NEET Free Online Mock Test - 2019

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# NEET Physics  Thermodynamics  Practice Q & A

1. “Heat cannot by itself flow from a body at lower temperature to a body at higher temperature” is a statement or consequence of

 first law of thermodynamics second law of thermodynamics conservation of momentum conservation of mass

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2. Helium gas goes through a cycle ABCDA (consisting of two isochoric and isobaric lines) as shown in figure. Efficiency of this cycle is nearly
(Assume the gas to be close to ideal gas)

 15.4% 9.1% 10.5% 12.5%

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3. A Carnot engine, having an efficiency of η =1/10 as heat engine, is used as a refrigerator. If the work done on the system is 10 J, the amount of energy absorbed from the reservoir at lower temperature is

 100 J 99 J 90 J 1 J

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4. The specific heat capacity of a metal at low temperature (T) is given as Cp(kJK–1kg–1) = 32$\left(\dfrac{\text{T}}{400}\right)^3$. A 100 gram vessel of this metal is to be cooled from 20 K to 4 K by a special refrigerator operating at room temperature (27°C). The amount of work required to cool the vessel is

 Less than 0.028 kJ Equal to 0.002 kJ Greater than 0.148 kJ Between 0.148 kJ and 0.028 kJ

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5. A Carnot engine working between 300 K and 400 K has 800 J of useful work. The amount of heat energy supplied to the engine from the source is

 2400 J 3200 J 1200 J 3600 J

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6. Which statement is incorrect?

 All reversible cycles have same efficiency. Reversible cycle has more efficiency than an irreversible one. Carnot cycle is a reversible one. Carnot cycle has the maximum efficiency in all cycles.

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7. 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)

 236.5 W 2365 W 2.365 W 23.65 W

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8. A Carnot engine, whose efficiency is 40%, takes in heat from a source maintained at a temperature of 500K. It is desired to have an engine of efficiency 60%, then the intake temperature for the same exhaust (sink) temperature must be :

 efficiency of Carnot engine cannot be made larger than 50% 1200 K 750 K 600 K

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9. 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?