ISRO Mechanical Exam: Thermodynamics Quiz

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Question 1

Air with initial condition of p1, v1 expands to final condition of p1/2, 3v₁. The process is

• AHyperbolic
• BAdiabatic
• Cpolytropic with n>1
• Dpolytropic with n<1

Question 2

1 kg of moist air of RH 70% at 21 °C is cooled at constant pressure of 1 bar to 5 °C. The vapour pressure at 21 °C and 5 °C are 0.025 bar and 0.0087 bar.The percentage of water vapour that condenses into water, at 5 °C is

• A65.6%
• B85%
• C51%
• D17%

Question 3

A heat engine operates between a cold reservoir at temperature K and a hot reservoir at Temperature , it takes 200 J of heat from the hot reservoir and deliver 120 J of heat to the cold reservoir in a cycle. What will be the efficiency of the engine?

• A30 %
• B40 %
• C60 %
• D20 %

Question 4

A engine works on Carnot cycle between 727 °C and 227 °C. The efficiency of the engine is

• A50%
• B75.4%
• C31.2%
• D68.8%

Question 5

The ratio of specific heats of a gas is 1.4 and the value of specific heat at constant pressure is 7.0 cal/mole °C. The difference between specific heat at constant pressure and specific heat at constant volume will be (in cal/mole °C)

• A1.4
• B1.7
• C5.0
• D2.0

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