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NCERT Solutions for class 11 Physics | Chapter 12 - Thermodynamics

(1) A gas expands from 1 litre to 3 litre at atmospheric pressure. The work done by the gas is about
[A] 200 J
[B] 2 J
[C] 300 J
[D] 400 j
Answer: 200 J
(2) A uniform metal rod is used as a bas pendulum. If the room temperature rises by 10C and the efficient of line as expansion of the metal of the rod is, 2×10-6 0-1 Cwhat will have percentage increase in the period of the pendulum ?
[A] -2×10-3
[B] 1×10-3
[C] -1×10-3
[D] 2×10-3
Answer: 1×10-3

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(3) A Centigrade and a Fahrenheit thermometers are dipped in boiling water-The water temperature is lowered until the Fahrenheit thermometers registered 140 what is the fall in thermometers
[A] 80
[B] 60
[C] 40
[D] 30
Answer: 40
(4) The temperature of a body on Kelvin Scale is found to be x.K. when it is measured by Fahrenheit thermometers. it is found to be xF, then the value of x is .
[A] 313
[B] 301.24
[C] 574-25
[D] 40
Answer: 574-25
(5) The temperature on Celsius scale is 25 C What is the corresponding temperature on the Fahrenheit Scale?
[A] 40 F
[B] 45 F
[C] 50 F
[D] 77 F
Answer: 77 F
(6) At Which temperature the density of water is maximum?
[A] 4 F
[B] 42 F
[C] 32 F
[D] 39.2 F
Answer: 39.2 F
(7) The temperature of a substance increases by 27°C What is the value of this increase of Kelvin scale?
[A] 30K
[B] 2-46K
[C] 7 K
[D] 27 K
Answer: 27 K
(8) A gas mixture consists of 2 mde of oxygen and 4 mole of argon at tempressure T.Neglecting all vibrational modes, the total internal energy of the system is
[A] 11 RT
[B] 9 RT
[C] 15 RT
[D] 4 RT
Answer: 11 RT
(9) One mole of a monoatomic gas is heate at a constant pressure of 1 atmosphere from 0k to 100 k. If the gas constant R = 8.32 J/mol k the change in internal energy of the gas is approximate ?
[A] 23 J
[B] 1.25×103 J
[C] 8.67× 103 J
[D] 46 J
Answer: 46 J
(10) One mole of a monoatomic ideal gas is mixed with one mole of a diatomic ideal gas The molas specific heat of the micture at constant volume is ____
[A] 4 R
[B] 3 R
[C] R
[D] 2R
Answer: 2R
(11) If du represents the increase in internal energy of a thesmodynamic system and dw the work done by the system, which of the following statement is true ?
[A] du = dw in isothermal process
[B] du = dw in aidabadic process
[C] du = - dw in an aidabadic process
[D] da = - dw in an isothermal process
Answer: du = - dw in an aidabadic process
(12) An engine is supposed to operate between two reservoirs at temperature 727°C and 227°C. The maximum possible efficiency of such an engine is
[A] 3/4
[B] 1/4
[C] 1/2
[D] 1
Answer: 1/2
(13) An ideal refrigerator has a freetes at a temperature of -13°C, The coefficent of perfomance of the engine is 5. The temperature of the air to which heat is rejected will be.
[A] 325°C
[B] 39°C
[C] 325 K
[D] 320°C
Answer: 39°C
(14) An ideal heat engine working between temperature T1 and T2 has an efficiency n. The new efficiency if both the source and sink temperature are doubled, will be
[A] n
[B] 2n
[C] 3n
[D] n/2
Answer: n
(15) For which combination of working temperatures the efficiency of Car not's engine is highest.
[A] 80 K, 60 K
[B] 100 K, 80 K
[C] 60 K, 40 K
[D] 40 K, 20 K
Answer: 40 K, 20 K
(16) A car not engine takes 3×106 cal of heat from a reservoir at 627°C , and gives to a sink at 27°C. The work done by the engine is
[A] 4.2×106 J
[B] 16.8×106 J
[C] 8.4×106 J
[D] Zero
Answer: 8.4×106 J
(17) Efficiency of a car not engine is 50%, when temperature of outlet is 500K. in order to increase efficiency up to 60% keeping temperature of intake the same what is temperature of out let.
[A] 200 K
[B] 400 K
[C] 600 K
[D] 800 K
Answer: 400 K
(18) If the doors of a refrigerators is kept open, then which of the following is true?
[A] Room is cooled
[B] Room is eithers cooled or heated
[C] Room is neither cooled nor heated
[D] Room is heated
Answer: Room is heated
(19) If a heat engine absorbs 2KJ heat from a heat source and release 1.5KJ heat into cold reservoir, then its efficiency is ____
[A] 0.5%
[B] 75%
[C] 25%
[D] 50%
Answer: 25%
(20) The efficiency of heat engine is 30% If it gives 30KJ heat to the heat sink, than it should have absorbed _____ KJ heat from heat source.
[A] 42.8
[B] 39
[C] 29
[D] 9
Answer: 42.8

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