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MCQOPTIONS
This section includes 1092 Mcqs, each offering curated multiple-choice questions to sharpen your Mechanical Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 51. |
Gases could have an infinite number of specific heats but only . Specific heats are defined |
| A. | one |
| B. | two |
| C. | three |
| D. | four |
| Answer» C. three | |
| 52. |
The area under the T-s (temperature - entropy) curve of any thermodynamic process represents |
| A. | heat rejected only |
| B. | heat absorbed only |
| C. | work done during the process |
| D. | heat absorbed or rejected |
| Answer» E. | |
| 53. |
For storing a gas which one of the following types of compression will be ideal |
| A. | constant volume |
| B. | polytropic |
| C. | adiabatic |
| D. | isothermal |
| Answer» E. | |
| 54. |
Leaking of air from a punctured tube is an example of |
| A. | isothermal expansion |
| B. | adiabatic expansion |
| C. | throttling |
| D. | constant pressureexpansion |
| Answer» D. constant pressureexpansion | |
| 55. |
Consider the following statements: The definition of1. temperature is due to zeroth law of thermodynamics2. entropy is due to first law of thermodynamics3. internal energy is due to second law of thermodynamics4. reversibility is due to Kelvin-Planck's ststement of these statements |
| A. | 1,2 & 3 are correct |
| B. | 1,3 & 4 are correct |
| C. | 1 alone is correct |
| D. | 2 alone is correct |
| Answer» D. 2 alone is correct | |
| 56. |
In a reversible cycle, the source temperature is 227 C & the sink temperature is 27 C. The maximum available work for a heat input of 100 kJ will be |
| A. | 100 kj |
| B. | 60 kj |
| C. | 40 kj |
| D. | 88 kj |
| Answer» D. 88 kj | |
| 57. |
An engine receives 15152 J/s of heat & produces 5 KW of power. The efficiency of the engine is |
| A. | 25% |
| B. | 27.5% |
| C. | 30% |
| D. | 33% |
| Answer» B. 27.5% | |
| 58. |
The second law of thermodynamics defines |
| A. | heat |
| B. | enthalpy |
| C. | internal energy |
| D. | entropy |
| Answer» E. | |
| 59. |
Which law of thermodynamics defines entropy |
| A. | first |
| B. | second |
| C. | third |
| D. | zeroeth |
| Answer» C. third | |
| 60. |
A thermodynamic cycle operates between 400 K. & 290 K. 500 MJ/s of heat is added to the working substance. The power generated is |
| A. | 290 mw |
| B. | 290 mj |
| C. | 137.5 mw |
| D. | 137.5 mj |
| Answer» E. | |
| 61. |
A reversible engine performing as refrigerator has COP=33%. If the same machine operates as engine, its efficiency will be |
| A. | 67% |
| B. | 33% |
| C. | 75% |
| D. | 37.5% |
| Answer» B. 33% | |
| 62. |
Turbine blade efficiency reduces in a Rankine cycle if |
| A. | heat supply in boiler increases |
| B. | heat supply in boiler decreases |
| C. | condenser pressure decreases |
| D. | condenser pressure increases |
| Answer» D. condenser pressure increases | |
| 63. |
First law of thermodynamics gives relationship between which of the following? |
| A. | heat & internal energy |
| B. | heat & work |
| C. | heat, work & properties of the system |
| D. | various thermodynamics processes |
| Answer» D. various thermodynamics processes | |
| 64. |
Which of the following statements, regarding a property of system, is correct? |
| A. | it is path function |
| B. | it is a point function |
| C. | it is always of intensive type |
| D. | none of the above |
| Answer» C. it is always of intensive type | |
| 65. |
The temperature of feed water can be increased in following two ways in a regenerative Rankine cyclei) by passing feed water around turbine casing in direction opposite to flow of steamii) by bleeding certain portion of steam at the end of h.p expansion & mixing with condensate to make feed water at the temperature of boiler |
| A. | i) is preferred over ii) for higher efficiency |
| B. | ii) is preferred over i) for reduced moisture content of steam in l.p side |
| C. | only i) is implemented in actual practice |
| D. | by preferring ii) overi) significant gain in efficiency results |
| Answer» C. only i) is implemented in actual practice | |
| 66. |
Correlate the following statementsi) the volume of water into which steam is condensed in condenser is very much smaller than the volume of steam before condensationii) the net work of a Rankine cycle is heat supplied in boiler - heat rejected to condenser - pump work |
| A. | both i) & ii) are correct, i) is the correct reason for ii) |
| B. | i) & ii) are correct, ii) is the correct interpretation if i) |
| C. | both i) & ii) are not correct |
| D. | both i) & ii) are independently correct |
| Answer» E. | |
| 67. |
The flow through turbine on a Mollier chart is represented by |
| A. | vertical line |
| B. | horizontal line |
| C. | curved line convex up |
| D. | curved line convex down |
| Answer» B. horizontal line | |
| 68. |
A system is said to be in thermodynamic equilibrium if it is in |
| A. | chemical equilibrium |
| B. | thermal equilibrium |
| C. | mechanical equilibrium |
| D. | all of the above |
| Answer» E. | |
| 69. |
Examine follwing two statements & choosethe correct relationshipi) for a steam power plant Rankine cycle is preferred over Carnot cycleii) a pump which will handle the mixture of vapour & liquid is difficult to construct |
| A. | both i) ii) are correct & i) is the consequence of ii) |
| B. | both i) & ii) are independently correct |
| C. | i) is correct but ii) is not |
| D. | ii) is correct but i) is not |
| Answer» B. both i) & ii) are independently correct | |
| 70. |
A regenerative Rankine cycle may approach efficiency of a Carnot cycle between same temperature by |
| A. | reducing heat to condenser |
| B. | reducing volume of steam passed into condenser |
| C. | increasing turbine work |
| D. | adding heat a highest temp. |
| Answer» E. | |
| 71. |
A Rankine cycle is less efficient than Carnot cycle because |
| A. | the working fluid is steam |
| B. | heat is not added athighest temperature of cycle |
| C. | condensation processis extended into liquid phase |
| D. | superheating occurs at constant pressure |
| Answer» C. condensation processis extended into liquid phase | |
| 72. |
Triple point of a pure substance is a point at which |
| A. | solid & vapour exist together |
| B. | solid & liquid exist together |
| C. | liquid & vapour exist together |
| D. | solid, liquid & vapour phases existtogether |
| Answer» E. | |
| 73. |
Considerfollowing options for a simple Rankine cyclei) increasing pressure at exist of turbineii) increasing average temperature of heat additioniii) decreasing pressure at exit of turbineiv) superheating of steamv) decreasing pressure during superheating. Which combination of above will increase Rankine efficiency? |
| A. | i), ii) & iv) |
| B. | i), ii) & v) |
| C. | iii), iv) & v) |
| D. | ii), iii) & iv) |
| Answer» E. | |
| 74. |
As differentials, heat & work would be described mathematically as |
| A. | exact |
| B. | inexact |
| C. | point function |
| D. | discontinuity |
| Answer» C. point function | |
| 75. |
Which of the following is an open thermodynamic system? |
| A. | pressure cooker |
| B. | manual ice cream freezer |
| C. | centrifugal pump |
| D. | none of the above |
| Answer» D. none of the above | |
| 76. |
The latent heat of vapouristation at critical point is |
| A. | less than zero |
| B. | greater than zero |
| C. | equal to zero |
| D. | none of the above |
| Answer» D. none of the above | |
| 77. |
The latent enthalpy of vapourisation at critical point is |
| A. | zero |
| B. | minimum |
| C. | maximum |
| D. | none of the above |
| Answer» B. minimum | |
| 78. |
The gas laws can be used with minimum error is case of |
| A. | wet steam |
| B. | dry steam |
| C. | saturated steam |
| D. | superheated steam |
| Answer» E. | |
| 79. |
at 1 atm and 27oC? |
| A. | 23.4 liter |
| B. | 37.5 liter |
| C. | 42.1 liter |
| D. | 59.6 liter view answer |
| Answer» B. 37.5 liter | |
| 80. |
Temperature of a gas is produced due to which of the following? |
| A. | attraction of molecules |
| B. | repulsion of molecules |
| C. | kinetic energy of molecules |
| D. | all of the above |
| Answer» D. all of the above | |
| 81. |
Which of the following cycles is used in thermal power plants? |
| A. | brayton |
| B. | carnot |
| C. | ericsson |
| D. | rankine |
| Answer» E. | |
| 82. |
Most of the fossil fuel based power plants operate on |
| A. | rankine cycle |
| B. | brayton cycle |
| C. | carnot cycle |
| D. | either rankine or brayton cycle |
| Answer» E. | |
| 83. |
Essential parts of a power plant operating on a Rankine cycle are |
| A. | engine or turbine |
| B. | engine or turbine & conderser |
| C. | gine or turbine, condenser, pump &boiler |
| D. | engine or turbine & boiler |
| Answer» D. engine or turbine & boiler | |
| 84. |
In an unsaturated air the state of a vapour is |
| A. | wet |
| B. | superheated |
| C. | saturated |
| D. | unsaturated |
| Answer» C. saturated | |
| 85. |
Higher dryness fraction of steam at turbine exit in a Rankine cycle |
| A. | will increase cycle efficiency |
| B. | will increase turbine work |
| C. | will protect turbine blading |
| D. | will reduce pump work |
| Answer» D. will reduce pump work | |
| 86. |
Correlate the following statementsi) by reducing the condenser pressure in a Rankine cycle work output is increasedii) increased proportion of moisture in turbine is undesirable because water particles erode the blades |
| A. | both i) & ii) are independently true |
| B. | both i) & ii) are not true |
| C. | i) is true but ii) is not |
| D. | ii) is true but i) is not |
| Answer» B. both i) & ii) are not true | |
| 87. |
In which of the following processes the external work done is not zero? |
| A. | throttling |
| B. | free expansion |
| C. | constant volume process |
| D. | constant pressureprocess |
| Answer» E. | |
| 88. |
The temperature in a process in which work is done by expanding a gas under adiabatic condition will |
| A. | decrease |
| B. | increase |
| C. | first decrease & then increase |
| D. | remain unaltered |
| Answer» B. increase | |
| 89. |
In a reheat Rankine cycle steam with enthalpy of 3300 kJ/kg is expanded in h.p turbine to a state where enthalpy is 2650 kJ/kg. The steam is further expnaded from a state where enthalpy is 2950 kJ/kg to enthalpy of 2525 kJ/kg & latent heat of 2201 kJ.kg. The work of the cycle & amount of reheat respectively are |
| A. | 1075 kj/kg,300 kj.kg |
| B. | 1399 kj/kg, 300 kj/kg |
| C. | 1075 kj/kg, 324 kj/kg |
| D. | 1399 kj/kg, 324 kj/kg |
| Answer» B. 1399 kj/kg, 300 kj/kg | |
| 90. |
Consider the following statements regarding superheating in Rankine Cycles1. It reduces the specific steam consumption2. It increases the dryness fraction of steam at the exhaust for the same value of condenser pressure3. It reduces the cycle efficiency Of the these statements |
| A. | 1 & 2 are correct |
| B. | 2 & 3 are correct |
| C. | 1 & 3 are correct |
| D. | 1, 2 & 3 are correct |
| Answer» B. 2 & 3 are correct | |
| 91. |
Which of the following is used as a working substance for a Carnot cycle? |
| A. | ideal gas |
| B. | real gas |
| C. | steam |
| D. | atmospheric air |
| Answer» B. real gas | |
| 92. |
Above critical point, a substance exists as |
| A. | vapour |
| B. | liquid |
| C. | gas |
| D. | supersaturated fluid |
| Answer» E. | |
| 93. |
Mathematically a pure substance can be written as |
| A. | p=f(t,v) |
| B. | v= f(p,t) |
| C. | t=f(p,v) |
| D. | any of the above |
| Answer» E. | |
| 94. |
A Carnot cycle operates between source & sink temperatures of 250 C & - 15 C. If the system receives 90kJ from the source then the net work transfer equals |
| A. | 30.5 kj |
| B. | 35.65 kj |
| C. | 45.54 kj |
| D. | 65.54 kj |
| Answer» D. 65.54 kj | |
| 95. |
A power cycle using steam as working fluid consist ofi) constant pressure heat additionii)adiabatic expansioniii) constant pressure heat rejection &iv) adiabatic compression. The cycle is |
| A. | simple rankine cycle |
| B. | modified rankine cycle |
| C. | carnot cycle |
| D. | regenerative rankine cycle |
| Answer» D. regenerative rankine cycle | |
| 96. |
In a simple Rankine cycle steam was expanded from 100 bar & 380 C to 1 bar 0.8 dry state. The pump motor consumes 10 kJ/kg of energy. The efficiency of cycle is |
| A. | 31% |
| B. | 34% |
| C. | 29.8% |
| D. | 30.6% |
| Answer» E. | |
| 97. |
The same volume of all gases at same temperatureand pressure would represent their |
| A. | specific gravity |
| B. | densities |
| C. | specific weights |
| D. | molecular weights |
| Answer» E. | |
| 98. |
In all irrevesible processes, the entropy of the system |
| A. | remains unaltered |
| B. | reduces to zero |
| C. | increases |
| D. | none of the above |
| Answer» D. none of the above | |
| 99. |
Air with initial condition of p1, v1 expands to final condition of p1/2, 3v1. The process is |
| A. | hyperbolic |
| B. | adiabatic |
| C. | polytropic with n > 1 |
| D. | polytropic with n < 1 |
| Answer» B. adiabatic | |
| 100. |
In a cyclic heat engine operating between a source temperature of 600 C & a sink temperature of 20 C, the least rate of heat rejection per kW net output of the engine is |
| A. | 0.460 kw |
| B. | 0.505 kw |
| C. | 0.588 kw |
| D. | 0.650 kw |
| Answer» C. 0.588 kw | |