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Multiple choice question for engineering

Set 1

1. Pankaj watches a jet in air with a long trail of exhaust gas at its rear. What type of engine do they run on?
a) Prop Jet
b) Back Pressure Gas Turbine
c) Jet Propulsion Gas Turbine
d) Steam turbine

View Answer

Answer: d [Reason:] Jet propulsion turbine provides high velocity and comfortable flight at very high altitudes.

2. Arrange the words to make a meaningful order: diffuser/exhaust cone/combustor/low pressure compressor/turbine/intercooler/high pressure compressor
a) low pressure compressor/ turbine/ intercooler/ diffuser/ combustor/ high pressure compressor/ exhaust cone
b) diffuser/ low pressure compressor/ intercooler/ high pressure compressor/ combustor/ turbine/ exhaust cone
c) diffuser/ high pressure compressor/ intercooler/ low pressure compressor/ combustor/ turbine/ exhaust cone
d) combustor/ low pressure compressor/ turbine/ intercooler/ exhaust cone/ high pressure compressor/ diffuser

View Answer

Answer: c [Reason:] Sequence of components in a Gas Turbine power plant.

3. Oil refineries seek significant application of gas turbine in which form:
a) They utilize waste hot gas from Houdry Cracking Process in order to drive a compressor
b) For peak load application
c) For standby application
d) For locomotive application

View Answer

Answer: a [Reason:] The waste gas from the process have enough energy to operate a gas turbine which is used to drive a compressor supplying compressed air for the houdry process.

4. Indian Railways has 2000 HP coal burning units(locomotive wagon) with their efficiency as 20%. Calorific value of coal is 30,000 KJ/Kg. Find mass of coal required per hp-sec?
a) 0.2486kg/s
b) 0.1110kg/s
c) 0.3568kg/s
d) 0.2254kg/s

View Answer

Answer: a [Reason:] Efficiency= work/heat supplied. Work is 2000 hp and heat supplied is mass flow rate * calorific value.

5. Engineers design a Gas Turbine Power Plant. Since the plant initial cost is too high, therefore engineers think to remove the regenerator from their original design. Then, immediate consequence of the same would be?
a) Compressor work will increase
b) Combustor will require more fuel
c) Turbine will produce more work output per unit of fuel
d) Requirement of Intercooler to compensate for its loss

View Answer

Answer: b [Reason:] Regenerators act as heat exchangers that heat the air before it enters the combustion chambers through exhaust gas emitting from exhaust cone.

6. Near a natural gas deposits, we require to set up a gas turbine plant. Geologist inform engineers that helium gas is found in abundance here. Hence, engineers seek to use helium as working medium for the gas power plant. This turbine is a,
a) Multi-shaft open cycle gas turbine
b) Single shaft open cycle gas turbine
c) Closed cycle gas turbine
d) Simple Open cycle Gas Turbine

View Answer

Answer: c [Reason:] Since the working fluid is other than air, therefore the plant is closed cycle gas turbine.

7. In order to generate energy in Sahara Desert where water is available in significantly low amount. Which system can we employ in such a place:
a) Steam Turbine
b) Gas Turbine
c) Steam Engine
d) Tidal Engine

View Answer

Answer: b [Reason:] As gas turbine require very little or no water at all for their functioning.

8. Fresh air at 14.7psi enters a compressor of a gas turbine and is compressed isentropically. The gas at the mouth of turbine is at 60 psi pressure and with specific volume as 50 m^3/kg. What would be the specific volume of fresh air?
a) 136.54m3/kg
b) 125.64m3/kg
c) 126.54m3/kg
d) 135.64m3/kg

View Answer

Answer: a [Reason:] PV^k=constant for isentropic process.

9. Assertion: Twin shaft arrangement of gas turbine must consist of two shafts whether in series or parallel. [Reason:] In multi shaft arrangement two or more turbine-compressor combinations are carried on independent shafts. Select the most appropriate options following.
a) Both assertion and reason are correct and reason precisely explains the assertion
b) Both assertion and reason are correct but reason doesn’t exactly explains the assertion
c) Assertion is correct whilst reason is incorrect
d) Assertion is incorrect whilst reason is correct

View Answer

Answer: d [Reason:] Single shaft arrangement must have all compressors and turbines to be coupled in a series arrangement.

10. The presence of high temperature conditions often limit the use of materials in the plant. Can you predict which of the options would be most suitable material for the gas turbine components?
a) Mn-Ni Alloy
b) Ti-Al-Sn-Zr Alloy
c) Stainless steel
d) Cast Iron

View Answer

Answer: b [Reason:] Titanium has best high temperature resistance and is almost unreactive even at elevated temperatures.

Set 2

1. How many burners are placed in can-annular combustors in gas turbines ?
a) 1
b) 3
c) 5
d) Not specific one or more

View Answer

Answer: d [Reason:] Multiple or single burners are evenly spaced in combustor.

2. Silo combustors are mounted Internal to gas turbine body.
a) True
b) False

View Answer

Answer: b [Reason:] Silo combustors are mounted external to the gas turbines.

3. Axial flow turbines are used in ________
a) industrial gas turbines
b) air crafts
c) hybrid vehicles
d) none of the mentioned

View Answer

Answer: a [Reason:] Axial flow gas turbines are mostly used for industrial purposes.

4. What completes a stage in Turbine expansion ?
a) One cycle passing through compressor
b) Row of moving blades followed by a row of stationary blades
c) Stationary blades row followed by Moving blades row
d) None of the mentioned

View Answer

Answer: c [Reason:] Turbine expansion takes place in stages. One stage comprises of a Row of stationary blades followed by a row of moving blades.

5. What does TRIT in a gas turbine stand for ?
a) Turbine Rotor Inlet Temperature
b) Total Raise at Inlet Temperature
c) Temperature Raise In Turbine
d) None of the mentioned

View Answer

Answer: a [Reason:] TRIT stands for Turbine Rotor Inlet Temperature and TIT stands for Turbine Inlet Temperature.

6. When at idle conditions Gas Turbine Engines use more fuel when compared to Reciprocating engines.
a) True
b) False

View Answer

Answer: a [Reason:] Though the conditions may be idle but to run the turbine compressor to work, compressor takes as much as the two thirds of the total power produced from combustion and remaining one third is used for power output. So during Idle conditions power output may not be required but compressor uses its 2/3 of energy, whereas reciprocating engines doesn’t require any compressors equipped separately and hence less fuel will be burnt during idle time when compared to Gas turbines.

7. In Gas Turbines Compressors raise the pressure of air by _______times.
a) 25
b) 15
c) 30
d) 10

View Answer

Answer: c [Reason:] Compressor work is to raise the pressure of the air at constant volume. In gas turbines it raises by a factor of 30.

8. In Gas Turbines, Turbine is used to convert _________
a) Kinetic energy to Rotational energy
b) Potential energy of the gases to Rotational energy
c) Heat energy of the gases to Rotational energy
d) None of the mentioned

View Answer

Answer: a [Reason:] Highly pressurized gas from compressor burns the fuel injected into combustor and those hot gases released move with high velocity towards turbine which rotates the turbine.

9. Hallow perforated piece of heavy metal inside the combustor is called as _________
a) Fuel injector
b) Frame holder
c) Burner
d) None of the mentioned

View Answer

Answer: b [Reason:] As gas with high pressure enters the combustor with high velocities, for continuous combustion, the combustor in such situations require the frame to be held and therefore frame holder is used.

10. Turbine and Output shaft rotate freely without any connection to the engine.
a) True
b) False

View Answer

Answer: a [Reason:] Turbine and output shaft are completely stand alone in gas turbine.

Set 3

1. The layer of a belt is generally called as
a) Ply
b) Layer
c) Segment
d) Sediment

View Answer

Answer: a [Reason:] Terminology.

2. Velocity ratio for chain drive is lesser than that for belts.
a) Yes
b) No
c) In some cases
d) Can’t be determined

View Answer

Answer: b [Reason:] Velocity ratio for chain drives is about 15:1 while for belts it is around 7:1.

3. Fabric rubber belts are not widely used as they can’t be operated at high speeds.
a) They can’t be used at velocities 50m/s
b) They can be used at high velocities
c) Limiting velocity is 20m/s
d) None of the listed

View Answer

Answer: b [Reason:] These belts can be operated at 300m/s.

4. Power transmitting capacity of V belts is more than that of flat belt.
a) Yes
b) No
c) Only for V angle > 15
d) None of the listed

View Answer

Answer: a [Reason:] Coefficient of friction is 2.92times of flat belts in V belts for identical materials.

5. The optimum velocity of the belt for maximum transmission is given by √P/6m.
a) Yes
b) No, by replacing 6 by 3
c) Replacing 6 by 9
d) None of the listed

View Answer

Answer: b [Reason:] It is given by √P/3m.

6. Creep is the slight absolute motion of the belt as it passes over the pulley.
a) Yes
b) No, it is a relative motion
c) None of the listed
d) It is absolute motion

View Answer

Answer: b [Reason:] It is a relative and not absolute motion.

7. In horizontal belt, the loose side is generally kept on the bottom.
a) True
b) False

View Answer

Answer: b [Reason:] Loose side is kept on the top so that arc of contact increases and hence efficiency of the drive increases.

8. Vertical drives are preferred over horizontal.
a) True
b) False

View Answer

Answer: b [Reason:] In vertical drive, gravitational force on the belt causes slip which reduces the efficiency.

9. The law of belting states that the centreline of the belt when it approaches a pulley must not lie in the midplane of the pulley.
a) True
b) False

View Answer

Answer: a [Reason:] The centreline must lie in the midplane.

10. It is possible to use the belting reverse direction without violating the law of belting.
a) True
b) False

View Answer

Answer: b [Reason:] Law of belting is violated if belt is used in reverse direction.

11. A shorter centre distance is always preferred in belt drives.
a) Yes due to stability
b) No due to stability
c) Yes due to instability
d) No due to instability

View Answer

Answer: a [Reason:] It is more stable and compact.

12. If velocity ratio is less than 3, then centre distance is given by D+.5d.
a) True
b) False

View Answer

Answer: b [Reason:] It is given by D+1.5d.

13. If velocity ratio is more than 3, then centre distance is given by 2D.
a) By 3D
b) By D
c) By 4D
d) By 5D

View Answer

Answer: b [Reason:] It is given by D.

14. Is it possible to reduce the centre distance as much as we want?
a) Yes power transmission increases
b) No
c) Can’t be cited
d) None of the listed

View Answer

Answer: b [Reason:] It depends on physical dimension and the minimum angle of wrap required to transfer the required power.

15. The diameter of the shorter pulley in leather belt drive is 265mm. It is rotating at 1440 rpm. Calculate the velocity of the belt.
a) 25m/s
b) 20m/s
c) 30m/s
d) None of the mentioned

View Answer

Answer: b [Reason:] v=πdn/60×1000.

Set 4

1. machine-design-questions-answers-hydrodynamics-bearing-q1
Answer the questions i-vii with respect to this figure

1. i. The bearing characteristic number shown in the graph is directly proportional to the unit bearing pressure.
a) True
b) False

View Answer

Answer: b [Reason:] BCN=µN/P.

2. ii. In the graph shown, which regions points the partial metal to metal contact.
a) BC
b) CD
c) Both BC and CD
d) Can’t be determined

View Answer

Answer: a Explanatiion: BC is the condition of thin film and hence surfaces are not completely separated.

3. iii. Hydrodynamic lubrication takes place in region?
a) BC
b) CD
c) Both BC and CD
d) None of the mentioned

View Answer

Answer: b [Reason:] In CD thick film of lubrication has developed.

4. iv. Coefficient of friction is minimum at
a) It is same at each point
b) B
c) C
d) D

View Answer

Answer: c [Reason:] It is minimum at the transition zone.

5. v. Bearing modulus is the bearing characteristic number at
a) B
b) C
c) D
d) None of the listed

View Answer

Answer: b [Reason:] BCN modulus is the the BCN number corresponding to the minimum coefficient of friction.

6. vi. If viscosity of the lubricant is very low than BCN will lie in the region
a) BC
b) Point C
c) CD
d) Can’t be determined

View Answer

Answer: a [Reason:] Due to low viscosity, lubricant will not separate the two surfaces resulting in partial contact.

7. vii. The fundamental equation for viscous flow is given by ∆pbhᵌ/6µl where symbols have their usual meanings.
a) 6 is to be replaced by 3
b) 6 is to be replaced by 12
c) 6 is to be replaced by 9
d) 6 is to be replaced by 15

View Answer

Answer: b [Reason:] It is givenby ∆pbhᵌ/12µl.

8. A single transverse weld is preferred over double transverse fillet weld.
a) True
b) False

View Answer

Answer: b [Reason:] A single transverse weld is not preferred because the edge of the plate which is not welded can warp out of shape.

9. Transverse fillet weld can be designed using the same equations as of parallel fillet weld.
a) True
b) False

View Answer

Answer: b [Reason:] Vice versa is true as strength of transverse fillet weld is greater than that of parallel fillet weld.

Set 5

1 .Find the torque required to raise the load of 15kN and mean diameter of triple threaded screw being 46mm. Also given pitch=8mm and coefficient of friction is 0.15.
a) 11831.06N-mm
b) 11813.06N-mm
c) 12811.06N-mm
d) None of the listed

View Answer

Answer: a [Reason:] tanἀ=l/πd or ἀ=9.429’ as l=3p. tan Ǿ=0.15 or Ǿ=8.531’. M=W x d x tan (Ǿ+ἀ)/2.

2. What is the collar friction torque if outer and inner diameters are 100mm and 65mm respectively. Coefficient of friction is 0.15 and the load acting is of 15kN. Consider uniform wear theory.
a) 89886.6N-mm
b) 38796.5N-mm
c) 92812.5N-mm
d) 87645.5N-mm

View Answer

Answer: c [Reason:] M=0.15 x W(D+d)/4.

3. For a double threaded screw, what will be the tangent of helix angle if nominal diameter and pitch are 100mm and 12mm respectively?
a) 0.045
b) 0.081
c) 0.094
d) 0.023

View Answer

Answer: b [Reason:] tan ἀ= l/πd where l=2p, d=D-0.5p.

4. If for a trapezoidal thread, angle of thread is 15’ then what will be the replacement of the coefficient of friction which is 0.15.
a) 0.1553
b) 0.1335
c) 0.1667
d) 0.1776

View Answer

Answer: a [Reason:] f=0.15 x sec 15’.

5. What will be efficiency of the screw in case of raising the load when coefficient of friction is 0.1553 and tangent of helix angle is 0.0813?
a) 34%
b) 45%
c) 54%
d) 43%

View Answer

Answer: a [Reason:] Efficiency= tanἀ(1-0.1553 x tan ἀ)/(0.1553+tanἀ).

6. A machine vice whose length of the handle is 150mm and the coefficient of friction for thread and collar are 0.15 and 0.17 respectively has a force applied at handle of 125N. Also the outer and inner diameters of collar are 55mm and 45mm respectively. Find the screw torque in terms of clamping force W if nominal diameter=22mm and pitch=5mm.
a) 3.567W N-mm
b) 2.286W N-mm
c) 3.564W N-mm
d) None of the mentioned

View Answer

Answer: b [Reason:] M₁=Wd x tan(Ǿ+ἀ)/2 or M₁=W x (22-0.5×2.5)x tan(4.66’+8.531’)/2 as tan(ἀ)=l/πd and tanǾ=0.15.

7. A machine vice whose length of the handle is 150mm and the coefficient of friction for thread and collar are 0.15 and 0.17 respectively has a force applied at handle of 125N. Also the outer and inner diameters of collar are 55mm and 45mm respectively. Find the collar torque in terms of clamping force W assuming uniform wear theory if nominal diameter=22mm and pitch=5mm.
a) 4.5W
b) 5.4W
c) 4.25W
d) 3.37W

View Answer

Answer: c [Reason:] M₂=0.17 x W x (55+45)/4 or M₂=4.25W N-mm.

8. A machine vice whose length of the handle is 150mm and the coefficient of friction for thread and collar are 0.15 and 0.17 respectively has a force applied at handle of 125N. Also the outer and inner diameters of collar are 55mm and 45mm respectively. Find the clamping force W if nominal diameter=22mm and pitch=5mm.
a) 4539.45N
b) 2868.73N
c) 3657.56N
d) 2134.34N

View Answer

Answer: b [Reason:] Net torque=M₁+M₂ or 125 x 150=2.286W + 4.25W or W=2868.73N.

9. A machine vice whose length of the handle is 150mm and the coefficient of friction for thread and collar are 0.15 and 0.17 respectively has a force applied at handle of 125N. Also the outer and inner diameters of collar are 55mm and 45mm respectively. Find the overall efficiency if nominal diameter=22mm and pitch=5mm.
a) 18.12%
b) 12.18%
c) 21.23%
d) 23.21%

View Answer

Answer: b [Reason:] Efficiency= W l/2π(M₁+M₂) where M₁=2.286W [M₁=Wd x tan (Ǿ+ἀ)/2 or M₁=W x (22-0.5×2.5) x tan (4.66’+8.531’)/2 as tan(ἀ)=l/πd and tan Ǿ=0.15]. M₂=4.25W [M₂=0.17 x W x (55+45)/4 or M₂=4.25W N-mm], l=5mm, W=2868.73N [Net torque=M₁+M₂ or 125 x 150=2.286W + 4.25W or W=2868.73N].

10. Find the bending stress to which a screw of nominal diameter 22mm is subjected when the clamp exerts a force of 5kN acts on it. The screw is double threaded and pitch of screw is 5mm.Given: Coefficient of friction is 0.15.It is assumed operator exerts a force of 250N at the handle of length 275mm.
a) 123.45N/mm²
b) 132.54N/mm²
c) 142.54N/mm²
d) 124.45N/mm²

View Answer

Answer: c [Reason:] Bending stress=32M/πdᵌ where M=250 x 275N-mm,d=22-2 x 0.5 x 5mm.

11. Find the torsional shear stress to which a screw of nominal diameter 22mm is subjected when the clamp exerts a force of 5kN on it. The screw is double threaded and pitch of screw is 5mm.Given: Coefficient of friction is 0.15.
a) 25.45N/mm²
b) 21.29N/mm²
c) 31.21N/mm²
d) 35.65N/mm²

View Answer

Answer: b [Reason:] =16M/πd₂ᵌ where M=Wd₁ tan (Ǿ+ἀ)/2 where d₁=22-0.5 x 5,W=5000N, tanἀ=2 x 5/[πx19.5] and d₂=19.5-0.5 x 5.

12. If bending stress in a screw is of magnitude 95N/mm² and torsional shear stress of magnitude 15N/mm², then what is the principal shear stress?
a) 48.7N/mm²
b) 54.3 N/mm²
c) 51.4 N/mm²
d) 49.8 N/mm²

View Answer

Answer: d [Reason:] τ(max)=√(95/2)²+15².

13. The nominal diameter of the screw is 22mm and the allowable bearing pressure for the nut is 15N//mm². Find the length of the nut if pitch of the screw is
a) 15mm
b) 20mm
c) 25mm
d) 30mm

View Answer

Answer: a [Reason:] z=4W/π S(d₁²-d₂²) where S=15N/mm²,d₁=22mm and d₂=17mm. Hencez=2.2 or z=3. Length of nut=zp or l=3 x 5= 15mm.

14. A but joint can be defined as a joint between two components lying approximately in a different plane.
a) True
b) False

View Answer

Answer: b [Reason:] Butt joint is defined a joint between two plates lying in the same plane.

15. A fillet weld is an approximately triangular cross section joining two surfaces lying parallels to each other.
a) True
b) False

View Answer

Answer: b [Reason:] Two surfaces lie perpendicular to each other.