Thermodynamics

An ice box made of Styrofoam (Thermal conductivity = 0.01 Jm^-1 s^-1 K^-1) is used to keep liquids cool. It has a total wall area including lid of 0.8 m² and wall thickness of 2.0cm. A bottle of water is placed in box and filled with ice. If the outside temperature is 30°C, the rate of flow of heat into the box is ( in J s^-1)

• 16

• 14

• 12

• 10

During an adiabatic process, the volume of a gas is found to be proportional to the cube of its absolute temperature. The ratio C_p / C_V for the gas is

• 5/3

• 4/3

• 3/2

• 5/4

The work done by a gas is maximum when it expands

• isothermally

• adiabatically

• isentropically

• isobarically

An ideal monoatomic gas at 27°C is compressed adiabatically to 8/27 times of its present volume. The increase in temperature of the gas is

• 375°C

• 402°C

• 175°C

• 475°C

Blowing air with open mouth is an example of

• isobaric process

• isochoric process

• isothermal process

• adiabatic process

An ideal gas heat engine operates in a Carnot's cycle between 227°C and 127°C. It absorbs 6 x 10⁴ J at high temperature. The amount of heat converted into work is

• 1.6 × 10⁴ J

• 1.2 × 10⁴ J

• 4.8 × 10⁴ J

• 3.5 × 10⁴ J

A monoatomic gas is suddenly compressed to (1/8) of its initial volume adiabatically. The ratio of its final pressure to the initial pressure is : (Given the ratio of the specific heats of the given gas to be 5/3)

• 32

• 40/3

• 24/5

• 8

A Carnot engine takes heat from a reservoir at 627° C and rejects heat to a sink at 27°C. Its efficiency will be

• 3/5

• 1/3

• 2/3

• 200/209

During an adiabatic process, the cube of the pressure is found to be inversely proportional to the fourth power of the volume. Then the ratio of specific heats is

• 1

• 1.33

• 1.67

• 1.4

A Carnot's engine operates with source at 127°C and sink at 27°C. If the source supplies 40 kJ of heat energy, the work done by the engine is

• 30 kJ

• 10 kJ

• 4 kJ

• 1 kJ