NEET Physics Thermodynamics MCQs Set A

Question. If an average person jogs, he produces 14.5 × 10³ cal/min. This is removed by the evaporation of sweat. The amount of sweat evaporated per minute (assuming 1 kg requires 580 × 10³ cal for evaporation) is
(a) 0.025 kg
(b) 2.25 kg
(c) 0.05 kg
(d) 0.20 kg

Answer: A

Question. Assertion : Adiabatic expansion is always accompanied by fall in temperature.
Reason : In adiabatic process, volume is inversely proportional to temperature.
(a) Assertion is correct, reason is incorrect
(b) Assertion is incorrect, reason is correct.
(c) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(d) Assertion is correct, reason is correct; reason is a correct explanation for assertion

Answer: A

Question. One mole of O₂ gas having a volume equal to 22.4 Litres at 0°C and 1 atmospheric pressure in compressed isothermally so that its volume reduces to 11.2 litres. The work done in this process is-
(a) –1572.5 J
(b) 1728 J
(c) 1672.5 J
(d) –1728 J

Answer: A

Question.  An ideal gas is compressed to half its initial volume by means of several processes. Which of the process results in the maximum work done on the gas?
(a) Adiabatic
(b) Isochoric
(c) Isobaric
(d) Isothermal

Answer: A

Question.  The coefficient of performance of a refrigerator is 5. If the inside temperature of freezer is -20°C, then the temperature of the surroundings to which it rejects heat is
(a) 31°C
(b) 21°C
(c) 11°C
(d) 41°C

Answer: A

Question.  A gas is compressed isothermally to half its initial volume. The same gas is compressed separately through an adiabatic process until its volume is again reduced to half. Then
(a) Compressing the gas through adiabatic process will require more work to be done
(b) Compressing the gas isothermally will require more work to be done
(c) Compressing the gas isothermally or adiabatically will require the same amount of work.
(d) Which of the case (whether compression through isothermal or through adiabatic process) requires more work will depend upon the atomicity of the gas

Answer: A

Question.  A refrigerator works between 4°C and 30°C. It is required to remove 600 calories of heat every second in order to keep the temperature of the refrigerated space constant. The power required is: (Take 1 cal = 4.2 joules)
(a) 236.5 W
(b) 2365 W
(c) 23.65
(d) 2.365 W

Answer: A

Question. The internal energy change in a system that has absorbed 2 kcals of heat and done 500 J of work is
(a) 7900 J
(b) 8900 J
(c) 5400 J
(d) 6400 J

Answer: A

Question.  In a heat engine, the temperature of the source and sink are 500 K and 375 K. If the engine consumes 25 × 10⁵ J per cycle, the work done per cycle is
(a) 6.25 × 10⁵ J
(b) 2.19 × 10⁵J
(c) 3 × 10⁵ J
(d) 4 × 10⁴ J

Answer: A

Question. Assertion : The heat supplied to a system is always equal to the increase in its internal energy.
Reason : When a system changes from one thermal equilibrium to another, some heat is absorbed by it.
(a) Assertion is incorrect, reason is correct.
(b) Assertion is correct, reason is incorrect
(c) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(d) Assertion is correct, reason is correct; reason is a correct explanation for assertion

Answer: A

Question.  A sample of 0.1 g of water at 100°C and normal pressure (1.013 × 10⁵ Nm^–2) requires 54 cal of heat energy to convert to steam at 100°C. If the volume of the steam produced is 167.1 cc, the change in internal energy of the sample, is
(a) 208.7 J
(b) 104.3 J
(c) 84.5 J
(d) 42.2 J

Answer: A

Question.  The efficiency of an ideal heat engine working between the freezing point and boiling point of water, is
(a) 26.8%
(b) 20%
(c) 12.5%
(d) 6.25%

Answer: A

Question.  A diatomic gas which has initial volume of 10 liter is isothermally compressed to 1/15th of its original volume where initial pressure is 10⁵ Pascal. If temperature is 27°C them find the work done by gas.
(a) –2.70 × 10³ J
(b) –1.35 × 10³ J
(c) 2.70 × 10³ J
(d) 1.35 × 10³ J

Answer: A

Question.  If 1 cm³ of water is vaporized (latent heat of vaporization = 5.40 cal/g°C) at P = 1 atm. If the volume of steam formed is 1671 cm³ calculate increase internal energy.
(a) 373 cal
(b) 473 cal
(c) 573 cal
(d) 673 cal

Answer: A

Question. Assertion: Energy of an isolated particles system is constant.
Reasion : Isolated system do not allow exchange of energy.
(a) Assertion is incorrect, reason is correct
(b) Assertion is correct, reason is incorrect
(c) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(d) Assertion is correct, reason is correct; reason is a correct explanation for assertion.

Answer: A

Question. The temperature of 5 moles of a gas which was held at constant volume was changed from 100º to 120ºC. The change in the internal energy of the gas was found to be 80 joule, the total heat capacity of the gas at constant volume will be equal to
(a) 4.0 joule per K
(b) 0.4 joule per K
(c) 8 joule per K
(d) None of these

Answer: A

Question.  A Carnot freezer takes heat from water at 0°C inside it and rejects it to the room at a temperature of 27°C. The latent heat of ice is 336 × 103 J kg–1. If 5 kg of water at 0°C is converted into ice at 0°C by the freezer, then the energy consumed by the freezer is close to :
(a) 1.67 × 10⁵ J
(b) 1.51 × 10⁵ J
(c) 1.71 × 10⁷ J
(d) None of these

Answer: A

Question.  The pressure of a monoatomic gas increases linearly from 4 × 10⁵ N/m² to 8 × 10⁵ N/m² when its volume increases from 0.2 m³ to 0.5 m³. The work done by the gas and increase in internal energy are given by
(a) 1.8 × 10⁵ J, 4.8 × 10⁵ J
(b) 1.8 × 10⁵ J, 1.8 × 10⁵ J
(c) 4.8 × 10⁵ J, 4.8 × 10⁵ J
(d) 4.8 × 10⁵ J, 1.8 × 10⁵ J

Answer: A

Question.  A Carnot engine whose low temperature reservoir is at 7°C has an efficiency of 50%. It is desired to increase the efficiency to 70%. By how many degrees should the temperature of the high temperature reservoir be increased?
(a) 380 K
(b) 560 K
(c) Both
(d) None of these

Answer: A

Question.  When 1 kg of ice at 0°C melts to water at 0°C, the resulting change in its entropy, taking latent heat of ice to be 80 cal/°C, is
(a) None of these
(b) 253 cal/K
(c) 273 cal/K
(d) 263 cal/K

Answer: A