Thermal Properties & Calorimetry PYQs Set 3 (PDF)

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Mere Teacher · Previous Year Questions NEET Physics · Thermal Properties & Calorimetry · Set 3 (Q61-90)
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61. $Two liquids A and B have θ_{A} and θ_{B} as contact angles in a capillary tube. If K = cos θ_{A} / cos θ_{B}, then identify the correct statement:$ (1) $K is negative, then liquid A and liquid B have convex meniscus.$ (2) $K is negative, then liquid A and liquid B have concave meniscus.$ (3) $K is zero, then liquid A has convex meniscus and liquid B has concave meniscus.$ (4) $K is negative, then liquid A has concave meniscus and liquid B has convex$ 62. $Two spherical bodies of same materials having radii 0.2 m and 0.8 m are placed in same atmosphere. The temperature of the smaller body is 800 K and temperature of the bigger body is 400 K. If the energy radiated from the smaller body is E, the energy radiated from the bigger body is (assume, effect of the surrounding temperature to be negligible),$ (1) $16 E$ (2) $E$ (3) $64 E$ (4) $256 E$ 63. $Two uniform brass rods A and B of length ' P' and ' 2 ? and their radii ' 2 r' and ' r' respectively are heated to same temperature. The ratio of the increase in the volume of rod A to that of rod B is$ (1) $1 : 1$ (2) $1 : 2$ (3) $2 : 1$ (4) $1 : 4$ 64. $The quantities of heat required to raise the temperatures of two copper spheres of radii r_{1} and r_{2} (r_{1} = 1.5 r_{2}) through 1 K are in the ratio of$ (1) $27/8$ (2) $9/4$ (3) $3/2$ (4) $1$ 65. $Hot water cools from 60^{\circ} C to 50^{\circ} C in the first 10 minutes and to 42^{\circ} C in the next 10 minutes. Then the temperature of the surroundings is$ (1) $20^{\circ} C$ (2) $30^{\circ} C$ (3) $15^{\circ} C$ (4) $10^{\circ} C$ 66. $A hot body is allowed to cool. The surrounding temperature is constant at 30^{\circ} C . The body takes time t_{1} to cool from 90^{\circ} C to 89^{\circ} C and time t_{2} to cool from 60^{\circ} C to 59.5^{\circ} C . Then,$ (1) $t_{2} = 2 t_{1}$ (2) $t_{2} = t_{1} / t_{2}$ (3) $t_{2} = 4 t_{1}$ (4) $t_{2} = t_{1}$ 67. $If the cold junction of a thermo-couple is kept at 0^{\circ} C and the hot junction is kept at T^{\circ} C, then the relation between neutral temperature (T_{n}) and temperature of inversion (T_{i}) is$ (1) $T_{n} = 2 T_{i}$ (2) $T_{n} = T_{i} - T$ (3) $T_{n} = T_{i} + T$ (4) $T_{n} = T_{i} /2$ 68. $Two water drops each of radius ' r' coalesce to form a bigger drop. If ' T' is the surface tension, the surface energy released in this process is:$ (1) $4 π r^{2} T (2 - 2^{1/3})$ (2) $4 π r^{2} T [1 + 2]$ (3) $4 π r^{2} T (2 - 2^{2/3})$ (4) $4 π r^{2} T [2 - 1]$ 69. $n moles of an ideal gas with constant volume heat capacity C_{V} undergo an isobaric expansion by certain volume. The ratio of the work done in the process, to the heat supplied is:$ (1) $\frac{nR}{C _{V} + nR}$ (2) $\frac{nR}{C _{V} - nR}$ (3) $\frac{4 nR}{C _{V} - nR}$ (4) $\frac{4 nR}{C _{V} + nR}$ 70. $A sphere, a cube and a thin circular plate all made of same material and having the same mass are heated to same temperature of 200^{\circ} C . When these are left in a room$ (1) $the sphere reaches room temperature fast.$ (2) $the cube reaches room temperature fast.$ (3) $the circular plate reaches room temperature fast.$ (4) $all will reach the room temperature simultaneously.$ 71. $0.1 m^{3} of water at 80^{\circ} C is mixed with 0.3 m^{3} of water at 60^{\circ} C . The final temperature of the mixture is$ (1) $65^{\circ} C$ (2) $70^{\circ} C$ (3) $60^{\circ} C$ (4) $75^{\circ} C$ 72. $An electric bulb is rated as 200 W. What will be the peak magnetic field at 4 m distance produced by the radiations coming from this bulb? Consider this bulb as a point source with 3.5% efficiency.$ (1) $1.19 x 1 0^{- 8} T$ (2) $1.71 x 1 0^{- 8} T$ (3) $0.84 x 1 0^{- 8} T$ (4) $3.36 x 1 0^{- 8} T$ 73. $A body cools in 7 minutes from 60°C to 40°C. The temperature of the surrounding is 10°C. The temperature of the body after the next 7 minutes will be$ (1) $30°C$ (2) $32 C$ (3) $34°C$ (4) $28°C$ 74. $Two stars A and B radiate maximum energy at the wavelengths of 360 nm and 480 nm respectively. Then the ratio of the surface temperatures of A and B is$ (1) $3 : 4$ (2) $81 : 256$ (3) $4 : 3$ (4) $256 : 81$ 75. $One mole of an ideal gas passes through a process where pressure and volume obey the relation P = P_{0} (1 - \frac{1}{2} (\frac{V _{0}}{V})^{2}) Here P_{o} and V_{o} are constants. Calculate the charge in the temperature of the gas if its volume changes from V_{o} to 2 V_{o}$ (1) $\frac{1}{2} \frac{P _{o} V _{o}}{R}$ (2) $\frac{5}{4} \frac{P _{o} V _{o}}{R}$ (3) $\frac{3}{4} \frac{P _{o} V _{o}}{R}$ (4) $\frac{1}{4} \frac{P _{o} V _{o}}{R}$ 76. $The resistances of the platinum wire of a platinum resistance thermometer at the ice point and steam point are 8Ω and 10Ω respectively. After inserting in a hot bath of temperature 400^{\circ} C, the resistance of platinum wire is$ (1) $10Ω$ (2) $8Ω$ (3) $16Ω$ (4) $2Ω$ 77. $One kg of water, at 20° C, is heated in an electric kettle whose heating element has a mean (temperature averaged) resistance of 20 Ω. The rms voltage in the mains is 200 V. Ignoring heat loss from the kettle, time taken for water to evaporate fully, is close to: [Specific heat of water = 4200 J/(kg °C), Latent heat of water = 2260 kJ / kg]$ (1) $16 minutes$ (2) $22 minutes$ (3) $3 minutes$ (4) $30 minutes$ 78. $A gas based geyser heats water flowing at the rate of 5.0 litres per minute from 27^{\circ} C to 87^{\circ} C . The rate of consumption of the gas is____g / s . (Take heat of combustion of gas = 5.0 \times 10^{4} J / g) specific heat capacity of water = 4200 J / kg \cdot^{\circ} C$ (1) $0.42$ (2) $2.1$ (3) $0.21$ (4) $4.2$ 79. $When M_{1} gram of ice at - 10° C (Specific heat 0.5 cal g^{- 1} ° C^{- 1}) is added to M_{2} gram of water at 50° C, finally no ice is left and the water is at 0° C. The value of latent heat of ice, in cal g^{- 1} is:$ (1) $\frac{50 M _{2}}{M _{1}} - 5$ (2) $\frac{5 M _{1}}{M _{2}} - 50$ (3) $\frac{50 M _{2}}{M _{1}}$ (4) $\frac{5 M _{2}}{M _{1}} - 5$ 80. $The two ends of a metal rod are maintained at temperatures 100^{\circ} C and 110^{\circ} C . The rate of heat flow in the rod is found to be 4.0 J / s . If the ends are maintained at temperatures 200^{\circ} C and 210^{\circ} C, the rate of heat flow will be$ (1) $44.0 J / s$ (2) $16.8 J / s$ (3) $8.0 J / s$ (4) $4.0 J / s$ 81. $A thermally insulted vessel contains 150g of water at 0°C. Then the air from the vessel is pumped out adiabatically. A fraction of water turns into ice and the rest evaporates at 0° C itself. The mass of evaporated water will be closed to:(Latent heat of vaporization of water & Latent heat of Fusion of water )$ (1) $150 g$ (2) $20 g$ (3) $130 g$ (4) $35 g$ 82. $Half mole of an ideal monoatomic gas is heated at constant pressure of 1 atm from 20^{\circ} C to 90^{\circ} C . Work done by gas is close to: (Gas constant R = 8.31 J / mol - K)$ (1) $581 J$ (2) $291 J$ (3) $146 J$ (4) $73 J$ 83. $A Carnot engine has an efficiency of 1/6 When the temperature of the sink is reduced by 62^{\circ} C, its efficiency is doubled. The temperatures of the source and the sink are, respectively.$ (1) $62^{\circ} C, 124^{\circ} C$ (2) $99^{\circ} C, 37^{\circ} C$ (3) $124^{\circ} C, 62^{\circ} C$ (4) $37^{\circ} C, 99^{\circ} C$ 84. $100 g of ice at 0^{\circ} C is mixed with 100 g of water at 100^{\circ} C . The final temperature of the mixture is [Take L_{f} = 3.36 \times 10^{5} J kg^{- 1} and S_{w} = 4.2 \times 10^{3} J kg^{- 1} K^{- 1}]$ (1) $40^{\circ} C$ (2) $10^{\circ} C$ (3) $50^{\circ} C$ (4) $1^{\circ} C$ 85. $The specific heat capacity of a metal at low temperature (T) is given as C_{p} (k j K^{-1} k g^{-1}) = 32 (\frac{T}{400})^{3} A 100 gram vessel of this metal is to be cooled from 20K to 4K by a special refrigerator operating at room temperature (27ºC). The amount of work required to cool the vessel is:$ (1) $greater than 0.148 kJ$ (2) $between 0.148 kJ and 0.028 kJ$ (3) $less than 0.028 kJ$ (4) $equal to 0.002 kJ$ 86. $A copper ball of mass 100 gm is at a temperature T. It is dropped in a copper calorimeter of mass 100 gm, filled with 170 gm of water at room temperature. Subsequently, the temperature of the system is found to be 75º C. T is given by: (Given: room temperature = 30ºC, specific heat of copper = 0.1 cal/gmºC)$ (1) $825º C$ (2) $800ºC$ (3) $885ºC$ (4) $1250ºC$ 87. $The side of a copper cube is 1 m at 0^{\circ} C . What will be the change in its volume, when it is heated to 100^{\circ} C ? (α_{copper} = 18 \times \frac{10 ^{- 6}}{^{\circ} C})$ (1) $45 \times 10^{- 4} m^{3}$ (2) $54 \times 10^{- 4} m^{3}$ (3) $34 \times 10^{- 4} m^{3}$ (4) $64 \times 10^{- 4} m^{3}$ 88. $Three identical rods A, B and C are placed end to end. A temperature difference is maintained between the free ends of A and C . The thermal conductivity of B is thrice that of C and half of that of A . The effective thermal conductivity of the system will be (K_{A} is the thermal conductivity of rod A)$ (1) $\frac{1}{3} K_{A}$ (2) $3 K_{A}$ (3) $2 K_{A}$ (4) $\frac{2}{3} K_{A}$ 89. $Following figure shows two processes A and B for a gas. If Δ Q_{A} and Δ Q_{B} are the amount of heat absorbed by the system in two cases, and Δ U_{A} and Δ U_{B} are changes in internal energies, respectively, then:$ (1) $Δ Q_{A} < Δ Q_{B}, Δ U_{A} < Δ U_{B}$ (2) $Δ Q_{A} > Δ Q_{B}, Δ U_{A} > Δ U_{B}$ (3) $Δ Q_{A} > Δ Q_{B}, Δ U_{A} = Δ U_{B}$ (4) $Δ Q_{A} = Δ Q_{B}; Δ U_{A} = Δ U_{B}$ 90. $Two identical rods AC and CB made of two different metals having thermal conductivities in the ratio 2 : 3 are kept in contact with each other at the end C as shown in the figure. A is at 100^{\circ} C and B is at 25^{\circ} C . Then the junction C is at$ (1) $55^{\circ} C$ (2) $60^{\circ} C$ (3) $75^{\circ} C$ (4) $50^{\circ} C .$