) – 50 J 2) 20 J 3) 30 J 4) 50 J
5. From what height a block of ice must fall into
14. A gas is compressed at a constant pressure of
1 50 N/m2 from a volume 10m3 to a volume of
a well so that th of its mass may be melted
100 4m3. 100J of heat is added to the gas then its
(g = 10 m/s2) internal energy
1) 300 m 2) 336 m 3) 660 m 4) none 1) Increases by 400J 2) Increases by 200J
6. Two identical balls ‘A’ and ‘B’ are moving with 3) Decreases by 400J 4) Decreases by 200J
same velocity. If velocity of ‘A’ is reduced to
half and of ‘B’ to zero, then the raise in CP, CV and their relations
temperatures of ‘A’ to that of ‘B’ is 15. Find the change in internal energy in joule.
1) 3 : 4 2) 4 : 1 3) 2 : 1 4) 1 : 1 When 10g of air is heated from 30°C to 40°C
7. A 50kg man is running at a speed of 18kmh 1 . (c = 0.172 kcal/kg K, J = 4200 J/kcal)
v
If all the kinetic energy of the man can be used 1) 62.24 J 2)72.24 J3)52.24 J 4)82.24 J
to increase the temperature of water from 16. The temperature of 5 moles of a gas at
200 C to 300 C , how much water can be heated constant volume is changed from 1000C to
with this energy? 1200C. The change in internal energy is 80J.
1) 15 g 2) 20 g 3) 30 g 4) 40 g The total heat capacity of the gas at constant
THERMODYNAMICS 93
 Jr|11th IIT-JEE-MAIN|NEET|PHYSICS:VOL-IV
volume will be in joule/kelvin is change is (2008 M)
1) 8 2) 4 3) 0.8 4) 0.4 1) RT log4 2) RT log2 3) RT log1 4) RT log3
17. When an ideal diatomic gas is heated at 24. One mole of O2 gas having a volume equal to
constant pressure, the fraction of heat energy 22.4 litres at 00C and 1 atmospheric pressure
supplied which is used in doing work to is compressed isothermally so that its volume
maintain pressure constant is reduces to 11.2 litres. The work done in this
1) 5/7 2) 7/2 3) 2/7 4) 2/5 process is
18. When a monoatomic gas expands at constant 1)1672.5J 2)1728J 3) –1728J 4) –1572.5J
pressure, the percentage of heat supplied that 25. The isothermal Bulk modulus of an ideal gas
increases temperature of the gas and in doing at pressure P is
external work in expansion at constant 1) P 2) P 3) P/2 4) P / 
pressure is
26. Diatomic gas at pressure ‘P’ and volume ‘V’
1) 100%, 0 2) 60%, 40%
is compressed adiabatically to 1/32 times the
3) 40%, 60% 4) 75%, 25% original volume. Then the final pressure is
19. For a gas, the difference between the two 1) P/32 2) 32 P 3) 128 P 4) P / 128
specific heats is 4150J Kg-1 K-1 and the ratio 27. The pressure and density of a diatomic gas
of specific heats is 1.4. What is the specific
heat of the gas at constant volume in    7 / 5 change adiabatically from (P, d) to
J Kg-1 K-1? d1 P1
(P1, d1). If  32 , then should be
1)8475 2) 5186 3)1660 4) 10375 d P
20. The specific heat of air at constant pressure 1) 1/128 2) 32
is 1.005 kJ/kg K and the specific heat of air at 3) 128 4) none of the above
constant volume is 0.718 kJ/kgK. Find the
28. An ideal gas at a pressure of 1 atmosphere
specific gas constant.
and temperature of 270C is compressed
1) 0.287 kJ/kg K 2) 0.21 kJ/kg K adiabatically until its pressure becomes 8
3) 0.34 kJ/kg K 4) 0.19 kJ/kg K times the initial pressure, then the final
21. The specific heat of Argon at constant volume
temperature is    3 / 2 
is 0.3122kJ/kg K. Find the specific heat of
Argon at constant pressure if R = 8.314 kJ/k 1) 6270 C 2) 5270C 3) 4270C 4) 3270C
mole K. (Molecular weight of argon = 39.95) 29. The volume of a gas is reduced adiabatically
1) 5203 2) 5302 3) 2305 4) 3025 1
to of its volume at 270C, if the value of
22. If the ratio of the specific heats of steam is 4
1.33 and R = 8312J/k mole K find the molar   1.4, then the new temperature will be
heat capacities of steam at constant pressure 1) 350 x 40.4K 2) 300 x 40.4K
and constant volume. 3) 150 x 40.4K 4) None of these
1) 33.5 kJ/k mole, 25.19 kJ /kg K 30. Two moles of an ideal monoatomic gas at 270C
2) 25.19 kJ/k mole, 33.5 kJ/kg K occupies a volume of V. If the gas is expanded
3) 18.82 kJ/k mole, 10.82 kJ/k mole adiabatically to the volume 2V, then the work
4) 24.12 kJ /k mole, 16.12 kJ/k mole done by the gas will be   5 / 3
Different thermodynamic process 1) –2767.23J 2) 2767.23J
23. One mole of an ideal gas undergoes an 3) 2500J 4) –2500J
isothermal change at temperature 'T' so that 31. A container of volume 1m3 is divided into two
its volume V is doubled. R is the molar gas equal compartments, one of which contains an
constant. Work done by the gas during this ideal gas at 300 K. The other compartment is
vacuum. The whole system is thermally isolated
94 THERMODYNAMICS
Jr|11th IIT-JEE-MAIN|NEET|PHYSICS:VOL-IV
from its surroundings. The partition is removed
3) 8.6  103 0C 4) 9.6 103 0C
and the gas expands to occupy the whole volume
of the container. Its temperature now would be 2. A steel ball of mass 0.1kg falls freely from a
1) 300 K 2) 250 K 3) 200 K 4) 100 K height of 10m and bounces to a height of 5.4m
32. A gas at 10 C temperature and 1.013×105 Pa
o from the ground. If the dissipated energy in
pressure is compressed adiabatically to half this process is absorbed by the ball, the rise
of its volume. If the ratio of specific heats of in its temperature is (specific heat of steel
the gas is 1.4, what is its final temperature? 460 Jkg 1 K 1 , g  10ms 2 )
1) 103oC 2) 123oC 3) 93oC 4) 146oC
1) 0.01 0C 2) 0.1 0C 3) 1 0C 4) 1.1 0C
33. Find the work done by a gas when it expands
isothermally at 37oC to four times its initial volume. 3. A lead bullet (specific heat =
1) 3753J 2) 3573J 3) 7533J 4) 5375J 0.032cal / gm 0C ) is completely stopped
when it strikes a target with a velocity of
Heat engine
300m/s. The heat generated is equally shared
34. The efficiency of a heat engine if the by the bullet and the target. The rise in
temperature of source 227oC and that of sink temperature of bullet will be
is 27oC nearly
1) 16.7 0 C 2) 1.67 0 C 3) 167.40 C 4) 267.40 C
1) 0.4 2) 0.5 3) 0.6 4) 0.7
4. A block of ice falls from certain height and
35. A Carnot engine takes 3  106 cal. of heat from completely melts. If only 3/4th of the energy
a reservoir at 6270C, and gives it to a sink at is absorbed by the block, the height of the
270c. The work done by the engine is
fall should be  L  363SI unitsand g 10ms2 
1) 4.2  106 J 2) 8.4  106 J 3) 16.8  106 J 4) zero
1) 48.4m 2) 84.4m 3) 88.4m 4) 44.8m
5. A lead bullet of mass 21g travelling at a speed
of 100 ms 1 comes to rest in a wooden block.
1) 2 2) 1 3) 3 4) 2 5) 2 6) 1 If no heat is taken away by the wood, the rise
7) 1 8) 1 9) 3 10)2 11) 1 12)2 in temperature of the bullet in the wood nearly
13)2 14)1 15)2 16)2 17)3 18)2 is (Sp. heat of lead 80cal/kg 0 C )
19)4 20)1 21) 1 22)1 23)2 24)4
1) 250 C 2) 280 C 3) 330 C 4) 150 C
25)1 26)3 27)3 28)4 29)2 30)2
31)1 32)1 33)2 34) 1 35) 2 First law of thermodynamics
6. When 20J of work was done on a gas, 40J of
heat energy was released. If the initial
internal energy of the gas was 70J, what is
the final internal energy?
Joule’s law 1) 50J 2) 60J 3) 90J 4) 110J
1. A copper block of mass 1kg slides down on a CP,CV and their relations
rough inclined plane of inclination 370 at a 7. A quantity of heat ‘Q’ is supplied to a
constant speed. Find the increase in the monoatomic ideal gas which expands at
temperature of the block as it slides down constant pressure. The fraction of heat that
through 60cm assuming that the loss in goes into workdone by the gas is
mechanical energy goes into the copper block 1) 2/5 2) 3/5 3) 2/3 4) 1
as thermal energy. (specific heat of copper =
8. For hydrogen gas C p  Cv  a and for Oxygen
420 Jkg 1 K 1 , g  10ms 2 )
gas C p  Cv  b , where C p and Cv are molar
1) 6.6  103 0C 2) 7.6  103 0C
THERMODYNAMICS 95
 Jr|11th IIT-JEE-MAIN|NEET|PHYSICS:VOL-IV
specific heats. Then the relation between ‘a’
and ‘b’ is
16. One mole of an ideal gas   7 / 5  is
adiabatically compressed so that its
1) a=16b 2) b=16a 3) a=4b 4) a=b
9. H calories of heat is required to increase temperature rises from 27 0 C to 350 C . The
temperature of one mole of monoatomic gas work done by the gas is (R=8.47J/mol-K)
from 200 C to 300 C at constant volume. The 1)-160J 2)-168J 3)150J 4)120J
quantity of heat required to increase the 17. The tyre of a motor car contains air at 150 C if
temperature of 2 moles of a diatomic gas from the temperature increases to 35 0C, the
200 C to 250 C at constant volume is approximate percentage increase in pressure
is (ignore the expansion of tyre)
4H 5H 7H
1) 2) 3) 2H 4) 1) 7 2) 9 3) 11 4) 13
3 3 3
18. A given mass of a gas is compressed
10. 1/2 mole of Helium gas is contained in a isothermally until its pressure is doubled. It is
container at S.T.P. The heat energy needed to then allowed to expand adiabatically until its
double the pressure of the gas, keeping the original volume is restored and its pressure is
volume constant (heat capacity of the then found to be 0.75 of its initial pressure.
gas= 3 Jg  1 K  1 ) The ratio of the specific heats of the gas is
1) 3276J 2) 1638J 3) 819J 4) 409.5J approximately
11. How much heat energy in joules must be 1) 1.20 2) 1.41 3) 1.67 4) 1.83
supplied to 14gms of nitrogen at room 19. One mole of oxygen is heated at constant
temperature to raise its temperature by 40 C pressure starting at 00 C . The heat energy
at constant pressure? (Mol.wt.of N 2 =28gm, that must be supplied to the gas to double its
volume (R is the molar gas constant)
R=constant)
1) 50R 2) 60R 3) 70R 4) 80R 1) 2.5  273  R 2) 3.5  273  R
12. The volume of 1kg of hydrogen gas at N.T.P. 3) 2.5  546  R 4) 3.5  546  R
is 11.2 m3 . Specific heat of hydrogen at 20. The equation of a certain gas can be written
constant volume is 100.46J kg 1K 1 . Find the
T7 / 5
specific heat at constant pressure in J kg 1 K 1 . as 2 / 5  cons tan t . Its specific heat at
P
1) 120.2 2) 142.2 3) 163.4 4)182.3
constant volume will be
13. 3 moles of a monoatomic gas requires 60cal
heat for 50 C rise of temperature at constant 3 5 7
1) R 2) R 3) R 4) 2R
volume, then heat required for 5 moles of 2 2 2
same gas under constant pressure for 100 C
rise of temperature is (R=2 cal/mole-k) Heat engine
1) 200cal 2) 400cal 3) 100cal 4) 300cal 21. In a mechanical refrigerator, the low
14. One mole of a monoatomic gas is mixed with temperature coils are at a temperature of
one mole of a diatomic gas. What will be the 230 C and the compressed gas in the
value of  . condenser has a temperature of 27 0 C . The
1) 1.5 2) 1.54 3) 1.4 4) 1.45 theoretical coefficient of performance is
Different thermodynamic process 1) 5 2) 8 3) 6 4) 6.5
22. A Carnot’s engine whose sink is at a
15. The triatomic gas is heated isothermally. What
temperature of 300K has an efficiency of 40%.
percentage of the heat energy is used to
By how much should the temperature of the
increase the internal energy
source be increased so as to increase the
1) 0% 2) 14% 3) 60% 4) 100% efficiency to 60%.
96 THERMODYNAMICS
Jr|11th IIT-JEE-MAIN|NEET|PHYSICS:VOL-IV
1) 250K 2) 275K 3) 300K 4) 325K water be raised by doing 4200 J of work in
23. A refrigerator placed in a room at 300K has stirring the water?
inside temperature 200K. How many calories 1) 0.010c 2) 0.10c 3) 10c 4) 100c
of heat shall be delivered to the room for each 3. A lead ball moving with a velocity v strikes a
2KiloCal of energy consumed by the wall and stops. If 50% of its energy is
refrigerator ideally converted into heat, The increase in
1) 4K.cal 2) 2K.cal 3) 8K.cal 4) 6Kcal temperature is (Specific heat of lead is S)
24. An ideal Carnot’s engine whose efficiency is 1) 2v2 / JS 2)v2 / 4JS3) v2 S/ J 4) v2 S/ 2J
40% receives heat at 500K. If the efficiency is 4. A steel drill is making 180 revolutions per
to be 50% then the temperature of sink will be minute, under a constant torque of 5 N-m. If it
1) 600K 2) 800K 3)1000K 4) 250K drills a hole in 7 sec in a steel block of mass
25. Two Carnot engines A and B are operated in 600 gm, rise in temperature of the block is
succession. The first one, A receives heat from (S = 0.1 cal gm-1 0C-1)
a source at T1=800Kand rejects to a sink at 1) 2.6ºC 2) 1.3ºC 3) 5.2ºC 4) 3ºC
T2K. The second engine B receives heat 5. The time taken by an electric heater to rise
rejected by the first engine and rejects to the temperature of 100 cc of water through
another sink at T3=300K. If the efficiencies of 100C is 7s. If there is no loss in energy, power
two engines are equal, then the value of T2 is
of that motor is  J  4.2 J / cal 
1) 489.4K 2) 469.4K 3) 449.4K 4) 429.4K
26. A freezer has coefficient of performance 5. 1) 420 W 2) 42 W 3) 4.2 W 4) 0.6 W
When 3.6 x 106 J work is done on the freezer,
First law of thermodynamics
what mass of water at 00C is converted into
ice cubes at 00C 6. When 1 gm of water changes from liquid to
1)  5 kg 2)  3.6 kg 3)  54 kg 4)  107 kg vapour phase at constant pressure of 1
atmosphere, the volume increases from 1cc
to 1671cc. The heat of vaporisation at this
pressure is 540 cal/gm. Increase in internal
energy of water is
1) 3 2) 2 3) 3 4) 1
(1 atmosphere = 1.01 x 106 dyne/cm2)
5) 4 6) 1 7) 1 8) 4
1) 4200J 2) 8200J 3) 1200J 4) 2100 J
9) 2 10) 2 11) 3 12) 2
13) 4 14) 1 15) 1 16) 2 7. One cubic meter of an ideal gas is at a pressure
17) 1 18) 2 19) 2 20) 2 of 105 N / m 2 and temperature 300K. The gas
21) 1 22) 1 23) 4 24) 4 is allowed to expand at constant pressure to
25) 1 26) 3 twice its volume by supplying heat. If the
change in internal energy in this process is
10 4 J, then the heat supplied is
1) 105 J 2) 10 4 J 3) 11 104 J 4) 2.2 105 J
8. When unit mass of water boils to become
Joule's law steam at 1000C, it absorbs Q amount of heat.
1. An ice block is projected vertically up with a The densities of water and steam at 1000C are
velocity 20 ms-1. The amount of ice that melt 1 and  2 respectively and the atmospherec
when it reaches the ground if the mass of ice pressure is P0. The increae in internal energy
block is 4.2 kg. of the wter is
1) 2.5 gm 2) 2.5 kg 3) 0.25 kg 4) 0.25 gm
2. How much will the temperature of 100g of

THERMODYNAMICS 97
 Jr|11th IIT-JEE-MAIN|NEET|PHYSICS:VOL-IV

1 1 CP, CV and their relations

1)Q 2) Q  P0      12. A cylinder of fixed capacity 67.2 litres
 1 2 
contains helium gas at S.T.P. The amount of
 1 1 1 1 heat required to raise the temperature of
3) Q  P0      4) Q  P0      the gas by 150C is (R =8.31 J mol-1k-1)
 2 1   1 2 
1) 520 J 2) 560.9 J 3) 620 J 4) 621.2 J
9. Consider the melting of 1g of ice at 00C to water 13. 14 g of N2 gas is heated in a closed rigid
at 00C atmospheric pressure. Then the change container to increase its temperature from
in internal energy of the system (density of 230C to 430C. The amount of heat supplied to
ice is 920kg/m3) the gas is
1) 334 J 2) 420 J 3) 540 J 4) 680 J
1) 25 cal 2) 50 cal 3) 100 cal 4) 30 cal
10. The equation of state for a gas is given by
14. 70 cal of heat is required to raise the temperature
PV=nRT+  V, where n is the number of moles
of 2 moles of an ideal gas at constant pressure
and  is a positive constant. The intial
from 30ºC to 35ºC. What is the amount of heat
temperature and pressure of one mole of the
required to rise the temperature of same gas
gas contained in a cylinder are T0 and P0
through the same range at constant volume?(R
respectively. The work done by the gas when
= 2cal mole-1K-1)
its temperature doubles isobarically will be
(Mains 2014) 1) 28 J 2) 50 Cal 3) 75 J 4) Zero
15. The relation between internal energy U,
P0T0 R P0T0 R pressure P and volume V of a gas in an
1) P   2) P  
0 0 adiabatic process is : U  a  bPV Where ‘a’
3) P0 T0 RIn2 4) P0 T0 R and ‘b’ are constants. What is the value of the
ratio of the specific heats?
11. An ideal monatomic gas is confined in a
cylindrical by a spring loaded piston of cross a b 1 a 1 b
1) 2) 3) 4)
section 8.0 x 10-3m2. Initially the gas is at b b a a
300K and occupies a volume of 2.4 x 10-3m3 16. The ratio of specific heats of a gas is  . The
and the springs is in its relaxed state as shown change in internal energy of one mole of gas
in figure. The gas is heated by a small heater when the volume changes from V to 2V at
untill the piston moves out slowly by 0.1 m. constant pressure “P” is
The cylinder and the piston are thermally
PV PV
insulated. The piston and spring are massless 1)   1 2) PV 3)   1 4) 
and there is no friction between the position
and the cylinder. The final temperature of th Different thermodynamic process
gass will be (Mains 2014)
17.  for a gas is 5/3. An ideal gas at 270C is
(Neglect the heat loss through the load wires
compressed adiabatically to 8/27 of its original
of the heater. The heat capacity of the heater
volume. The rise in temperature of the gas is
coil is also negligible)
1) 4500C 2) 3750C 3) 2250C 4) 4020C
18. One mole of a gas expands with temperature
T such that its volume, V = kT2, where k is a
constant. If the temperature of the gas
changes by 600C then the work done by the
gas is
1) 120 R 2) R ln 60 3) kR ln 60 4) 60 kR
1) 300K 2) 800K 3) 500K 4) 1000K
19. A monoatomic ideal gas, initially at temperature

98 THERMODYNAMICS
Jr|11th IIT-JEE-MAIN|NEET|PHYSICS:VOL-IV

T1, is enclosed in a cylinder fitted with a 2 3

frictionless piston. The gas is allowed to expand 1) P 2) P 3) P 4) 2P
3 2
adiabatically to a temperature T2 by releasing
the piston suddenly. If L1 and L2 are the lengths 25. An ideal gas is taken through a cyclic thermo
of the gas column before and after expansion dynamical process through four steps. The
respectively, then T1/T2 is given by amounts of heat involved in these steps are :
2 2
Q1  5960 J , Q2  5585 J , Q3  2980 J , Q4  3645 J ;
 L1  3 L1 L2 L2  3
1)   2) L 3) L 4)  
respectively, The corresponding works
 L2  2 1  L1 
involved are W1  2200 J , W2  825 J ,W3  1100 J
20. Three samples of the same gas x , y and z , for and W4 respectively. Find The value of W4
which the ratio of specific heats is  =3/2, have
and efficiency of the cycle:
initially the same volume. The volumes of each
sample is doubled , by isobaric process in the 1) 1315 J, 10% 2) 275 J, 11%
case of y and by isothermal process in the case 3) 765 J, 10.82% 4) 675 J , 10.82%
of z. If the initial pressures of the samples x,y 26. During an adiabatic compresssion, 830 J of
and z are in the ratio 2 2 : 1 : 2 , then the ratio work is done on 2 moles of a diatomic ideal
gas to reduce its volume by 50%. The change
of their final pressures is
in its temperature is nearly
1) 2 : 1 : 1 2) 1 : 1 : 1 3) 1 : 2 : 1 4) 1 : 1 : 2
(R=8.3JK-mol-1) (Mains 2014)
21. n moles of an ideal gas undergo a process in
1) 40 K 2) 33K 3) 20K 4) 14K
which the temperature changes with volume
as T = kV2. The work done by the gas as the 27. Consider a spherical shell of radius R at
temperature T. The black body radiation
temperature changes from T0 to 4T0 is inside it can be considered as an ideal gas of
photons with internal energy per unit volume
5 3
1) 3nRT0 2)   nRT0 3)   nRT0 4) Zero 1 U 
2
  2 U
u  T 4 and pressure p    . If the
22. 'm' grams of a gas of a molecular weight M is V 3 V 
flowing in an isolated tube with velocity 2v. If shell now undergoes an adiabatic expansion
the gas flow is suddenly stopped the rise in its the relation between T and T is (Mains 2015)
temperature is; (  = ratio of specific heats;
1 1
R = universal gas constant; J = Mechanical 1) T  e  R 2) T  e 3R 3) T  4) T  3
R R
equivalent of heat)
28. An ideal gas equation a quasistatic, reversible
2 Mv 2    1 mv 2    1 process in which its molar heat capacity C
1) 2)
RJ M 2 RJ remains constant. If during this process the
relation of pressure P and volume V is given
mv 2  Mv 2  by PVn = constant, then n is given by (Here
3) 4)
2 RJ 2 RJ CP and CV are molar specific heat at constant
23. Heat is supplied to a diatomic gas at constant pressure and constant volume, respectively)
pressure. The ratio of  Q:  U:  W is: (Mains 2016)
1)5 : 3 : 2 2) 5 : 2 : 3 3)7 : 5 : 2 4)7 : 2 : 5 CP C  CP
24. A given quantity of an ideal gas at pressure P 1) n  C 2) n  C  C
V V

and absolute temperature T obeys P  T 3

CP  C C  CV
during adiabatic process. The adiabatic bulk 3) n  C  C 4) n  C  C
modulus of the gas is V P

29. 'n' moles of an ideal gas undergoes a process

AB as shown in the figure. The maximum
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 Jr|11th IIT-JEE-MAIN|NEET|PHYSICS:VOL-IV

temperature of the gas during the process will 3  5 3  5 5  1

be(Mains 2016) 1) 2) 3) 4)
6 6 2 2
P 32. An ideal gas goes through a reversible cycle
a  b  c  d has the V-T diagrm shown
A below, process d  a and b  c aree adiabatic
2P0 V
c
P0 B b
d
a
V0 2V0 V T

9P0 V0 3P0 V0 9P0 V0 9P0 V0 The corresponding P-V diagram for the
1) 2) 3) 4) process is (all figures are schematic and not
4nR 2nR 2nR nR
drawn to scale)
30. One mole diatomic ideal gas undergoes a cyclic
process ABC as shown in the figure. The P P
process BC is adiabilitic. The temperature at a b d c
A, B and C are 400 K, 800K and 600K
respectively. Choose the correct statement 1) c 2) a b
d
(Mains 2014)
V V
B 800K P P
a b d c

3) c 4)
P d a b
600K
C V V
A
400K
Heat engine
V
33. A Carnot's engine is made to work between
1) The change in internal energy in whole cyclic 2000C and 00C first and then between 00C and
process is 250 R –2000C. the ratio of efficiencies of the engine
2) The change in internal energy in the process CA in the two cases is
is 700 R 1) 1.73:1 2) 1:1.73 3) 1:1 4) 1 : 2
3) The change in internal energy in the process AB 34. A scientist says that the efficiency of his heat
is -350 R engine which operates at source temperature
4) The change in internal energy in the process BC 1270C and sink temperature 270C is 26%, then
is -500 R 1) It is impossible
31. Consider an ideal gas confined in an isolated 2) It is possible but less probable
closed chamber. As the gas underogoes an 3) It is quite probable
adiabatic expansion, the average time of
4) Data is incomplete
collision between molecular increases as Vq,
where V is the volume of the gas. The value 35. Efficiency of a Carnot engine is 50% when
temperature of outlet is 500 K. In order to
 CP  increase efficiency up to 60% keeping
of q is :    C  (Mains 2015) temperature of intake the same what is
 V 
temperature of outlet
1) 200 K 2) 400 K 3) 600 K 4) 800 K

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Jr|11th IIT-JEE-MAIN|NEET|PHYSICS:VOL-IV
36. An ideal refrigerator has a freezer at a B(2P,V) C(2P,2V) 1) PV
temperature of –130C. The coefficient of
performance of the engine is 5. The P 2) 2PV
temperature of the air (to which heat is A(P,V) D(P,2V) 3) 3PV
rejected) will be
V 4) 4PV
1) 3250C 2) 325 K 3) 390C 4) 3200C
44. The figure shows P-V graph of an ideal one
37. The heat reservoir of an ideal Carnot engine
mole gas undergone to cyclic process ABCA,
is at 800 K and its sink is at 400 K. The amount
then the process B  C is
of heat taken in it in one second to produce
useful mechanical work at the rate of 750 J is 1) Isobaric
1)2250 J 2)1125 J 3)1500 J 4) 750 J 2P0 B

38. A Carnot engine works between 2000C and 00C. 2) Adiabatic

Another Carnot engine works between 00C and P
P0 A C 3) Isochoric
-2000C. In both cases the working substance
absorbs 4 kilocalories of heat from the source. V0 V 2V0 4) Isothermal
The efficiency of first engine will be 45. On a T-P diagram, two moles of ideal gas
perform process AB and CD. If the work done
100 200 173 273
1) 2) 3) 4) by the gas in the process AB is two times the
173 473 273 373 work done in the process CD then what is the
39. In the above problem, the output of second value of T1/T2?
engine is
T 1) 1/2
1) 29.3 103 Cal 2) 12.3  103 Cal A
T1
B 2) 1
3) 12.3  10 joule
3
4) 2.93 10 joule
3
T2 C
D 3) 2
40. In the above problem, the ratio of outputs of
two engines is P 4) 4
1) 0.577 2) 0.377 3) 0.777 4) 0.177 46. A Sample of ideal monoatomic gas is taken
41. A Carnot freezer takes heat from water at 00C round the cycle ABCA as shown in the figure.
inside it and rejects it to the room at a temperature The work done during the cycle is
of 270C. The latent heat of ice is 336 x 103 Jkg-1. B
IF 5 kg of water at 00C is converted into ice at (4P,3V) 1) Zero
00C by the freezer, then the energy consumed by
2) 3PV
the freezer is close to (Mains 2016)
1) 1.68 x 10 J6
2) 1.71 x 107J P A (P,V) C (P,3V) 3) 6PV
3) 1.51 x 105J 4) 1.67 x 105J
42. Carnot engine absorbs 1000 J of heat energy V 4) 9PV
from a reservoir at 1270C and rejects 600 J of 47. In the given elliptical P - V diagram
heat energy during each cycle. The efficiency
of engine and temperature of sink will be P2
(Mains 2016)
P1
1) 20% and -43 C 0
2) 40% and -330C
3) 50% and -200C 4) 70% and -100C
P
Graphs V1 V2
V
43. An ideal monoatomic gas is taken round the V
cycle ABCDA as shown in the diagram. The 1) The work done is positive
work done during the cycle is 2) The change in internal energy is non-zero

THERMODYNAMICS 101
 Jr|11th IIT-JEE-MAIN|NEET|PHYSICS:VOL-IV
T C
 
3) The work done =   4   P2  P1 V2  V1 
 
400 K B
4) The work done =  V2  V1 2    P2  P1  2
300 K A
48. A system changes from the state (p1,v1) to V
(p2,v2) as shown in the diagram. The workdone
by the system is. 1) -1531 J 2) -1631 J 3) -1731 J 4) -1831 J
52. An ideal gas is taken through A  B  C  A,
P2 ,V2 
5 as shown in figure. If the net heat supplied to
P 4 the gas in the cycle is 5J, the work done by
3 the gas in the process C  A is
10 Nm
5 2 2 P1,V1 
1
C B
2
1 2 3 4 5 3

V(m )
3
V(m )
1)12x104J 2)12x108J3)12x105J 4) 6x104 J
1 A
49. The heat energy absorbed by a system in going
through a cyclic process shown in figure is
-2
P(Nm ) 10
30
1) -5J 2) -10J 3) -15J 4) -20J
volume
(litres) 10

10 30
Pressure (KPa) 1) 1 2) 4 3) 2 4) 1 5) 4 6) 4
1) 103  J 2) 102  J 3) 104  J 4) 107  J 7) 3 8) 2 9) 1 10) 1 11) 2 12) 2
50. A thermodynamic system is taken through the 13) 2 14) 2 15) 2 16) 1 17) 2 18) 1
cycle PQRSP process. The net work done by 19) 4 20) 2 21) 3 22) 1 23) 3 24) 3
the system is 25) 3 26) 3 27) 3 28) 2 29) 1 30) 4
31) 3 32) 2 33) 2 34) 1 35) 2 36) 3
P
37) 3 38) 2 39) 3 40) 1 41) 4 42) 2
S
43) 1 44) 4 45) 3 46) 2 47) 3 48) 3
300kPa R
49) 2 50) 2 51) 4 52) 1

100kPa Q
P
100cc 300cc V
1) 20 J 2) – 40 J 3) 400 J 4) – 374 J
51. A cyclic process performed on one mole of an
ideal gas. A total 1000 J of heat is withdrawn
from the gas in a complete cycle. Find the work
done by the gas during the process B  C.

102 THERMODYNAMICS