SECTION 1 QUESTIONS
1. A balloon is just immersed below the water surface. As it is submerged through a little, it sinks because of
a) surface tension b) increase in hydrostatic pressure
c) decrease in hydrostatics pressure d) both hydrostatic pressure and surface tension 2. Two rain drops of same radius and of terminal velocity 1 m/s coalesce. The terminal velocity
of resulting drop is
a) 2 m/s b) 21/3 m/s c) 22/3 m/s d) √2 m/s 3. Coal tar is first heated and then spread. This is because of
a) decrease in surface tension with heating b) increase in surface tension in heating c) increase in viscosity on heating d) decrease in viscosity on heating
4. Some water and a mixture of alcohol and glycerine of same density are provided. Of the two a) water has greater surface tension and less viscosity
b) water has less surface tension and greater viscosity c) water has greater surface tension and less viscosity
d) water has same surface tension and same viscosity as that of mixture
5. Liquid rises to a height h in a capillary tube of cross sectional area A. In a capillary tube of area 2A it will rise to a height
a) 2
h b) 2h c)
2
h d) 2 h
6. In a capillary tube pure water rises to a height h. If warm water is used in the same capillary tube, the capillary rise
a) will be greater than h b) will be less than h
c) will be equal to h d) cannot be answered from the data 7. A liquid rises in a capillary tube to a height h. The capillary rise will be less in
a) a lift accelerating up b) at a place higher altitude c) all the two places above d) at centre of earth
8. The depression at the centre of a uniform metre scale when loaded is x. If the metre scale is cut into 2 half metre scales and one of them is used with the same load, the depression will be a) 2x b) 8x c)
4
x d)
8 x 9. Read the following statements:
2
Statement A: Addition of any impurity decreases surface tension of water Statement B: Surface tension of water decreases on heating. Of these statements
a) both A and B are correct b) both A and B are wrong c) A is correct, B is wrong d) A is wrong, B is correct
10. A piece of wood floats in a beaker of water at 00C in a surrounding temperature of 200 C. As water warms up to room temperature the immersed fraction of wood will
a) increase b) decrease
c) remain same d) first decrease and then increase
11. A metal rod of unit length and unit cross-sectional area is heated through 10C If Young’s modulus of elasticity is E and the linear expansivity α/0C, then the compressional force required to prevent the rod from expanding is
a) Eα b) α/E c) E/α d) 3Eα
12. Water is used to cool in radiators of engines in cars because
a) of its low density b) of its easy availability c) of its high specific heat d) of its low boiling point 13. When an ice melts at room temperature
a) the molecules gain kinetic energy b) the molecules lose potential energy c) the molecules gain potential energy d) the molecules lose kinetic energy 14. The coefficient of thermal conductivity of a metal plate depends on
a) temperature difference between the two sides b) thickness of the metal plate
c) area of cross section of the metal plate d) material of the plate
15. *The temperature of an isotropic cubical solid of length L, density d and coefficient of linear expansion α per degree kelvin, is raised by 100 C. Then at this temperature, to a good approximation its
a) length is L(1+10 α) b) total surface area is L2 (1+20α) c) density is d(1+30α) d) density is d/(1+30α)
16. 3.21 kg of ice at 00C is mixed with 3.21 kg of water at 69.80C. The temperature of the mixture is
a) 00C b) 17.90C c) 240C d) 34.90C
17. One mole of helium is mixed with one mol of hydrogen. The molar heat capacity at constant volume of the mixture is
a) 4.2 J mol-1K-1 b) 8.4 mol-1K-1 c) 12.6 mol-1K-1 d) 16.6 mol-1K-1
18. Sodium vapour lamp gives two bright yellow lines. If an arc source is placed behind sodium, we will get
a) the same two bright yellow lines, under dark background b) uniform illumination
c) two dark lines under bright background
d) the same two bright sodium lines under brighter background
19. 70 calories of heat are required to raise the temperature of 2 mol of an ideal gas at constant pressure from 300C to 350C. The amount of heat required (in calories) to raise the temeperature of the same gas through the same range (300C to 350C) at constant volume is a) 30 b) 50 c) 70 d) 90
20. An extremely hot star would look
a) violet or indigo b) green or yellow c) orange or red d) white
21. Thermal energy of air molecules at room temperature is of the order of
a) 0.2 eV b) 2 eV c) 0.02 eV d) 0.002 eV
22. The rms velocity of oxygen molecules at STP is V ms-1. If it is heated at a constant pressure until the volume becomes 4 times, the original volume, the new rms velocity will be
a) 4V b) 3V c) 2V d) V
23. A beaker full of water kept inside a room during acute winter overflows when heated. If it had been cooled from the room temperature, it would have over flown. The temperature of the room is (in 0C)
a) 1 b) 2 c) 3 d) 4
24. Two metallic spheres S1 and S2 are made of the same material and have identical surface finish. The mass of S1 is three times that of S2. Both the spheres are heated to the same high temperature and placed in the same room having lower temperature but are thermally insulated from each other. The ratio of the initial rate of cooling of S1 to that of S2
a) 31/3 b) (1/3)1/3 c) 1/ 3 d) 3 /1
25. Three closed vessel A,B and C are at the same temperature T and contain gases which obey the Maxwellian distribution of velocities. Vessel A contains only O2, B only N2 and C a mixture of equal quantities of O2 and N2. If the average speed of the O2 molecule in vessel A is V1 that of the N2 molecules in vessel B is V2, the average speed of the O2 molecules in vessel C is
a) (V1 + V2)/2 b) V1 c) (V1 V2)1/2 d) 3kT/M
26. When an ideal diatomic gas is heated at constant pressure, the fraction of the heat energy supplied which increases the internal energy of gas is
a) 2/5 b) 3/5 c) 3/7 d) 5/7 27. The equation of state of a gas is
V ) P aT (
+ 2 Vc = (RT +b)
where a,b,.c and R are constants. The isotherms can be represented by P = AVm – BVn, where A and B depend only on temperature. Hence
a) m = c and n = -1 b) m = -c and n = -1 c) m = c and n = 1 d) m = -c and n = 1
28. 22 gm of CO2 at 270C is mixed with 16 gm of O2 at 370C. The temperature of the mixture is a) 30.50C b) 34.50C c) 270C d) 320C
29. Heat is flowing through two cylindrical rods of the same material. The diameters of the rods are in the ratio 1:2 and the lengths in the ratio 2:1. If the temperature difference between the ends is the same, then the ratio of the rate of flow of heat through them will be
a) 1:1 b) 2:1 c) 1:4 d) 1:8
30. 2 g of hydrogen is mixed with 4 g of He. The ratio of specific heat of this mixture is a) 23/15 b) 3/2 c) 7/5 d) 5/3
31. A material has a specific heat given by the equation C = 0.5 T J/g0 C. What is heat required to raise the temperature of 2 g of this substance from 100 C to 200 C?
a) 10 J b) 20 J c) 50 J d) 150 J
32. The rms speed of oxygen molecules at T K is v. If temperature is doubled and oxygen dissociates, the rms speed would be
a) v b) 2v c) 2v d)v/ 2
33. If earth had no atmosphere, it would have been
a) slightly cooler b) very hot c) slightly hotter d) very cool 34. It is desirable to have for cooking vessels
a) low specific heat and low thermal conductivity b) low specific heat and high thermal conductivity c) high specific heat and low thermal conductivity d) high specific heat and high thermal conductivity
35. The external work done when 1 g of hydrogen is heated through 10C at constant pressure sis (in cal)
a) 1 b) 2 c) 4 d) 8
36. Two identical gas tanks are placed on the two pans of a beam balance. One tank is empty and open to the atmosphere. The second tank is evacuated and then filled with helium until the two tanks balance. The pressure of helium must be (in atmosphere)
a) 1 b) 4 c) 7.5 d) 15
37. A closed vessel contains 4 g of oxygen and 3.5 g of nitrogen. The total pressure is 8 atm. at the given temperature. If all the oxygen is removed from the system without allowing any change in temperature, then the pressure will become (in atmosphere)
a) 56/15 b) 64/15 c) 4 d) 70/8 38. Which of the following is the best conductor of heat ?
a) Copper b) Brass c) Aluminum d) Silver
39. If 1 mol of argon is mixed with 1 mol of oxygen. The external work done when this mixture is heated through 10C at constant pressure is
a) 3R b) 2R c) R d) 4R
40. The equation to a certain gas can be written as TV2/5 = constant. The heat required to raise the internal energy of 1 mol of this gas through 10C is
a) 2R b) 3R c) R d) 2.5R
41. A metallic ball and a highly stretched spring are made of the same material and have the same mass. They are heated so that they melt. The latent heat required
a) will be the same for both b) will be greater for the ball c) will be greater for the spring d) cannot be answered from the data 42. If λ denotes thermal conductivity, d density, c specific heat, then the units of λ/dc will be
a) m2s-1 b) m c) ms-2 d) s
43. The time period of a pendulum is x and its linear expansivity is α. When its temperature is raised by ∆T, the change in the time period is
a) 2α x ∆T b) 2α ∆T c) 2
1 α x ∆T d) 2 1 α ∆T
44. During an experiment an ideal gas is found to obey an additional law – VP2 = constant. the gas is initially at a temperature T and has volume V.When it expands to a volume 2V, the temperature becomes
a) 2√2 T b) 2
1T c) √3 T d) √2 T
45. One of the most efficient engines ever developed operates between 2100 K and 700 K. Its actual efficiency is 40%. The percentage fraction of its actual efficiency to its maximum efficiency is’
a) 48% b) 60% c) 72% d) 55%
46. When a gas is isothermally expanded so that its volume becomes twice, the rms velocity a) becomes twice b) becomes √2 times
c) remains the same d) becomes 0.7 times
47. If internal energy of a gas decreases by an amount equal to the external work, the gas is undergoing
a) adiabatic expansion b) adiabatic compression c) isothermal expansion d) isochoric expansion
48. In a certain process 100 calorie of heat is added to a system and it does 20 J of work on the surroundings. The internal energy of the system is
a) increased by 400 J b) increased by 120 J c) increased by 120 cal d) decreased by 400 J
49. If the temperature of a hot body is increased by 50%, the amount of radiation emitted by it would increase by nearly
a) 50% b) 225% c) 400% d) 500%
50. Two spheres of the same material have radii 1m and 4m and temperatures 4000 K and 2000 K respectively. The ratio of energy radiated per second by the first sphere to that of the second is
a) 16:1 b) 1:1 c) 4:1 d) 1:9
51. Two identical rods A and B when joined in series as in (fig1) conduct heat at a rate 4 W at thermal equilibrium. When they are joined in parallel as shown
(fig.2) under same temperature difference, they will conduct heat at a rate,
a) 1 W b) 2 W c) 4 W d) 16 W
52. Two stars radiate maximum energy at frequencies f1 = 2 x 1015 Hz and f2 = 2.5 x 1015 Hz respectively. The ratio of the temperature of the first to that of the second is
a) 4:5 b) 5:4 c) 25:16 d) 2:5
53. The ratio of energy emitted by two stars is 1:16. What is the ratio of the wavelengths carrying maximum energy of first to second
a) 1:2 b) 2:1 c) 4:1 d) 1:4
54. It takes 10 hours to form 1 cm thick layer of ice in a pond where the surrounding at temperature is –100C. The time to increase the thickness of ice from 1 cm to 2 cm is
a) 10 h b) 20 h c) 30 h d) 40 h 55. A system is in thermodynamic equilibrium if
a) no external force acts on it b) no chemical reaction takes place
c) no heat exchange takes place with the surroundings d) all the above three
56. The volume of an ideal gas increases to twice during an adiabatic change. In the process a) its internal energy increases b) its internal energy decreases
c) it entropy remains constant d) both (b) and (c)
57. A storage battery is charged with 20 A current at 12 V. The rate of transfer of heat from the battery is 10W. The rate of change of internal energy is
a) 240 J/s b) 230 J/s c) 460 J/s d) 46 J/s 58. Current in a filament lamp is doubled. The temperature of the lamp increases to
a) 2 times b) 4 times c) √2 times d) 2√2 times
A B
A
B
59. Three liquids of equal masses are thoroughly mixed. The specific heat capacities of liquids are C1, C2 and C3 and their temperatures are t1, t2 and t3 respectively. The temperature of the mixture is
a) (C1 + C2 + C3) / (t1 +t2 +t3)
b) (C1t1 + C2t2 + C3t3 ) / (C1 + C2 + C3) c) (C1t1 + C2t2 + C3t3) / (t1 + t2 + t3) d) (C1t1 + C2t2 + C3t3) / (C1t2 + C2t3 + C3t1)
60. The temperature at which the average kinetic energy of a molecule of a gas will be same as that of an electron accelerated through 1 volt is nearest to
a) 800 K b) 6700 K c) 7700 K d) 9200 K
61. If l is the length, A the are of cross-section and λ, the thermal conductivity, then the thermal resistance of a block is given by
a) λ 1/A b) 1/λA c) λA/l d) A/λl
62. A wall has two layers A and B each made of a different material. Both the layers have the same length and thickness. The thermal conductivity of the material of A is twice that of B.
Under thermal equilibrium, the temperature difference across the wall is 360C, end of A being at 00C. The temperature of interface of A and B is
a) 60C b) 120C c) 180C d) 240C
63. A sphere, a cube and a thin circular plate all made of same material and having the same mass are initially heated to a temperature of 800C. Which of them cools fastest when left in air at room temperature?
a) sphere b) cube c) circular plate d) all the same rate 64. A body cools from 700 to 600C in 10 minutes. To cool from 600 to 500C, under the same
surroundings of temperature 300C, it will take (in min)
a) 10 b) 13.33 c) 14 d) 11 65. Ten litre of benzene weighs:
a) more in summer than in winter b) more in winter than in summer c) equal in winter and summer d) cannot be answered from the data 66. The kinetic theory of gases breaks down most at
a) low pressure and high temperature b) high pressure and low temperature c) low pressure and low temperature d) high pressure and high temperature 67. When temperature of a gas is raised while its volume remains constant, the pressure exerted
by a gas on the walls of the container increases because it molecules a) lose more kinetic energy to the wall
b) are in contact with the wall for a shorter time c) strike the wall more often with higher velocities d) collide with each other less frequently
68. The kinetic energy of 1 g of helium gas at STP is
a) 819 J b) 933 J c) 3398 J d) 850 J
69. One mole of a diatomic gas and 1 mole of a monatomic gas are each given 1.5 kilo calories of heat at constant volume. The ratio of temperature rise of diatomic to monatomic is
a) 7/5 b) 5/7 c) 5/3 d) 3/5
70. A crystal has a coefficient of linear expansion 13 x 10-7 in one direction and 231 x 10-7 in each direction at right angles to it. Then it cubical expansivity is
a) 462 x 10-7 b) 244 x 10-7 c) 475 x 10-7 d) 257 x 10-7
71. An ideal gas is allowed to expand freely against vacuum in a rigid insulated container. The gas undergoes
a) increase in internal energy b) increase in temperature
c) decrease in internal energy but increase in temperature d) neither an increase nor decrease in internal energy
72. Oxygen and helium of equal volume V at the same temperature T and same pressure P are mixed to have a volume V. The resulting pressure of the mixture will be
a) 2P b) P c) P/2 d) P/4
73. Two stars A and B of equal surface area radiate maximum energy at 3600 A0 And 4800 A0 respectively. Then the ratio of total power radiated by A to that of B will be
a) 256:81 b) 3:4 c) 4:3 d) 81:256 74. Check which of the following statements is not correct for an ideal gas
a) the change in internal energy in a constant pressure process from temperature T1 to T2 is equal to nCp (T2-T1), where Cp is the molar heat capacity at constant pressure and n the number of moles of the gas.
b) the change in internal energy of the gas and the work done by the gas are equal in magnitude in an adiabatic process
c) the internal energy does not change in an isothermal process d) no heat is added or removed in an adiabatic process 75. The adiabatic elasticity of helium at STP is
a) 1.4 x 105 Pa b) 1.53 x 105 Pa c) 1.66 x 105 Pa d) 1 x 105 Pa
76. A surface at a temperature T0 K receives heat from a source at a temperature T K (T >> T0), at a distance r from the source. If the temperature and distance are doubled, the power P1
received by the surface becomes approximately (P original power)
a) P b) 2P c) 4P d) 16 P 77. Two rods of same length and area but made of different materials are
welded together as shown in the fig. If λ1 and λ2 are the thermal conductivity of each of them respectively, the thermal conductivity of the system will be
a) λ1 + λ2 b) λ1 λ2 / λ1 + λ2 c) 2λ1 λ2 / λ1 +λ2 d) λ1 + λ2/2
78. A bullet is stopped by a target the temperature rise of the bullet is ∆T, without loss of energy.
If the bullet’s velocity is doubled and it loses 50% of the energy, the rise in temperature of the bullet will be
a) ∆T b) 2∆T c) 3 ∆T d) 4 ∆T
79. One mol of monatomic gas is heated from 00C to 1000C at constant pressure. The change in its internal energy is
a) 2.3 J b) 12.4 J c) 120 J d) 1250 J
80. If a temperature of source and sink of a Carnot engine is increased by 10% its efficiency a) increases by 10% b) decreases by 10%
c) increases by 1% d) remains the same
81. A test tube of water at 40C is immersed inside a large block of ice. Which of the following will happen?
a) Water in the test tube will freeze b) Water in the test tube will not cool
c) Water in the test tube will reach freezing point but will not freeze
1 2
d) water in the test tube will reach between freezing point and 40 C 82. Which of the following cases, the work done by a gas is minimum ?
a) 1 b) 2 c) 3 d) 4
83. If distance between sun and earth is reduced to half the present value, solar constant a) increases to 4 times b) increases to 2 times
c) decreases to 4 times d) remains the same
84. A cylinder of radius R made of a material of thermal conductivity K1 is surrounded by a cylindrical shell of inner radius R and outer radius 2R
made of a material of thermal conductivity K2. The two ends of the combined system are maintained at two different temperatures. there is no loss of heat across the cylindrical surface and the system is in a steady state. The effective thermal conductivity of the system is
a) K1 + K2 b) K1 K2 / (K1 +K2) c) K1 + 3K2)/4 d) (3K1 + K2)/4
85. A cube of side a is heated through 1oC. If α is the linear expansivity of the material of the cube, its increase in area is
a) a2α b) 4a2α c) 6a2α d) 12 a2α
86. The maximum temperature of 1g hot water which can be mixed with 1g ice at 0o C so that the temperature remains at 0o C, is
a) 10o C b) 200 C c) 50o C d) 80o C
87. 3.12 kJ of heat is supplied to a mass of monatomic gas produces a temperature rise. If the same amount of heat is supplied to a diatomic gas of same mass, the temperature rise will be a) same b) 7/5 times c) 3/5 times d) 5/7 times
88. 16 g of oxygen at STP is mixed with 14 g of nitrogen at 10o C . The resulting temperature of the mixture will be
a) 0oC b) 5oC
c) slightly more than 5oC d) slightly less than 5oC
89. A substance of mass M requires an input power P to remain in the molten state at its melting point. When the power source is turned off the sample completely solidifies in a time t. The latent heat of fusion of the substance is
a) Pt/M b) P/Mt c) Mt/T d) MP/t
90. 2 g of He is heated through 1oC at constant pressure. . The external work done in the process is
a) R/2 b) R c) 3R/2 d) 2R
91. The RMS speed of hydrogen molecules at a temperature T is x m/s. At a temperature 4T, hydrogen dissociates. At this temperature the RMS speed of hydrogen will be
a) 2x b) 4x c) (2√2) x d) 4√2 x
92. Two metals A and B are used to make a compensated pendulum. If the linear expansivity of A to that of B is in the ratio 3:1, the ratio of length of A to that of B will be
K1 K2 R
2 R
1 2
X Y
X Y
X Y
X Y
V P
(1 ) (2 ) (3 ) (4 )
a) 3:1 b) 1:3 c) 1.5:1 d) 1:1.5
93. 1 mol of hydrogen is mixed with 1 mol of helium at the same temperature. The ratio of specific heats γ of the mixture is
a) 1.67 b) 1.4 c) 1.5 d) 1.53
94. A thin steel wire of length `L’ increases in length by 1% when heated through a certain range of temperature. If a thin steel plate of area 2LxL is heated through same range of temperature, the percentage increase in area will be
a) 1% b) 2% c) 3% d) 4%
95. A gas of γ = 4/3 is heated at constant pressure what percentage of total heat supplied is used as external work ?
a) 25% b) 20% c) 10% d) 5%
96. An electric heater of constant power takes 50 seconds to turn x g of ice at 0o C into water at 100o C. The time it will take to turn this water into steam at 100o C is
a) 25 s b) 50 s c) 100 s d) 150 s
97. A mixture is formed with one mol of monatomic gas, 1 mol of diatomic gas and 1 mol of triatomic gas. The external work done when this mixture is heated through 1oC is
a) R b) 6R c) 1.5R d) 3R
98. The ratio of diameter of molecule A to that of B is 1:2. The mean free path of A to B when they have same concentration, will be in the ratio
a) 1:2 b) 1:4 c) 2:1 d) 4:1
99. 22.2 g of ice at 0o C is mixed with 22.2g of water at 22.2o C. The resulting temperature of the mixture is
a) 22.2o C b) 11.1o C c) 0o C d) 5.6o C
100. An ideal monatomic gas is heated at constant pressure . What fraction of heat energy
100. An ideal monatomic gas is heated at constant pressure . What fraction of heat energy