McqMate
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Mechanical Engineering .
| 351. |
An elastic sphere of 0.5 m diameter contains a gas at 115 k Pa. Heating of the sphere causes it to increase to 0.62 m and during the process the pressure is proportional to the sphere diameter. The work done by the gas will be |
| A. | 7.7 kJ |
| B. | Pulsejet |
| C. | 9.9 kJ |
| D. | 15 kJ |
| E. | 11 kJ |
| Answer» A. 7.7 kJ | |
| 352. |
Second law of theromodynamics defines |
| A. | Heat |
| B. | Entropy |
| C. | Work |
| D. | Internal energy |
| E. | Enthalpy |
| Answer» B. Entropy | |
| 353. |
In a reversible polytropic process |
| A. | The entropy remains constant |
| B. | Enthalpy remains constant |
| C. | Internal energy remains constant |
| D. | Some heat transfer occurs |
| E. | Temperature remains constant |
| Answer» D. Some heat transfer occurs | |
| 354. |
Entropy of the universe tends to |
| A. | Approximately zero |
| B. | A minimum |
| C. | A maximum |
| D. | No particular value as it remains constant |
| E. | Zero |
| Answer» C. A maximum | |
| 355. |
Isothermals are curves obtained by drawing |
| A. | P against T |
| B. | P against V |
| C. | V against T |
| D. | PV against T |
| E. | PV against V |
| Answer» B. P against V | |
| 356. |
In an isothermal expansion of gases |
| A. | Temperature is lowered |
| B. | Temperature shows the extent of expansion |
| C. | Temperature becomes zero |
| D. | Temperature is unaltered |
| E. | Temperature is raised |
| Answer» D. Temperature is unaltered | |
| 357. |
A machine that continuously creates its own energy is known as |
| A. | Perpetual motion machine of second kind |
| B. | Self-propelled machine |
| C. | 100% efficient machine |
| D. | Perpetual motion machine of first kind |
| E. | Reversible machine |
| Answer» D. Perpetual motion machine of first kind | |
| 358. |
When a direct current is passed through a junction of two dissimilar metals, the junction becomes either cold or hot. The phenomenon is known as |
| A. | Faraday's law |
| B. | Peltier's effect |
| C. | Thompson effect |
| D. | Maxwell's effect |
| E. | Seeback's effect |
| Answer» B. Peltier's effect | |
| 359. |
Brayton cycle cannot be used in reciprocating engines even for same adiabatic compression ratio and work output because |
| A. | Brayton cycle is for slow speed engines |
| B. | Brayton cycle is less efficient |
| C. | Brayton cycle requires large air-fuel ratio |
| D. | Otto cycle is more efficient |
| E. | Large volume of low pressure air cannot be efficiently handled in reciprocating engines |
| Answer» E. Large volume of low pressure air cannot be efficiently handled in reciprocating engines | |
| 360. |
Which of the following relations is not valid during throttling process? |
| A. | External work done = Zero |
| B. | Total heat = Constant |
| C. | Pressure drop = Zero |
| D. | Change in enthalpy = Zero |
| E. | Change in internal energy = Zero |
| Answer» C. Pressure drop = Zero | |
| 361. |
Two ideal engines A and B have their sources at 600 k and 400 k and their sinks at 300 k and 250 k respectively. What inference can be drawn about their efficiency |
| A. | A is more efficient than B |
| B. | A is less efficient than B |
| C. | The information given is incomplete |
| D. | Both are equally efficient |
| E. | Pulsejet |
| Answer» A. A is more efficient than B | |
| 362. |
A law which is applicable only to ideal vapours and liquids, that equates the equilibrium partial pressures of a solution component in the coexisting phases, is known as |
| A. | Maxwell's equation |
| B. | Roult's law |
| C. | Henry's law |
| D. | Fick's law |
| E. | Joule's law |
| Answer» B. Roult's law | |
| 363. |
A barn is |
| A. | A unit of area |
| B. | A unit of length |
| C. | A unit of time |
| D. | A unit of mass |
| E. | None of the above |
| Answer» A. A unit of area | |
| 364. |
Highly polished surfaces of a thermosflask prevent heat by |
| B. | Convection |
| C. | Radiation |
| D. | Conduction |
| E. | microns |
| Answer» C. Radiation | |
| 365. |
As we go up in air the temperature of air decreases because |
| A. | Pulsejet |
| B. | winds help in heat transfer by convection |
| C. | of low pressure of air |
| D. | oxygen content of air decreases sharply |
| E. | heating effect due to infra red radiations from the surface of the earth is reduced |
| Answer» E. heating effect due to infra red radiations from the surface of the earth is reduced | |
| 366. |
According to kinetic theory of heat |
| A. | Temperature should rise during boiling |
| B. | Temperature should fall during freezing |
| C. | At low temperatures all bodies are in solid state |
| D. | At absolute zero there is absolute no vibration of molecules |
| E. | None of the above |
| Answer» D. At absolute zero there is absolute no vibration of molecules | |
| 367. |
Balanced draft incorporates |
| A. | Forced draft |
| B. | Induced draft |
| C. | Forced and induced draft |
| D. | Chimney draft only |
| E. | None of the above |
| Answer» C. Forced and induced draft | |
| 368. |
The internal energy of an ideal gas is |
| A. | A function of temperature alone |
| B. | A function of pressure |
| C. | A function of volume |
| D. | (a) and (b) only |
| E. | All the above |
| Answer» A. A function of temperature alone | |
| 369. |
In any process the maximum amount of mechanical energy that can be converted to heat |
| A. | Depends upon the intake and exhaust temperature |
| B. | Is 50% |
| C. | Depends upon the amount of friction |
| D. | Depends upon whether kinetic energy is involved |
| E. | Is 100% |
| Answer» E. Is 100% | |
| 370. |
The characteristic equation of gases pv = nRT holds good for |
| A. | Real gases |
| B. | Monoatomic gases |
| C. | Diatomic gases |
| D. | Ideal gases |
| E. | Mixture of gases |
| Answer» A. Real gases | |
| 371. |
The external work donw is zero all the following cases EXCEPT |
| A. | Pulsejet |
| B. | Constant volume |
| C. | Isothermal |
| D. | Free expansiton |
| E. | Throttling |
| Answer» C. Isothermal | |
| 372. |
If a process can be stopped at any stage and reversed so that the system and surroundings are exactly restored to their initial states, it is known as |
| A. | Isothermal process |
| B. | Thermodynamic process |
| C. | Ideal process |
| D. | Adiabatic process |
| E. | Reversible process |
| Answer» E. Reversible process | |
| 373. |
Which of the following does not change during an-ideal throttling process? |
| A. | Pressure, volume and temperature |
| B. | Enthalpy |
| C. | Pressure and volume |
| D. | Temperature and pressure |
| E. | Enthalpy and temperature |
| Answer» B. Enthalpy | |
| 374. |
The process in which no heat enters or leaves the system is called |
| A. | Isobaric |
| B. | Isothermal |
| C. | Isentropic |
| D. | Isochoric |
| E. | None of the above |
| Answer» C. Isentropic | |
| 375. |
Which is incorrect statement about the reversible process? |
| A. | A reversible process is ideal |
| B. | A reversible process must pass through a continuous series of equilibrium states |
| C. | A reversible process when undone, will leave no history of the events in the surroundings |
| D. | A reversible process must pass through the same states on the reversed path as were initially visited on the forward path |
| E. | None of the above |
| Answer» E. None of the above | |
| 376. |
For water which of the following will be reduced to zero at critical pressure? |
| A. | Specific volume |
| B. | Enthalpy |
| C. | Internal energy |
| D. | Latent heat of vaporisation |
| E. | None of the above |
| Answer» D. Latent heat of vaporisation | |
| 377. |
In case of centrifugal compressors, the phenomenon of air stream not able to follow the blade contour of an axial compressor is known as |
| A. | Stalling |
| B. | Feedback |
| C. | Regeneration |
| D. | Recirculation |
| E. | Surging |
| Answer» A. Stalling | |
| 378. |
If the rate of heat flow in aboves case remains constant, the ratio of temperature difference (?t1) (?t2) would be |
| A. | 16 ; 1 |
| B. | 1 ; 4 |
| C. | 8 ; 1 |
| D. | 1 ; 16 |
| E. | 1 ; 8 |
| Answer» A. 16 ; 1 | |
| 379. |
The ratio of heat flow QA/QB from two walls of same thickness having thermal conductivity kA = 2 kB, for the same temperature difference will be |
| A. | 1 |
| C. | 2 |
| D. | 0.5 |
| E. | None of the above |
| Answer» C. 2 | |
| 380. |
Adiabatic bulk modulus is Y times the isothermal bulk modulus |
| A. | Pulsejet |
| B. | for liquids only |
| C. | for real gases only |
| D. | for perfect gases only |
| E. | for all fluids |
| Answer» E. for all fluids | |
| 381. |
A fusible plug is utilised when |
| A. | Impurities in water are excessive |
| B. | Water level is too low |
| C. | Water level is too high |
| D. | Firing rate is high |
| E. | Steam generation rate is high |
| Answer» B. Water level is too low | |
| 382. |
A carnot cycle engine operating between temperature range of 50?C and 100?C will have the efficiency of nearly |
| A. | 50% |
| B. | 26.80% |
| C. | 13.40% |
| D. | Pulsejet |
| E. | 40% |
| Answer» C. 13.40% | |
| 383. |
Free piston engines find application in |
| A. | Compression air supply |
| B. | Mining installation |
| C. | Gas turbines |
| D. | supercharging reciprocating engines |
| E. | None of the above |
| Answer» C. Gas turbines | |
| 384. |
For a pure substance at its triple point, the number of degrees of freedom is |
| A. | 0 |
| B. | 1 |
| C. | 2 |
| D. | None of the above |
| E. | Pulsejet |
| Answer» A. 0 | |
| 385. |
A control volume refers to |
| A. | An isolated system |
| B. | A specified mass |
| C. | A fixed region in space |
| D. | A closed system |
| E. | A reversible process only |
| Answer» C. A fixed region in space | |
| 386. |
In an adiabatic change the system |
| A. | Heat taken from surroundings is exactly equal to heat rejected to surroundings |
| B. | Exchanges no heat with the surroundings |
| C. | Gives heat to the surrounding |
| D. | Partly takes heat and partly leaves to the surroundings |
| E. | Takes heat from the surroundings |
| Answer» B. Exchanges no heat with the surroundings | |
| 387. |
In case of axial flow compressors for minimum fluid driction and blade tip clearance losses, the blades of an axial flow compressor are disigned for |
| A. | 53% reaction |
| B. | 90% reaction |
| C. | 60% reaction |
| D. | Less than 50% reaction |
| E. | 75% reaction |
| Answer» A. 53% reaction | |
| 388. |
If the temperature of the source is increased, the efficiency of the Carnot engine |
| A. | Will be equal to the efficiency of a practical engine |
| B. | Increases |
| C. | Does not change |
| D. | Depends on their factors |
| E. | Decreases |
| Answer» B. Increases | |
| 389. |
In Porous plug experiment the change in temperature of a gas depends upon |
| A. | its molecular weight |
| B. | its specific heat |
| C. | pressure gradient on either side |
| D. | All of the above |
| E. | Pulsejet |
| Answer» C. pressure gradient on either side | |
| 390. |
"What two dissimilar metals are heated at one end cooled at the other c.m.f. is developed proportional to difference of temperatures at two ends". Which of the following name is associated with the above statement? |
| A. | Euler |
| B. | Peltier-Thomson |
| C. | Gay-Lussac |
| D. | Faraday |
| E. | Kelvin-planck |
| Answer» B. Peltier-Thomson | |
| 391. |
Which two cycles have one constant volume, one constant pressure and two adiabatic processes each? |
| A. | Brayton and Joules cycle |
| B. | Diesel and Dual cycles |
| C. | Otto and Carnot cycles |
| D. | Sterling and Diesel cycles |
| E. | Pulsejet |
| Answer» D. Sterling and Diesel cycles | |
| 392. |
If the door of a refrigerator in a room is left open, the temperature of the room will |
| A. | decrease |
| B. | Pulsejet |
| C. | remain unaltered |
| E. | increase |
| Answer» E. increase | |
| 393. |
For the same heat inpur and same compression ratio |
| A. | Otto cycle and Diesel cycle are equally efficient |
| B. | Otto cycle is less efficient than diesel cycle |
| C. | Efficiency depends mainly on working substance |
| D. | None of the above |
| E. | Rankine |
| Answer» D. None of the above | |
| 394. |
In case of six stage compression of air for minimum work conditions |
| A. | Pressure rise per stage will be equal |
| B. | Cylinder volumes will be identical |
| C. | Temperature rise in the cylinders will be the same |
| D. | Work done in successive stages will be in geometrical progression |
| E. | Piston diameters will be identical |
| Answer» D. Work done in successive stages will be in geometrical progression | |
| 395. |
The value of characteristic gas constant in kg metre per kg per deg C as |
| A. | 29.97 |
| B. | 1554 |
| C. | 848 |
| D. | 96 |
| E. | 53.3 |
| Answer» A. 29.97 | |
| 396. |
The processes or systems that do not involve heat are called |
| A. | Adiabatic processes |
| B. | Steady processes |
| C. | Equilibrium processes |
| D. | Thermal processes |
| E. | Isothermal processes |
| Answer» A. Adiabatic processes | |
| 397. |
The vapour pressure of water at 30?C in pascals is |
| A. | 0.44 |
| B. | 4315 |
| C. | 223 |
| D. | 431.5 |
| E. | 7.18 |
| Answer» B. 4315 | |
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