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

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.

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

A Carnot engine, having an efficiency of as 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

The ratio of the specific heats  in terms of degrees of freedom (n) is given by

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

A refrigerator works between 4^o C and 30^o 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

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

• 24 g

• 31.5 g

• 42.5 g

• 42.5 g

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

• 45^o C

• 20^o C

• 42^o C

• 42^o C

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 ),

• 64 p

• 32 p

• 
•