Steam at 100o C is passed into 20 g of water at 10o C. When the

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 Multiple Choice QuestionsMultiple Choice Questions

71.

A Carnot's engine is made to work between 200°C and 0°C first and then between 0°C and − 200°C. The ratio of efficiencies of the engine in the two cases is

  • 1 : 1.73

  • 1.73 : 1

  • 1 : 2

  • 1 : 1


72.

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 its half. Then,

  • compressing the gas through adiabatic process will require more work to b done

  • compressing the gas through isothermally or adiabatically will require the same amount of work.

  • which of the case (whether compression through isohermal or through adiabatic process) requires more work will depend upon the atomicity of the gas.

  • which of the case (whether compression through isohermal or through adiabatic process) requires more work will depend upon the atomicity of the gas.

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73.

A piece of ice falls from a height h so that it melts completely. Only one-quarter of the heat produced is absorbed by the ice and all energy of ice gets converted into heat during its fall. The value of h is [Latent heat of ice is 3.4 x 105 J/kg and g =10 N/kg]

  • 544 km

  • 136 km

  • 68 km

  • 68 km

4466 Views

74.

A Carnot engine, having an efficiency of asstraight eta space equals 1 over 10 heat engine, is used as a refrigerator. If the work is done on the system is 10J, the amount of energy absorbed from the reservoir at lower temperature is

  • 100J 

  • 99 J 

  • 90 J

  • 90 J

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75.

The ratio of the specific heats straight C subscript straight p over straight C subscript straight v space equals gamma in terms of degrees of freedom (n) is given by

  • open parentheses 1 plus 1 over straight n close parentheses
  • open parentheses 1 plus straight n over 3 close parentheses
  • open parentheses 1 plus 2 over straight n close parentheses
  • open parentheses 1 plus 2 over straight n close parentheses
1175 Views

76.

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 of heat is added to the system. The heat absorbed  by the system in the process AC will be

  • 380 J

  • 500 J

  • 460 J

  • 460 J

2777 Views

77.

A refrigerator works between 4o C and 30o 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)

  • 23.65 W

  • 236.5 W

  • 2365 W

  • 2365 W

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78.

Steam at 100o C is passed into 20 g of water at 10o C. When the water acquires a temperature of 80o C, the mass of water present will be,

  • 24 g

  • 31.5 g

  • 42.5 g

  • 42.5 g


D.

42.5 g

Heat lost by the steam = heat gained by water

Let, m' be the amount of heat converted into water.

m' x L = ms 
m' x 540 = 20 x 1 x (80 - 10)

m' = 
Therefore, net amount of water = 20 + 2.5 = 22.5 g

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79.

Certain quantity of water cools from 70o C to 60o C in the first 5 min and to 54o  C in the next 5 min. The temperature of the surroundings is,

  • 45o C

  • 20o C

  • 42o C

  • 42o C

1588 Views

80.

A monoatomic gas at a pressure p, having a volume V expands isothermally to a volume 16 V. The final pressure of the is (take straight gamma space equals space 5 over 3),

  • 64 p

  • 32 p

  • straight p over 64
  • straight p over 64
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