ASSAM JLEE 2020: Mechanical Engineering (Section -IV) Answer Key

 

JLEE 2020

MECHANICAL ENGINEERING (SECTION - IV)

Answer Key

1. Which one of the following instruments is used to check the concentricity of the outside diameter?

        a) Vernier Caliper                       

        b) Outside micrometer  

        c) Dial test indicator 

        d) Dial caliper

2. Limits of 50 mm hole is ES = +0.025 and EI = +0.002. The maximum and minimum hole sizes will be:

        a) 50.02 mm; 49.998 mm                                    

        b) 50.025 mm; 50.002 mm

        c) 49.998 mm; 50.002 mm                                   

        d) 49.990 mm; 49.975 mm

3. A Carnot refrigerator rejects 2500 kJ of heat at 390 K while using 750 kJ of work. The lowest operating

    temperature of the cycle is:

        a) 300^oC                         

        b) 270^oC                      

        c) 27^oC                        

        d) 327^oC

4. Throttling operation occurs in:

        a) evaporator             

        b) expansion valve       

        c) condenser                

        d) receiver bank

5. At critical point the latent heat of vaporization is:

        a) zero                            

        b) more than one          

        c) less than one            

        d) none

6. Slag inclusion in casting is a:

        a) surface defect              

        b) crack                                   

        c) notch                          

        d) internal defect

7. Which of the following chemical compound, is the most common flux added to the charge in a cupola furnace?

        a) Coke                          

        b) Methane                  

        c) Carbon dioxide        

        d) Limestone

8. The process which employed for the production of seamless tubes, is known as:

        a) Extrusion                    

        b) Forging                    

        c) Casting                    

        d) Piercing

9. Carburising flame is a flame which is obtained by supplying:

        a) more volume of acetylene and less volume of oxygen

        b) less volume of acetylene and more volume of oxygen

        c) equal volume of acetylene and oxygen

        d) none of the above

10. Flux is not used for welding:

        a) cast iron                      

        b) Brass                 

        c) bronze                     

        d) carbon steel

11. The relationship between tool life (T) and cutting speed (V) is expressed as:

        a) VⁿT=Constant  

        b) VT^-1 = Constant

        c) TⁿV = Constant

        d) TV^-1 = Constant

12. A mild steel rod 300 mm long, 25 mm diameter is to be turned to reduce its diameter to 24 mm in one cut. If the rod is rotating at 510 rpm, the cutting speed would be equal to:

        a) 20 m/min                    

        b) 40 m/min                 

        c) 60 m/min                 

        d) 80 m/min

13. Change in enthalpy of a system is the heat supplied at:

        a) constant volume          

        b) constant pressure     

        c) constant temperature

        d) constant entropy

14. The volume of air delivered by the compressor is called:

        a) Compressor capacity   

        b) Free air delivery       

        c) Swept volume          

        d) Discharge pressure

15. The ignitation quality of fuels for SI engines is determined by:

        a) Cetane number rating  

        b) Octane number        

        c) Calorific value         

        d) Volatility

16. De-Lavel turbine is a:

        a) reaction turbine                                                           

        b) pressure compound turbine

        c) velocity compound turbine                               

        d) single wheel impulse turbine

17. Reheat factor (R.F.) is defined as:

        a) ratio of cumulative enthalpy drop to isentropic enthalpy drop

        b) product of cumulative enthalpy drop and isentropic enthalpy drop

        c) ratio of isentropic enthalpy drop to cumulative enthalpy drop

        d) none of the above

18. Shaft with collars at both ends fitted into a circular hole forms a:

        a) Turning pair                

        b) Rolling pair             

        c) Sliding pair              

        d) Spherical pair

19. Whitworth quick return mechanism is an inversion of:

        a) double slider crank chain                                 

        b) single slider crank chain 

        c) four bar chain                                                  

        d) crossed slider crank chain

20. A mechanism is having  links, then the number of instantaneous centres would be equal to:

        a) n                                 

        b) n (n-1)/2                      

        c) n/2                              

        d) none

21. Sublimation region is the region where:

        a) Solid and vapour phases are in equilibrium

        b) Solid and liquid phases are in equilibrium

        c) Solid, liquid and vapour phases is equilibrium

        d) none

22. The missing quantity is defined as:

        a) The difference in the volume at any point between the saturation curve and actual expansion curve

        b) The product of volume given by saturation curve and actual expansion curve

        c) The difference in volume given by the saturation curve and clearance volume

        d) none

23. The figure shown below is actual indicator diagram of a steam engine. The point C is called:

        a) Cut-off point                                       

        b) Release point                       

        c) Admission point                                  

        d) The point at which exhaust port closes

24. For which process, a steel is heated to the maximum temperature?

        a) Full annealing             

        b) Process annealing    

        c) Normalizing             

        d) Hardening

25. Spheroidizing process is carried out at:

        a) 480^oC                         

        b) 680^oC                      

        c) 550^oC                      

        d) none

26. By which process maximum hardness is obtained for a steel part?

        a) Carburizing

        b) Nitriding

        c) Cyaniding

        d) None of the above

27. A pattern carries which allowance for internal and external surface?

        a) Shrinkage allowance

        b) Machining allowance

        c) Distortion allowance

        d) Draft allowance

28. Shell moulding requires:

        a)Wooden patterns

        b) Sand patterns

        c) Metal patterns

        d) Plastic patterns

29. In transverse grinding:

        a) The work is reciprocated as the wheel feeds to produce cylinders longer than the width of wheel face

        b) The work rotates in fixed position as the wheel feeds to produce cylinders equal to or shorter than the width of wheel face

        c) The work is reciprocated as the wheel feeds to produce cylinders shorter than the width of wheel face

        d) The work rotates in a fixed position as the wheel feeds to produce cylinders longer than the width of wheel face

30. The lead screw of a lathe has ___________ threads.

        a) Single start

        b) Double start

        c) Multi start

        d) No threads

31. Crater wear is mainly due to the phenomenon known as:

        a) Adhesion of metals

        b) Oxidation of metals

        c) Diffusion of metals

        d) All of the above

32. A lathe is used to perform which one of the following operations?

        a) Breaching

        b) Turning

        c) Milling

        d) Lapping

33. When center of gravity of the balance weights is either directly below the wheel center or directly above the wheel center then

        a) Unbalanced horizontal force is maximum

        b) Unbalanced vertical force is maximum

        c) Unbalanced vertical force is minimum

        d) None of the above

34. During transverse vibration, shaft is subjected to which type of stresses?

        a) Tensile stresses

        b) Torsional shear stress

        c) Bending stresses

        d) All of the above

35. For a rope brake dynamometer, the flywheel is cooled with soapy water because:

        a) Energy is absorbed by the dynamometer

        b) Energy is used to do work

        c) Energy is provided by the motor    

        d) Energy supplied is more

36. What type of job motion is there in drilling machine?

        a) Rotary

        b) Translating

        c) Fixed

        d) None of the above

37. In how many groups cutting tools can be divided?

        a) 2

        b) 3

        c) 4

        d) 6

38. While current is shut down in the welding circuit, what kind of voltage  exists between the output terminals of the welding machine?

        a) GTAW

        b) Open air cut voltage

        c) Kerf

        d) Gougin

39. In which type of welding a gas shield, a consumable electrode is used and the can be done in all positions.

        a) ARC Welding

        b) TIG Welding

        c) Submerged ARC Welding

        d) MIG Welding

40. The process of coating iron or steel sheet with a thin coat of zinc to prevent iron from rusting is called

        a) Tinning

        b) Galvanisation

        c) Metal cladding

        d) Electroplating

41. The process of enlarging the end of an existing hole to accommodate the head of socket screw is called:

        a) Spot facing

        b) Boring

        c) Counter boring

        d) Counter sinking

42. In a shaper, rotary motion is converted into reciprocating motion by means of:

        a) Worm and worm wheel

        b) Rack and pinion

        c) Rocker arm end bull gear

        d) Shaft and pulley

43. In electron beam machining workpiece is held in:

        a) Vaccum chamber

        b) Dielectric medium

        c) Electrolyte

        d) None of these

44. In Plasma arc welding the electrode is made of:

        a) Tungsten

        b) Copper

        c) Brass

        d) Steel

45. The beginning or end of a task is called:

        a) An event

        b) An activity

        c) A part

        d) None of these

46. Founder of micromotion study is:

        a) Taylor

        b) Fayol

        c) Gilberth

        d) Mundel

47. When does a vapour become superheated?

        a) When the temperature of vapour is less than the saturation temperature at given pressure

        b) When the temperature of vapour is more than the saturation temperature at given pressure

        c) When the temperature of vapour is equal to the saturation temperature at given pressure

        d) None of the mentioned

48. The rate of heat transfer through hollow cylinder of radii r₁ and r₂ depends

        a) Difference of radii ( r₂ – r₁)

        b) Ratio of radii (r₂ / r₁)

        c) Product of radii (r₂ x r₁)

        d) Sum of radii (r₂ + r₁)

49. An oil cooler in a high performance engine has an outside surface are 0.1 m² and a surface temperature of 60 degree Celsius. At any intermediate time air moves over the surface of the cooler at a temperature of 30 degree Celsius and gives rise to a surface coefficient equal to 100 W/m² K. Find out the heat transfer rate?

        a) 300 W

        b) 3000 W

        c) 150 W

        d) None

50. Steel used for the plates of stone jaw crushers

        a) High Carbon  Steel

        b) Martensitic stainless steel

        c) Hadfield steel

        d) Triple alloy Steel

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