Thermodynamics PYQs Set 11 (PDF)

Set 11 of 16 · Questions 301-330 of 459

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Mere Teacher · Previous Year Questions NEET Physics · Thermodynamics · Set 11 (Q301-330)
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301. $A Carnot engine working between 300 K and 600 K has a work output of 800 J per cycle. The amount of heat energy supplied to the engine from the source per cycle is -$ (1) $1200 J$ (2) $2400 J$ (3) $1600 J$ (4) $3200 J$ 302. $A balloon filled with helium (32^{\circ} C and 1.7 atm.) bursts. Immediately afterwards the expansion of helium can be considered as$ (1) $Irreversible adiabatic$ (2) $Reversible adiabatic$ (3) $Irreversible isothermal$ (4) $Reversible isothermal$ 303. $For a diatomic gas, if γ_{1} = (\frac{Cp}{Cv}) for rigid molecules and γ_{2} = (\frac{Cp}{Cv}) for another diatomic molecules, but also having vibrational modes. Then, which one of the following options is correct? (Cp and Cv are specific heats of the gas at constant pressure and volume)$ (1) $γ_{2} = γ_{1}$ (2) $2 γ_{2} = γ_{1}$ (3) $γ_{2} < γ_{1}$ (4) $γ_{2} > γ_{1}$ 304. $A Carnot engine take 5000 kcal of heat from a reservoir at 727°C and gives heat to a sink at 127°C. The work done by the engine is:$ (1) $3 x 1 0^{6} J$ (2) $Zero$ (3) $12. 6 x 1 0^{6} J$ (4) $8. 4 x 1 0^{6} J$ 305. $Two heat engines A and B have their sources at 1000 K and 1100 K and their sinks are at 500 K and 400 K respectively. What is true about their efficiencies?$ (1) $ηA = ηB$ (2) $ηA>ηB$ (3) $ηA<ηB$ (4) $Cannot predict.$ 306. $In a Carnot's engine if the temperatures of the source and the sink are decreased by 100 K each then the efficiency of the engine$ (1) $increases$ (2) $decreases$ (3) $remains constant$ (4) $becomes one$ 307. $The specific heat of helium at constant volume is 12.6 J mol^{- 1} K^{- 1} . The specific heat of helium at constant pressure in J mol^{- 1} K^{- 1} is approximately (assume, the universal gas constant, R = 8.314 J mol^{- 1} K^{- 1})$ (1) $12.6$ (2) $16.8$ (3) $18.9$ (4) $20.9$ 308. $A hammer of mass 200 kg strikes a steel block of mass 200 g with a velocity 8 ms^{- 1} . If 23 % of the energy is utilized to heat the steel block, the rise in temperature of the block is (specific heat capacity of steel = 460 J kg^{- 1} K^{- 1})$ (1) $8 K$ (2) $16 K$ (3) $12 K$ (4) $24 K$ 309. $The phenomena of lowering freezing point of water by the application of pressure is known as$ (1) $Sublimation$ (2) $Regelation$ (3) $Precipitation$ (4) $Crystallization$ 310. $Three very large plates of same area are kept parallel and close to each other. They are considered as ideal black surfaces and have very high thermal conductivity. First and third plates are maintained at absolute temperatures 2 T and 3 T respectively. Temperature of the middle plate in steady state is$ (1) $(\frac{65}{2})^{\frac{1}{4}} T$ (2) $(\frac{97}{4})^{\frac{1}{4}} T$ (3) $(\frac{97}{2})^{\frac{1}{4}} T$ (4) $(97)^{\frac{1}{4}} T$ 311. $When the door of a refrigerator is kept open then the room temperature starts$ (1) $Cool down$ (2) $Hot up$ (3) $First cool down then hot up$ (4) $Neither cool down nor hot up$ 312. $A Carnot engine operating between temperatures 600 K and 300 K, absorbs 800 J of heat from the source. The mechanical work done per cycle is$ (1) $400 J$ (2) $650 J$ (3) $750 J$ (4) $600 J$ 313. $An electric appliance supplies 6000J/min heat to the system. If the system delivers a power of 90W. How long it would take to increase the internal energy by 2. 5 x 1 0^{3} J?$ (1) $2. 5 x 1 0^{2} s$ (2) $4.1 x 1 0^{1} s$ (3) $2.4 x 1 0^{3} s$ (4) $2. 5 x 1 0^{1} s$ 314. $A monoatomic gas does 100 J of work when it is expanded isobarically. How much of heat is given to the gas in the process.$ (1) $150 J$ (2) $200 J$ (3) $250 J$ (4) $300 J$ 315. $A diatomic gas has an initial internal energy of 80 cal. A work of 18 cal is done on the gas and the gas releases heat energy of 42 J . The final internal energy of the gas is$ (1) $20 J$ (2) $369.6 J$ (3) $54 J$ (4) $20 cal$ 316. $To raise the temperature of a certain mass of gas by 50^{\circ} C at a constant pressure, 160 calories of heat is required. When the same mass of gas is cooled by 100^{\circ} C at constant volume, 240 calories of heat is released. How many degrees of freedom does each molecule of this gas have (assume gas to be ideal)?$ (1) $6$ (2) $7$ (3) $3$ (4) $5$ 317. $An ideal gas, undergoing adiabatic change, has which of the following pressure temperature relationship?$ (1) $P^{γ} T^{1 - γ} = constant$ (2) $P^{1 - γ} T^{γ} = constant$ (3) $P^{γ - 1} T^{γ} = constant$ (4) $P^{γ} I^{γ - 1} = constant.$ 318. $A heat engine has an efficiency η . Temperatures of source and sink are each decreased by 100 K. The efficiency of the engine$ (1) $Increases$ (2) $Decreases$ (3) $Remains constant$ (4) $Becomes 1$ 319. $The temperature of sink of Carnot engine is 2 7^{0} C and its efficiency is 25%. The temperature of source is$ (1) $22 7^{0} C$ (2) $12 7^{0} C$ (3) $2 7^{0} C$ (4) $32 7^{0} C$ 320. $Consider a Carnot cycle operating between source temperature 750 K and sink temperature 350 K producing 1.25 kJ of mechanical work per cycle, the heat transferred to the engine by the reservoirs$ (1) $1.34 kJ$ (2) $2.34 kJ$ (3) $3.34 kJ$ (4) $4.34 kJ$ 321. $The Carnot heat engine have an efficiency of 50 % . The temperature of sink is maintained at 500 K . To increase the efficiency upto 80 %, the increment in the source temperature is$ (1) $1500 K$ (2) $2500 K$ (3) $500 K$ (4) $2000 K$ 322. $At 1 0^{o} C the value ofthe density of a fixed mass of an ideal gas divided by its pressure is x . At 11 0^{o} C this ratio is$ (1) $\frac{10}{110} x$ (2) $\frac{283}{383} x$ (3) $x$ (4) $\frac{383}{283} x$ 323. $The (WlQ) of a Carnot engine is 1/6, now the temperature ofsink is reduced by 6 2^{o} C, then this ratio becomes twice, therefore the initial temperature ofthe sink and source are respectively$ (1) $3 3^{o} C, 6 7^{o} C$ (2) $3 7^{o} C, 9 9^{o} C$ (3) $6 7^{o} C, 3 3^{o} C$ (4) $97 K, 37 K.$ 324. $One mole of an ideal monatomic gas undergoes a process described by the equation P V^{3} = constant. The heat capacity ofthe gas during this process is$ (1) $3 2 R$ (2) $5 2 R$ (3) $2 R$ (4) $R$ 325. $Density of water at 4^{\circ} C and 20^{\circ} C are 1000 kg / m^{3} and 998 kg / m^{3} respectively. The increase in internal energy of 4 kg of water when it is heated from 4^{\circ} C to 20^{\circ} C is____J. (specific heat capacity of water = 4.2 J / kg . and 1 atmospheric pressure = 10^{5} Pa)$ (1) $234699.2$ (2) $315826.2$ (3) $258700.8$ (4) $268799.2$ 326. $The temperature of reservoir of Carnot's engine operating with an efficiency of 70% is 1000K. The temperature of its sink is$ (1) $300 K$ (2) $400 K$ (3) $500 K$ (4) $700 K$ 327. $10 mole of an ideal gas is undergoing the process shown in the figure. The heat involved in the process from P_{1} to P_{2} is α Joule (P_{1} = 21.7 Pa and P_{2} = 30 Pa, C_{v} = 21 J / K . mol, R = 8.3 J / mol . K). The value of α is____.$ (1) $21$ (2) $15$ (3) $28$ (4) $24$ 328. $Figure below shows two paths that may be taken by a gas to go from a state A to a state C . In process AB, 400 J of heat is added to the system and in process BC, 100 J ofheat is added to the system. The heat absorbed by the system in the process AC will be$ (1) $460 J$ (2) $300 J$ (3) $380 J$ (4) $500 J$ 329. $The p - V diagram shown below indicates two paths along which a sample of gas can be taken from state A to state B . The energy equal to 5 pV in the form of heat is required to be transferred, if the Path-I is chosen. How much energy in the form of heat should be transferred, if Path-2 is chosen?$ (1) $\frac{11}{2} pV$ (2) $6 pV$ (3) $\frac{9}{2} pV$ (4) $7 pV$ 330. $A Carnot engine with efficiency 50% takes heat from a source at 600 K. In order to increase the efficiency to 70%, keeping the temperature of sink same, the new temperature of the source will be:$ (1) $360K$ (2) $1000 K$ (3) $900K$ (4) $300K$