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This set of Thermodynamics Multiple Choice Questions & Answers (MCQs) focuses on Thermodynamics Set 3

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
  • Pulsejet
  • 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%
  • Pulsejet
  • 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
  • Pulsejet
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  • Part of the steam is withdrawn from the turbine and is utilised in heating the exhaust steam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  • Part of the steam is withdrawn from the turbine and is used in heating the steam being supplied to the turbine
  • Part of the steam is withdrawn from the turbine and is used in heating the feed water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
  • Pulsejet
  • 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
  • Pulsejet
  • 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
  • Pulsejet
  • 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
  • Pulsejet
  • 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
  • Pulsejet
  • 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
  • Pulsejet
  • 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
  • Pulsejet
  • Cetane number
  • Octane number