Thermodynamics Set 3 MCQs

Q1 | In the polytropic process equation pvn = constant, if the value of n is infinitely large the process is termed as

Adiabatic

Constant volume

Isothermal

Constant pressure

Constant temperature

Q2 | The ratio of the rise in temperature of a gas when compressed adiabatically to that when compressed isothermally to the same extent is

More than 1

Less than 1

Equal to 1

Depends on the gas

None of the above

Q3 | Other factors remaining constant, if the temperature of sink is increased, the efficiency of the Carnot engine will

increase or decrease depending upon temperature ratio

will not change

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increase

decrease

Q4 | One of the most efficient engines ever developed operates between 2100 k and 700 k. Its actual efficiency is 40%. What percentage of its maximum possible efficiency is this?

40%

33.30%

60%

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66.67%

Q5 | For any reversible process, the change in entropy of the system and surroundings is

Negative

Zero

Unity

Infinite

Positive

Q6 | If all the variables of a steam are in-dependent of time it is said to be in

Unsteady flow

Uniform flow

Steady flow

Closed flow

Constant flow

Q7 | Entropy of mixing is always

positive

Zero

Negative

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Q8 | A system comprising a single phase is called a

Open system

Isolated system

Closed system

Homogeneous system

Heterogeneous system

Q9 | An open system

Is a specified region where transfers of energy and/or mass take place

Is a region of constant mass and only energy is allowed to cross the boundaries

Cannot transfer either energy or mass to or from the surroundings

Has a mass transfer across its boundaries, and the mass within the system is not necessarily constant

None of the above

Q10 | In the regenerative cycle

Power is generated in two stages

Part of the steam is withdrawn from the turbine and is utilised in heating the exhaust steam

Steam is reheated after expansion and again used

Part of the steam is withdrawn from the turbine and is used in heating the steam being supplied to the turbine

Part of the steam is withdrawn from the turbine and is used in heating the feed water

Q11 | Which of the following is a path function quantity?

Work done

Pressure

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Temperature

Enthalpy

Q12 | An ordinary mercury thermometer can be used for temperatures about

200?C

400?C

300?C

100?C

500?C

Q13 | Triple point

Occurs in sublimation

Occurs in a mixture of two or more gases

Is the range of temperature within which three constituents simultaneously change phase

Is that point where three phases solid, liquid and gas exist together

None of the above

Q14 | The characteristics of a control volume are

The volume shape and position with respect to an observer may change

The volume shape and position with respect to an observer are fixed

There is no material flow across the boundary

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There is material flow across the boundary

Q15 | The gas turbine works on

Rankine cycle

Brayton cycle

Erricson cycle

Otto cycle

Carnot cycle

Q16 | All of the following are intensive properties EXCEPT

Viscosity

Mass

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Density

Temperature

Q17 | A body of weight 100 N falls freely through a distance of 10 m against an atmospheric drag force of 5 N. Considering the body as the system, the work interaction is

1000 Nm

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1050 Nm

50 Nm

950 Nm

Q18 | In a steam turbine when steam expands, the entropy

Decreases exponentially

Does not change

Increases exponentially

Decreases linearly

Increases linearly

Q19 | Of the following first law statements, choose the one that is wrong

the net heat transfer equals the network for a cycle

the heat transfer equals the work plus the energy change

the heat transfer cannot exceed the work done

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the energy of an isolated system remains constant

Q20 | If the dryness fraction of a sample by throttling calorimeter is 0.8 and that by separating calorimeter is also 0.8, then the actual dryness fraction of sample will be taken as

Volume change is negligible

1

0.8

0.5

0.64

Q21 | Work done by an expanding gas under adiabatic condition results in

Temperature decrease

Temperature decreases first and then increase

Temperature increase first and then decrease

No change in temperature

Temperature increase

Q22 | Carburetted water gas is obtained by

heating water at high temperature in a copper vessel

Burning oil

spraying oil into a carburettor filled with hot brick elieckar work through which the gases pass

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Passing alternately steam and air through while hot carbon

Q23 | A process which does not dissipate available energy is known as

Isothermal process

Energyless process

Adiabatic process

Ideal process

Frictionless process

Q24 | The weight of 1 cu-m of carbon dioxide at NTP if the characteristic gas constant is 19.28 kg metre/kg/?C, would be

3.924 kg

2.5 kg

1.962 kg

1 kg

1.5 kg

Q25 | The ability of gasoline to resist detonation during combustion is given by

iso-octane number

heptane number

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Cetane number

Octane number