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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.
| 251. |
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 | |
| 252. |
The efficiency gain follows the law of diminishing return with the increase in the number of heaters. |
| A. | true |
| B. | false |
| Answer» B. false | |
| 253. |
For storing a gas which one of the following types of compression will beideal |
| A. | constant volume |
| B. | polytropic |
| C. | adiabatic |
| D. | isothermal |
| Answer» E. | |
| 254. |
The efficiency of the Carnot cycle may beincreased by |
| A. | increasing the highesttemperature |
| B. | decreasing the highesttemperature |
| C. | increasing the lowesttemperature |
| D. | decreasing the lowesttemperature |
| Answer» E. | |
| 255. |
Tds equation is |
| A. | tds=cvdt + t |
| B. | b) |
| C. | c) |
| D. | d) |
| Answer» B. b) | |
| 256. |
During a throttling process |
| A. | exchange of heat doesnot take place |
| B. | expandingsteam does nowork |
| C. | internal energy of steamdoes not change |
| D. | all of the above |
| Answer» E. | |
| 257. |
In an ideal gas the partial pressure of a component is |
| A. | inversely proportional to the square of the molefraction |
| B. | directly proportional to the mole fraction |
| C. | inversely proportional to the mole fraction |
| D. | equal to the mole fraction |
| Answer» C. inversely proportional to the mole fraction | |
| 258. |
a heat engine receives heat at the rate of 1500 kJ/min.& gives an output of 8.2 kW. Its thermal efficiency is equal to |
| A. | 20.5 % |
| B. | 30.2% |
| C. | 32.8% |
| D. | 44.6% |
| Answer» D. 44.6% | |
| 259. |
The maximum percentage gain in Regenerative feed heating cycle thermal effciency |
| A. | increases with number of feed heaters increasing |
| B. | decreases with number of feed heaters increasing |
| C. | remains same unaffected by number of feed heaters |
| D. | none of the above |
| Answer» B. decreases with number of feed heaters increasing | |
| 260. |
In the Mollier diagram, the constant pressure lines diverge from one another. |
| A. | true |
| B. | false |
| Answer» B. false | |
| 261. |
15 = 6.19 J/K. |
| A. | 0.419 j/k |
| B. | 0.519 j/k |
| C. | 0.619 j/k |
| D. | 0.719 j/k |
| Answer» C. 0.619 j/k | |
| 262. |
Which law of thermodynamics definesentropy |
| A. | first |
| B. | second |
| C. | third |
| D. | zeroeth |
| Answer» C. third | |
| 263. |
A heat engine using lake water at 12° C as source & the surrounding atmosphere at 2°C as sink executes 1080 cycles per min. If the amount of heat drawn per cycle is 57J, then the output of the engine will be |
| A. | 66 w |
| B. | 56 w |
| C. | 46 w |
| D. | 36 w |
| Answer» E. | |
| 264. |
The latent heat ofvapouristation 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 | |
| 265. |
A system is said to be in thermodynamicequilibrium if it is in |
| A. | chemical equilibrium |
| B. | thermal equilibrium |
| C. | mechanical equilibrium |
| D. | all of the above |
| Answer» E. | |
| 266. |
Humidity ratio is given by the ratio of |
| A. | (mass of dry air per unit mass of water vapour)^2 |
| B. | 1/(mass of dry air * mass of water vapour) |
| C. | water vapour mass per unit mass of dry air |
| D. | mass of dry air per unit mass of water vapour |
| Answer» D. mass of dry air per unit mass of water vapour | |
| 267. |
Entropy of the universe |
| A. | tends to zero |
| B. | tends to a minimum |
| C. | tends to a maximum |
| D. | none of the above |
| Answer» D. none of the above | |
| 268. |
If the temperature of the source is increased, the efficiency of the Carnotengine |
| A. | decrease |
| B. | increase |
| C. | does not change |
| D. | will be equal to the efficiency of a practicalengine |
| Answer» C. does not change | |
| 269. |
Isothermal, isobaric, isochoric & adiabatic processes, under ideal condition, are ….Processes |
| A. | thermodynamic |
| B. | stable |
| C. | dynamic |
| D. | quasi-static |
| Answer» E. | |
| 270. |
Above critical point, asubstance exists as |
| A. | vapour |
| B. | liquid |
| C. | gas |
| D. | supersaturated fluid |
| Answer» E. | |
| 271. |
The efficiency of theCarnot cycle may be increased by |
| A. | decreasing the lowest temperature |
| B. | increasing the lowest temperature |
| C. | increasing the highest temperature |
| D. | both a & c |
| Answer» E. | |
| 272. |
……… is the ratio of actual cycle efficiency to that of the ideal cycle efficiency |
| A. | efficiency ratio |
| B. | work ratio |
| C. | effectiveness |
| D. | none of the above |
| Answer» B. work ratio | |
| 273. |
Which one of the following processes orsystems does not involve heat |
| A. | steady processes |
| B. | isothermal processes |
| C. | adiabatic processes |
| D. | thermal processes |
| Answer» D. thermal processes | |
| 274. |
The third law of thermodynamics |
| A. | defines entropy |
| B. | provides a base from which entropy is measured |
| C. | defines change of entropy |
| D. | gives availability of heat for conversion into work |
| Answer» E. | |
| 275. |
Considerfollowing options for a simple Rankine cyclei) increasing pressure at exist of turbine ii) increasing average temperature of heat additioniii) decreasing pressure at exit of turbine iv) 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. | |
| 276. |
The same volume of all gases at same temperatureand pressure wouldrepresent their |
| A. | specific gravity |
| B. | densities |
| C. | specific weights |
| D. | molecular weights |
| Answer» E. | |
| 277. |
Irreversibility can be distinguished in how many types? |
| A. | 0 |
| B. | 1 |
| C. | 2 |
| D. | 3 |
| Answer» D. 3 | |
| 278. |
A process becomes irreversible due to |
| A. | work performed by thesystem |
| B. | work performed uponthe system |
| C. | heat supplied to the system |
| D. | friction in the system |
| Answer» E. | |
| 279. |
A gas can never be liquid |
| A. | above criticaltemperature |
| B. | when it is diatomic |
| C. | when it is impure |
| D. | above roomtemperature |
| Answer» B. when it is diatomic | |
| 280. |
The limitation of the first law is |
| A. | does not indicate the possibility of a spontaneous process proceeding in a definite direction |
| B. | it assigns a quality to different forms of energy |
| C. | indicates the direction of any spontaneous process |
| D. | none of the mentioned |
| Answer» B. it assigns a quality to different forms of energy | |
| 281. |
For a reversible adiabatic process, thechange in entropy is |
| A. | zero |
| B. | minimum |
| C. | maximum |
| D. | infinite |
| Answer» B. minimum | |
| 282. |
In a carnot engine, when the working substance gives heat to the sink |
| A. | the temperature of the sink increases |
| B. | the temperature of the sink remains the same |
| C. | the temperature of the source decreses |
| D. | the temperature of the source decrease |
| Answer» C. the temperature of the source decreses | |
| 283. |
The index of compression n tends to reach ?(ratio of specific heats) |
| A. | when process is isothermal |
| B. | when process is isentropic |
| C. | when process is isentropic & specific heat does not change with temperature |
| D. | when flow is uniform & steady |
| Answer» D. when flow is uniform & steady | |
| 284. |
Which among this is not an exothermic reaction? |
| A. | combustion reaction |
| B. | neutralization reaction |
| C. | thermite reaction |
| D. | evaporating liquid water |
| Answer» E. | |
| 285. |
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 | |
| 286. |
A perfect gas having p1= 0.1 M/mm², v1=0.18 m³, T1=20°C is compressed to 1/10 of volume in an isothermal process.The change in entropy is |
| A. | -141.45 j/k |
| B. | 141.45 j/k |
| C. | -41446.23 j/k |
| D. | 0 |
| Answer» C. -41446.23 j/k | |
| 287. |
1.6 Kg of air is expanded at constant pressure from 100°C to 0°C resulting in entropy change of - 2.0 J/K 3.2 Kg of air is cooled at constant volume from 100°C to 0°C with a change in entropy of -3.0 J/K.The ratio Cp/ Cv is |
| A. | 1.333 |
| B. | 1.366 |
| C. | 1.4 |
| D. | 1.43 |
| Answer» D. 1.43 | |
| 288. |
Which of the following remains constant during an adiabatic expansion |
| A. | entropy |
| B. | temperature |
| C. | internal energy |
| D. | none of the above |
| Answer» B. temperature | |
| 289. |
Which statement is wrong for throttlingexpansion |
| A. | pressure drop = 0 |
| B. | change in enthalpy = 0 |
| C. | work done = 0 |
| D. | change in internalenergy = 0 |
| Answer» D. change in internalenergy = 0 | |
| 290. |
If water is injected into a container with has unsaturated air, |
| A. | water will evaporate |
| B. | moisture content of air will decrease |
| C. | pw will decrease |
| D. | all of the mentioned |
| Answer» B. moisture content of air will decrease | |
| 291. |
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. | |
| 292. |
The greater the temperature, the is the vapour pressure. |
| A. | lower |
| B. | higher |
| C. | depends on the substance |
| D. | none of the mentioned |
| Answer» C. depends on the substance | |
| 293. |
In a reversible adiabatic process headadded is equal to |
| A. | zero |
| B. | positive value |
| C. | c) |
| D. | d) |
| Answer» B. positive value | |
| 294. |
The final temperatures of two bodies, initially at T1 and T2 can range from |
| A. | (t1-t2)/2 to sqrt(t1*t2) |
| B. | (t1+t2)/2 to sqrt(t1*t2) |
| C. | (t1+t2)/2 to (t1*t2) d) (t1-t2)/2 to (t1*t2) |
| Answer» C. (t1+t2)/2 to (t1*t2) d) (t1-t2)/2 to (t1*t2) | |
| 295. |
According to kinetic theory of heat |
| A. | temperature should rise during boiling |
| B. | temperature should fall during freezing |
| C. | at low temperature all bodies are in solid state |
| D. | at absolute zero there is absolutely no vibration ofmolecules |
| Answer» E. | |
| 296. |
Efficiency of Rankine cycle is function of |
| A. | highest temperature of cycle |
| B. | lowest temperature of cycle |
| C. | both highest & lowest temperature of the cycle |
| D. | none of the above |
| Answer» D. none of the above | |
| 297. |
The main advantage of a Reheat Rankine cycle is |
| A. | reduced moisture content in l.p side of turbine |
| B. | increased efficiency |
| C. | increased work of turbine |
| D. | reduced load on condenser |
| Answer» B. increased efficiency | |
| 298. |
The temperature in a process in which work is done by expanding a gas underadiabatic condition will |
| A. | decrease |
| B. | increase |
| C. | first decrease & then increase |
| D. | remain unaltered |
| Answer» B. increase | |
| 299. |
In which of the following processes thechange in internal energy of a gas is equal to the work done |
| A. | adiabatic process |
| B. | isothermal process |
| C. | constant volume process |
| D. | constant pressure process |
| Answer» B. isothermal process | |
| 300. |
The perpetual motion of the first kind is represented by which of the following? |
| A. | a machine that continuously creates itsown energy |
| B. | an engine with 100 percent efficiency |
| C. | a fully reversible engine |
| D. | none of the above |
| Answer» B. an engine with 100 percent efficiency | |