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MCQOPTIONS
This section includes 454 Mcqs, each offering curated multiple-choice questions to sharpen your Mechanical Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 401. |
A rotary compressor is driven by an |
| A. | Electric motor |
| B. | Engine |
| C. | Either (A) or (B) |
| D. | None of these |
| Answer» D. None of these | |
| 402. |
Maximum delivery pressure is a rotary air compressor is of the order of |
| A. | 6 kg/cm² |
| B. | 10 kg/cm² |
| C. | 16 kg/cm² |
| D. | 25 kg/cm² |
| Answer» C. 16 kg/cm¬¨‚⧠| |
| 403. |
In a single stage, single acting reciprocating air compressor without clearance volume, the work-done is maximum during |
| A. | Isothermal compression |
| B. | Isentropic compression |
| C. | Polytropic compression |
| D. | None of these |
| Answer» C. Polytropic compression | |
| 404. |
The area of actual indicator diagram on an air compressor as compared to area of ideal indicator diagram is |
| A. | Less |
| B. | More |
| C. | Same |
| D. | More/less depending on compressor capacity |
| Answer» C. Same | |
| 405. |
The thermal efficiency of a simple gas turbine for a given turbine inlet temperature with increase in pressure ratio |
| A. | Increases |
| B. | Decreases |
| C. | First increases and then decreases |
| D. | First decreases and then increases |
| Answer» B. Decreases | |
| 406. |
Inter-cooling in multistage compressors is done |
| A. | To cool the air during compression |
| B. | To cool the air at delivery |
| C. | To enable compression in two stages |
| D. | To minimize the work of compression |
| Answer» E. | |
| 407. |
In the axial flow gas turbine, the work ratio is the ratio of |
| A. | Compressor work and turbine work |
| B. | Output and input |
| C. | Actual total head temperature drop to the isentropic total head drop from total head inlet to static head outlet |
| D. | Actual compressor work and theoretical compressor work |
| Answer» D. Actual compressor work and theoretical compressor work | |
| 408. |
Isothermal compression efficiency can be attained by running the compressor |
| A. | At very high speed |
| B. | At very slow speed |
| C. | At average speed |
| D. | At zero speed |
| Answer» C. At average speed | |
| 409. |
Ratio of compression is the ratio of |
| A. | Gauge discharge pressure to the gauge intake pressure |
| B. | Absolute discharge pressure to the absolute intake pressure |
| C. | Pressures at discharge and suction corresponding to same temperature |
| D. | Stroke volume and clearance volume |
| Answer» C. Pressures at discharge and suction corresponding to same temperature | |
| 410. |
In a single stage, single acting reciprocating air compressor, without clearance, the work-done on the air during isentropic compression is ________ the heat required to raise the temperature of air from T‚ÇÅ to T‚ÇÇ at a constant pressure.$ |
| A. | Equal to |
| B. | Less than |
| C. | Greater than |
| D. | None of these |
| Answer» B. Less than | |
| 411. |
If p‚ÇÅ, is the pressure of air entering the L.P. cylinder and p‚ÇÇ is the pressure of air leaving the L.P. cylinder (or inter-cooler pressure), then the ratio of cylinder diameters for a single acting, two stage reciprocating air compressor with complete intercooling is given by (where D‚ÇÅ = Dia. of L.P. cylinder, and D‚ÇÇ = Dia. of H.P. cylinder)$ |
| A. | D‚ÇÅ/D‚ÇÇ = p‚ÇÅ p‚ÇÇ |
| B. | D‚ÇÅ/D‚ÇÇ = p‚ÇÅ/p‚ÇÇ |
| C. | D‚ÇÅ/D‚ÇÇ = p‚ÇÇ/p‚ÇÅ |
| D. | None of these |
| Answer» D. None of these | |
| 412. |
The efficiency of a jet engine is higher at |
| A. | Low speeds |
| B. | High speeds |
| C. | Low altitudes |
| D. | High altitudes |
| Answer» E. | |
| 413. |
Free air is the air at |
| A. | Atmospheric conditions at any specific location |
| B. | 20°C and 1 kg/cm² and relative humidity of 36% |
| C. | 0°C and standard atmospheric conditions |
| D. | 15°C and 1 kg/cm² |
| Answer» B. 20¬¨‚àûC and 1 kg/cm¬¨‚⧠and relative humidity of 36% | |
| 414. |
Propulsion efficiency of the following order is obtained in practice |
| A. | 34% |
| B. | 50% |
| C. | 60% |
| D. | 72% |
| Answer» D. 72% | |
| 415. |
The capacity of a compressor is 5 m/min refers to |
| A. | Standard air |
| B. | Free air |
| C. | Compressed air |
| D. | Compressed air at delivery pressure |
| Answer» C. Compressed air | |
| 416. |
Reheating in a gas turbine |
| A. | Increases the thermal efficiency |
| B. | Increases the compressor work |
| C. | Increases the turbine work |
| D. | Decreases the thermal efficiency |
| Answer» B. Increases the compressor work | |
| 417. |
A machine used to raise the pressure of air is called |
| A. | Gas turbine |
| B. | I.C engine |
| C. | Compressor |
| D. | Air motor |
| Answer» D. Air motor | |
| 418. |
The ideal efficiency of simple gas turbine cycle depends on |
| A. | Pressure ratio |
| B. | Maximum cycle temperature |
| C. | Minimum cycle temperature |
| D. | All of the above |
| Answer» B. Maximum cycle temperature | |
| 419. |
For perfect intercooling in a three stage compressor |
| A. | p‚ÇÇ/p‚ÇÅ = p‚ÇÉ/p‚ÇÇ = p‚ÇÑ/p‚ÇÉ |
| B. | p‚ÇÉ/p‚ÇÅ = p‚ÇÑ/p‚ÇÇ |
| C. | p‚ÇÅ p‚ÇÇ = p‚ÇÉ p‚ÇÑ |
| D. | p‚ÇÅ p‚ÇÉ = p‚ÇÇ p‚ÇÑ |
| Answer» B. p‚Äö√á√â/p‚Äö√á√Ö = p‚Äö√á√ë/p‚Äö√á√á | |
| 420. |
Only rocket engines can be propelled to space because |
| A. | They can generate very high thrust |
| B. | They have high propulsion efficiency |
| C. | These engines can work on several fuels |
| D. | They are not air breathing engines |
| Answer» E. | |
| 421. |
Rotary compressors are suitable for |
| A. | Large discharge at high pressure |
| B. | Low discharge at high pressure |
| C. | Large discharge at low pressure |
| D. | Low discharge at low pressure |
| Answer» D. Low discharge at low pressure | |
| 422. |
Which of the following fuels can be used in turbojet engines? |
| A. | Liquid hydrogen |
| B. | High speed diesel oil |
| C. | Kerosene |
| D. | Methyl alcohol |
| Answer» D. Methyl alcohol | |
| 423. |
The pressure of air at the beginning of the compression stroke is ________ the atmospheric pressure. |
| A. | Equal to |
| B. | Less than |
| C. | More than |
| D. | None of these |
| Answer» C. More than | |
| 424. |
In an axial flow compressor, the ratio of pressure in the rotor blades to the pressure rise in the compressor in one stage is known as |
| A. | Work factor |
| B. | Slip factor |
| C. | Degree of reaction |
| D. | Pressure coefficient |
| Answer» D. Pressure coefficient | |
| 425. |
The ratio of isentropic work to Euler work is known as |
| A. | Pressure coefficient |
| B. | Work coefficient |
| C. | Polytropic reaction |
| D. | Slip factor |
| Answer» B. Work coefficient | |
| 426. |
If the flow of air through the compressor is perpendicular to its axis, then it is a |
| A. | Reciprocating compressor |
| B. | Centrifugal compressor |
| C. | Axial flow compressor |
| D. | Turbo compressor |
| Answer» C. Axial flow compressor | |
| 427. |
In turbo fan engine, the jet velocity as compared to turbojet engine is |
| A. | Less |
| B. | More |
| C. | Same |
| D. | May be less or more depending upon speed |
| Answer» B. More | |
| 428. |
In a reciprocating air compressor, the compression work per kg of air |
| A. | Increases as clearance volume increases |
| B. | Decreases as clearance volume increases |
| C. | Is independent of clearance volume |
| D. | Increases as clearance volume decreases |
| Answer» D. Increases as clearance volume decreases | |
| 429. |
The following property is most important for material used for gas turbine blade |
| A. | Toughness |
| B. | Fatigue |
| C. | Creep |
| D. | Corrosion resistance |
| Answer» D. Corrosion resistance | |
| 430. |
The compression ratio for the compressor is always _________ unity. |
| A. | Equal to |
| B. | Less than |
| C. | More than |
| D. | None of these |
| Answer» D. None of these | |
| 431. |
As the turbine inlet temperature increases, the thermal efficiency of gas turbine for the optimum pressure ratio |
| A. | Increases |
| B. | Decreases |
| C. | Remain same |
| D. | First increases and then decreases |
| Answer» B. Decreases | |
| 432. |
In open cycle turbojet engines used in military aircraft, reheating the exhaust gas from the turbine by burning, more fuel is used to increase the |
| A. | Thrust and range of aircraft |
| B. | Efficiency of the engine |
| C. | Both (A) and (B) |
| D. | None of these |
| Answer» B. Efficiency of the engine | |
| 433. |
Pick up the false statement |
| A. | Gas turbine is a self starting unit |
| B. | Gas turbine does not require huge quantity of water like steam plant |
| C. | Exhaust losses in gas turbine are high due to large mass flow rate |
| D. | Overall efficiency of gas turbine plant is lower than that of a reciprocating engine |
| Answer» B. Gas turbine does not require huge quantity of water like steam plant | |
| 434. |
The ratio of the increase in pressure in rotor blades to total increase in pressure in the stage is called |
| A. | Pressure ratio |
| B. | Pressure coefficient |
| C. | Degree of reaction |
| D. | Slip factor |
| Answer» D. Slip factor | |
| 435. |
The mean effective pressure of the compressor is the |
| A. | Actual volume of the air delivered by the compressor when reduced to normal temperature and pressure conditions |
| B. | Volume of air delivered by the compressor |
| C. | Volume of air sucked by the compressor during its suction stroke |
| D. | None of the above |
| Answer» E. | |
| 436. |
The compressed air may be used |
| A. | In gas turbine plants |
| B. | For operating pneumatic drills |
| C. | In starting and supercharging of I.C. engines |
| D. | All of the above |
| Answer» E. | |
| 437. |
The minimum work required for a three stage reciprocating air compressor is ________ the work required for each stage. |
| A. | Equal to |
| B. | Double |
| C. | Three times |
| D. | Six times |
| Answer» D. Six times | |
| 438. |
In a compressor, free air delivered is the actual volume delivered at the stated pressure reduced to |
| A. | N.T.P. conditions |
| B. | Intake temperature and pressure conditions |
| C. | 0°C and 1 kg/cm² |
| D. | 20°C and 1 kg/cm² |
| Answer» C. 0¬¨‚àûC and 1 kg/cm¬¨‚⧠| |
| 439. |
The volumetric efficiency of compressor with increase in compression ratio will |
| A. | Increase |
| B. | Decrease |
| C. | Remain same |
| D. | May increase or decrease depending on clearance volume |
| Answer» C. Remain same | |
| 440. |
Rotary compressors are used for delivering |
| A. | Small quantities of air at high pressures |
| B. | Large quantities of air at high pressures |
| C. | Small quantities of air at low pressures |
| D. | Large quantities of air at low pressures |
| Answer» E. | |
| 441. |
Volumetric efficiency is |
| A. | The ratio of stroke volume to clearance volume |
| B. | The ratio of the air actually delivered to the amount of piston displacement |
| C. | Reciprocal of compression ratio |
| D. | Index of compressor performance |
| Answer» C. Reciprocal of compression ratio | |
| 442. |
The axial flow compressor is preferred in aircraft gas turbines because of |
| A. | Low frontal area |
| B. | Higher thrust |
| C. | High pressure rise |
| D. | None of these |
| Answer» B. Higher thrust | |
| 443. |
The absolute pressure of air at the outlet of a compressor is called |
| A. | Back pressure |
| B. | Critical pressure |
| C. | Discharge pressure |
| D. | None of these |
| Answer» D. None of these | |
| 444. |
Isothermal compression efficiency, even when running at high speed, can be approached by using |
| A. | Multistage compression |
| B. | Cold water spray |
| C. | Both (A) and (B) above |
| D. | Fully insulating the cylinder |
| Answer» D. Fully insulating the cylinder | |
| 445. |
The inlet pressure is always ________ the discharge pressure. |
| A. | Equal to |
| B. | Less than |
| C. | More than |
| D. | None of these |
| Answer» C. More than | |
| 446. |
The compressor capacity is defined as the |
| A. | Actual volume of the air delivered by the compressor when reduced to normal temperature and pressure conditions |
| B. | Volume of air delivered by the compressor |
| C. | Volume of air sucked by the compressor during its suction stroke |
| D. | None of the above |
| Answer» C. Volume of air sucked by the compressor during its suction stroke | |
| 447. |
The volumetric efficiency of a compressor falls roughly as follows for every 5°C increase in atmospheric temperature# |
| A. | 0.1% |
| B. | 0.5% |
| C. | 1% |
| D. | 5% |
| Answer» D. 5% | |
| 448. |
For maximum work, the reheating should be done to an intermediate pressure of (Where p‚ÇÅ = Maximum pressure, and p‚ÇÇ = Minimum pressure)# |
| A. | (p‚ÇÅ - p‚ÇÇ)/2 |
| B. | (p‚ÇÅ + p‚ÇÇ)/2 |
| C. | p‚ÇÅ/p‚ÇÇ |
| D. | p‚ÇÅ p‚ÇÇ |
| Answer» E. | |
| 449. |
In a high pressure compressor, the delivery pressure is |
| A. | 1 to 5 bar |
| B. | 5 to 8 bar |
| C. | 8 to 10 bar |
| D. | 10 to 15 bar |
| Answer» D. 10 to 15 bar | |
| 450. |
An ideal air compressor cycle without clearance on P-V diagram can be represented by following processes |
| A. | One adiabatic, two isobaric, and one constant volume |
| B. | Two adiabatic and two isobaric |
| C. | Two adiabatic, one isobaric and one constant volume |
| D. | One adiabatic, one isobaric and two constant volumes |
| Answer» B. Two adiabatic and two isobaric | |