# PTS WAPDA Junior Engineer (Mechanical) Test Past Paper 2021

Pakistan Testing Service (PTS) conducted a test for the post of Junior Engineer (Mechanical) BPS-17 in Water and Power Development Authority (WAPDA). The test was conducted on 18th Jan 2021.

One of our students appeared in this test. We have gathered a few MCQs with their answers that were the part of this test. The test comprised of 100 MCQs. 90 MCQs were from Mechanical Engineering and 10 MCQs included English, Islamiyat, and General Knowledge.

You can view some MCQs from this test on our site our download the Sample Paper of Junior Engineer (Mechanical) in PDF.

1. The mechanism used in a petrol engine is
 A. Crank mechanism B. Slider mechanism C. Slider crank mechanism D. Natural line and circular mechanism E. None of the above
2. The rectilinear motion of a piston is converted into rotary motion by
 A. Piston rod B. Crank C. Piston pin D. Connecting rod E. Cross-head
3. The linear velocity of a point on a link relative to any other point on the link will be
 A. Along the line joining the two points B. Perpendicular to the line joining the two points C. Same as that of the end points of link D. Perpendicular to the lower end of the link E. None of the above
4. Dynamic of machines deals with
 A. The relative motion between the parts, neglecting the consideration of forces B. The forces acting on the parts of the machine C. The apparatus for applying mechanical power D. The number of inter-related parts, each having a definite motion E. None of the above
5. In simple harmonic motion the acceleration is proportional to
 A. Displacement B. Linear velocity C. Angular velocity D. Rate of change of angular velocity E. None of the above
6. The Biflar suspension method is used to determine
 A. Position of balancing weights B. Centripetal acceleration C. Natural frequency of vibration D. Moment of inertia E. None of the above
7. In the case of lower pairs
 A. There is surface contact between the two elements while in the motion B. There is line contact between the two elements while in the motion C. There is point contact between the two elements while is motion D. The contact is only at lower end of the two elements while in motion E. None of the above

8. In case of higher pairs
 A. There is contact only at higher point of the two elements while in motion B. There is only line or point contact between the two elements while in motion C. There is only line or point contact between the two elements while in motion D. There is no contact between the two elements E. None of the above
9. In an automobile the power is transmitted from gearbox to differential through
 A. Knuckle join B. Universal joint C. Oldham’s coupling D. Hooke’s joint E. Bevel gears
11. A piston and cylinder in a slider-crank mechanism form a
 A. Sliding pair B. Rolling pair C. Turning pair D. Cylindrical pair E. Sliding pair
12. A pantograph is a mechanism or a kinematic arrangement comprising
 A. A lower pair B. Two lower pairs C. Three lower pairs D. 10 links E. None of the above
13. Which one of the following is a higher pair?
 A. Thompson indicator mechanism B. Double McInnes Indicator mechanism C. Hart’s straight line mechanism D. Crossby indicator mechanism E. Tooth gearing mechanism
14. In a cam and follower mechanism, for the uniform velocity of the followers the displacement curve will have
 A. No slope B. Constant slope C. Slope in positive direction only D. Slope in both positive and negative direction E. None of the above
15. A point on a link connecting double slider crank chain, traces a
 A. Straight line path B. Circular path C. Parabolic path D. Hoperbolic path E. Elliptical path
16. If a particle of a link has a velocity when changes both in magnitude and direction at any instant, then
 A. It must have only unidirectional acceleration B. It must have two components of acceleration e.g. centripetal, and tangential C. It must have three components of acceleration e.g. centripetal centrifugal and tangential D. It must have three components of acceleration e.g. centripetal, centrifugal and gravitational E. It must have four components of acceleration e.g. centripetal, centrifugal gravitational and tangential
 A. One that reciprocates in the guides B. One that oscillates C. One in which the follower translates along an axis passing through the cam centre of rotation D. One in which the axis of the following movement is displaced from the cam centre E. None of the above
18. In the cam mechanism, a mushroom follower is
 A. One which moves in zig-zag path B. One which moves irregularly with uniform movement of cam C. One provided with a flat face with a perfect flat plane D. One identical to a knife edge follower with spherical end E. One with cylindrical roller held by a pin to the follower assembly
19. A pair is termed as a higher pair when relative motion between two elements of the pair is
 A. turning only B. sliding only C. rolling only D. partly sliding and partly turning
20. In case of Scotch Yoke Mechanism the Coriolis component is
 A. Involved B. Not involved C. Sometimes involved D. Involved if some other conditions are satisfied E. Involved but generally neglected
21. Coriolis component of acceleration will exist only if
 A. There are two coincidental points B. Two coincident points have relative angular velocity of sliding C. Two coincidental points have linear relative velocity of sliding accompanied by the rotation about fixed centres D. The two coincidental points must have same centre of rotation E. None of the above
22. The direction of Corioli’s component of acceleration is
 A. The direction of relative velocity vector for the two coincidental points rotated by 90? in the direction of the angular velocity of the rotation of the link B. The direction of relative velocity vector for the two coincidental points rotated by 180? in the direction of the angular velocity of the rotation of the link C. The direction of relative velocity vector for the two coincidental points in the direction directly opposite to that of angular velocity D. The direction at right angles to that of relative angular velocity vector E. None of the above
23. Coriolis component is not involved in
 A. Quick return mechanism B. Tangent cam acceleration C. Andreau variable stroke engine mechanism D. Line sliding in a swivelling pin E. Slider crank mechanism
24. The type of governor used in record players for adjusting the speed of turn table generally is
 A. Hartung governor B. Pickering governor C. Proell governor D. Porter governor E. Simple Watt’s governor
25. Idler pulley is used for
 A. Maintaining belt tension B. Changing direction of rotation C. For stopping motion frequently D. For running during idling periods only E. None of the above
26. By using large thread angles in a lifting machine
 A. The mechanical advantage will be high B. The load will be sustained in absence of effort C. The mechanical advantage will be low D. The load will be easily lifted E. While unloading, little effort will be required
27. Which is incorrect statement, if any
 A. The force of friction is independent of the velocity of sliding B. The force of friction is independent of the extent of the surfaces in contact C. The force of friction is directly proportional to the pressure between the surfaces in contact D. The laws of friction are true when the intensity of the pressure between the surfaces is small E. None of the above
28. The purpose of providing multiple collars on a flat collar pivot bearing is to
 A. Increase frictional resistance B. To establish self-sustaining bearing condition C. Distribute the frictional load because of limiting friction D. Distribute the axial load because of limiting bearing pressure on a collar E. None of the above
29 In case of flat belt drive the length of belt in case of
 A. Open belt depends on sum of the diameters of pulleys B. Open belts depends on difference of the diameters of pulleys C. Cross belts depends on the sum of the diameters of pulleys D. Cross belts depends on the difference of the diameters of pulleys E. None of the above
30. A nut and bolt form a
 A. Turning pair B. Rolling pair C. Spherical pair D. Sliding pair E. Helical pair
31. In order that a belt may not run off the pulley
 A. It should be properly tightened B. The centre line of the belt as it approaches the pulley must lie in a plane perpendicular to the axis of that pulley C. The belt should be provided with frictional material D. The belt should be provided with a guide E. None of the above
32. In case of belt drives, the effect of centrifugal tension is
 A. To reduce the driving power B. To increase the driving power C. Not appreciable on driving power D. Dependent on other factors E. None of the above
33. The function of a governor is
 A. To control the engine speed B. To maintain the speed of engine constant C. To maintain constant piston speed of engine D. To maintain the speed of an engine within prescribed limits of varying load conditions E. None of the above
34. Sensitiveness of a governor is
 A. The range of variation of engine speed B. The ratio of the maximum speed to minimum speed within the operating range C. The ratio of the difference between the maximum and mean speed to that of minimum to mean speed D. The ratio of the difference between the maximum and minimum equilibrium speed to the mean equilibrium speed E. None of the above
35. Isochronism in a governor is desirable when
 A. The engine operatres at low speeds B. The engine operates at high speeds C. The engine operates at variable speeds D. One speed is desired to be kept for all loads E. One speed is desired under one load
36. Which one of the following is a transmission type dynamometer?
 A. Prony brake B. Rope brake C. Hydraulic dynamometer D. Electric generator types E. None of the above

37. Which of the following preferred for supercharging of internal combustion engines?
 A. Roots blower B. Axial flow compressor C. Sliding vane type compressor D. Reciprocating compressor
38. An axial flow compressor is suitable for
 A. high volume flow rates with a small pressure rise B. high volume flow rates with high pressure rise C. low volume flow rates with low pressure rise D. low volume flow rates with high pressure rise
39. A regenerator can be used on
 A. open cycle gas turbines only B. closed cycle gas turbines only C. both open as well as closed cycle gas turbines
40. In which of the following heat exchanger, heat is extracted from air?
 A. Regenerator B. Reheater C. Intercooler D. All of the above
41. In which of the following plant inferior quality fuel can be used?
 A. Open cycle gas turbine with regeneration B. Open cycle gas turbine with intercooling C. Open cycle gas turbine with reheating and regeneration D. Closed cycle gas turbine
42. In a reheating gas turbine cycle, reheating is done
 A. by gases from turbine exhaust B. by gases from intercooler C. in separate combustion chamber D. any of the above
43. The ratio of actual velocity to the local velocity of sound is called
 A. Velicity ratio B. Velocity factor C. Speed ratio D. Mach number
44. In a nozzle under choked flow conditions pressure waves travel, in the divergent portion, at
 A. subsonic speed B. sonic speed C. supersonic speed D. subsonic to supersonic speed
45. The flow on two sides of a normal shock wave is
 A. subsonic B. sonic C. supersonic D. supersonic on one side and subsonic on the other side
46. A diffuser
 A. converts kinetic energy into thermal energy B. converts potential energy into kinetic energy C. converts pressure energy into kinetic energy D. converts thermal energy into kinetic energy
47. Brayton cycle cannot be used in reciprocating engines even for same compression ratio and work output because
 A. Otto cycle is more efficient B. Brayton cycle is less efficient C. Brayton cycle is for slow speed engines only D. Large volume of low pressure gas cannot be efficiently handled in reciprocating engines
48. Overall efficiency of a gas turbine is
 A. equal to Rankine cycle efficiency B. equal to Carnot cycle efficiency C. less than Diesel cycle efficiency D. more than Otto or Diesel c
49. All of the following are positive displacement compressors EXCEPT :
 A. Screw compressor B. Axial flow compressor C. Roots blower D. Vane blower
50. For efficient operation of axial flow compressors the blades are made
 A. straight B. slightly curved C. aerofoil section D. forward curved
51. Which of the following steam turbine has identical fixed and moving blades?
 A. Curtis turbine B. Rateau turbine C. Parson’s turbine D. none of the above
52. The continuity equation in compressible fluids is derived on the basis of
 A. conservation of momentum B. conservation of energy C. conservation of mass D. conservation of velocity head
53. As there is plenty of time for heat transfer across the walls, the flow in long pipes at low velocities attains
 A. isentropic conditions B. adiabatic conditions C. isothermal conditions D. polytropic conditions
54. In a hot wire anemometer the rate of heat loss from sensing element is a function of
 A. pressure B. mass rate of flow C. velocity of flow D. none of the above
55. The normal shock wave in compressible flow is analogous to
 A. surges in open channel B. vortex formation in centrifugal pump C. hydraulic bore in tidal rivers D. hydraulic jump in channel flow
56. Normal standard of compression for rotary compressor is
 A. adiabatic compression B. polytropic compression C. isentropic compression D. constant pressure compression
57. Though there are no cyclic variations even then rotary compressors need precise balancing because
 A. It is bulky in size B. cooling arrangement does not exist C. operating speeds are too high D. it is driven by an electric motor
58. The source of power for driving a turbocharger is
 A. kinetic energy of exhaust gases from the engine B. chemical energy of exhaust gases C. air motor D. electric motor
59. Which type of rotary compressor is used in oil fired furnaces?
 A. Sliding vane type blower B. Screw compressor C. Axial flow compressor D. Centrifugal blower
60. In rotory compressors, the ratio of isentropic work to Eulers work is known as
 A. slip factor B. work factor C. pressure coefficient D. degree of reaction
61. Stalling of the blades of axial flow compressor is
 A. an unsteady periodic and reversal of flow B. the fixed mass flow rate regardless of pressure ratio C. the reduction in lift force at higher angle of incidence D. none of the above
62. Surging is
 A. an unsteady, periodic and reversal of flow in the compressor B. the fixed mass flow rate regardless of pressure ratio C. the reduction in lift force at higher angles of incidence D. none of the above
63. Choking is
 A. Variation of mass flow rate in proportion to pressure ratio B. variation of mass flow rate in inverse proportion to pressure ratio C. fixed mass flow rate regardless of pressure ratio D. none of the above
64. Gas turbines are taken to
 A. the gasoline and diesel engines in its working medium B. the petrol and diesel engines in its internal combustion C. the steam turbine in its aspect of steady flow of the working medium D. All of the above
65. The advantage of closed cycle gas turbine over open cycle gas turbine is
 A. no contamination of working substance with combustion gases B. inferior quality fuel can be used C. low maintenance costs D. All of the above
66. When working substance is released through nozzles, the direction of reaction will be
 A. clockwise B. counter clockwise C. either of (A) and (B) above D. direction depends on other design features
67 In a velocity compounded steam turbine, as steam moves along moving and guide blades
 A. pressure is low and velocity gradually decreases B. pressure gradually increases and velocity is low C. both pressure and velocity gradually decrease D. Both pressure and velocity gradually increase.
68. Bleeding in steam turbine refers to
 A. leakage of steam through bearings B. leakage of steam through packings C. purposely withdrawn steam for process application D. purposely withdrawn for feed water heating
69. Which of the following loss in steam turbines is negligible?
 A. Residual velocity loss B. Leakage loss C. Mechanical friction loss D. Radiation loss
70. Which of the following rotary compressor has two shafts?
 A. Axial flow compressor B. Sliding vane compressor C. Centrifugal compressor D. Lobe type compressor
71. The following property is the most important for material used for gas turbine blades
 A. Fatigue B. Strength against bending C. Group D. Strength against direct force

72. Which of the following is the smallest and lighest for generating a given amount of power
 A. Steam power plant B. Petrol engine C. Diesel engine D. Solar plant E. Gas turbine plant
73. For gas turbine, compressors used are
 A. Reciprocating type B. Centrifugal type C. Axial flow type D. Lobe type E. Sliding vane type
74. Most serious energy loss in reaction steam turbine
 A. Steam leakage between diaphragm and shaft B. Leakage over blade ends through radia clearance passages C. Frictional resistance between steam and nozzle side D. Impact loss as steam enters moving blades E. Bearing friction
75. With the increase in pressure ratio, thermal efficiency of a simple gas turbine plant with fixed turbine inlet temperature
 A. increases B. decreases C. first increases and then decreases D. none of the above
76. With ideal regenerative heat exchanger, the thermal efficiency of gas turbine cycle is
 A. equal to work ratio B. is less than work ratio C. is more than work ratio D. none of the above
77. Greater the difference between jet velocity and aeroplane velocity
 A. greater the propulsive efficiency B. Lesser the propulsive efficiency C. unaffected is the propulsive efficiency D. None of the above
78. The accuracy depends upon
 A. Precision of instrument B. Precision of method C. Good planning D. All of the above E. None of the above
79. Natural error in measurement may be due to
 A. Humidity B. Temperature C. Wind D. Gravity E. Any of the above
80. The statement “The most probable value of an observed quantity available from a given set of observation is the one for which the sum of the square of errors is a minimum” is known as
 A. Law of square probability B. Pythogorus theorem C. Principle of least squares D. Law of errors E. Principle of square errors
81. The maximum allowable limit that a measurement may vary from the true value is called
 A. Permissible error B. Expected error C. Range of error D. Least error E. Safe error
82. Odometer is used to measure
 A. Threshold odours B. Composition of gases C. Suspended solids in a gas D. Distances E. Velocities and accelerations

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