Quiz: Mechanical Engineering 24 July 2020

Quiz: Mechanical Engineering
Exam: ISRO (TECHNICAL ASST.)
Topic: Miscellaneous

Each question carries 4 mark.
Negative marking: 1 mark
Time: 15 Minute

Q1. An isolated system is one in thermodynamics in which there is
(a) energy and mass transfer
(b) no energy and mass transfer
(c) energy transfer but no mass transfer
(d) no energy transfer but mass transfer

Q2. A heat pump for domestic heating operates between a cold system at 0°C and the hot
system at 6°C. What is the minimum electric power consumption if the heat rejected is 40000 kJ/hr?
(a) 2 kW
(b) 3 kW
(c) 4 kW
(d) 5 kW

Q3. Vertical component of pressure force on a submerged curved surface is
(a) equal to the force on a vertical projection of the curved surface
(b) equal to horizontal force component
(c) equal to the product of pressure at centroid and surface area
(d) equal to the gravity force of liquid vertically above the curved surface up to free surface

Q4. Which of the following is the effect of large clearance volume in reciprocating compressor?
(a) increased volume flow rate
(b) reduced volume flow rate
(c) lower suction pressure
(d) lower discharge pressure

Q5. Which of the following is a method to achieve maximum heat dissipation through a fin? (a) It should have maximum lateral surface at the root side of the fin
(b) it should have maximum lateral surface towards the tip side of the fin
(c) It should have maximum lateral surface near the centre of the fin
(d) It should have minimum lateral surface near the centre of the fin

Q6. Which of the following is used for the cooling of piston of an I.C. engine?
(a) Water
(b) Air
(c) Fuel oil
(d) Lubricating oil

Q7. Which of the following is the effect of changing center distance between gears in involute gear system?
(a) Pressure angle changes
(b) Velocity ratio changes
(c) Pitch circle remain unaffected
(d) Law of gearing does not satisfy

Q8. Which of the following type of bolt is preferred for service conditions involving jarring, vibration and pulsation of the working load?
(a) long bolt with increased elasticity
(b) short bolt with high rigidity
(c) bolt with castle nut
(d) bolt with a dished washer

Q9. Which of the following is also the second name of line imperfection?
(a) Miller defect
(b) Frenkel defect
(c) Schottky defect
(d) Edge dislocation

Q10. On which of the following place on a cutting tool, flank wear occurs?
(a) Relief face of the tool
(b) Rake face
(c) Cutting edge
(d) Nose of the tool

Solutions

S1. Ans (b)
Sol. There are three types of thermodynamic systems:
Open system: Both mass and energy transfer take place
Closed system: Only energy transfer takes place
Isolated system: No mass and energy transfer take place.

S2. Ans (a)
Sol. Given data
T2=0°C=273 K
T1=60°C
=(60+273)K=333K
Q1=80000 kJ/hr=40000/3600 kJ/s
= 11.11 kW
COP =T1/(T1-T2 )=333/(333-273)=5.55
Also, COP =Q1/W
∴5.55=11.11/W
or,W=11.11/5.55 = 2 kW

S3. Ans (d)
Sol. Vertical component of pressure force on the submerged curved surface is equal to the gravity force of liquid vertically above the curved surface up to the free surface.

S4. Ans (b)
Sol. The clearance volume is the space between piston top of inner surface of the cylinder head. The clearance volume reduces the capacity of the compressor and volume flow rate.

S5. Ans (a)
Sol. By having maximum lateral surface at the root side of the fin, we can get maximum heat dissipation through a fin.

S6. Ans (d)
Sol. Piston of diesel engine are usually cooled by lubricating oil. In addition, the lubricant on the cylinder walls must function as a seal to minimize the amount of gases of combustion that pass the piston rings and enter the crankcase.

S7. Ans (a)
Sol. The common tangent to the base circle changes when the distance between centre of two gears changes. So, the angle between the common tangent to base circle or action line with common tangent to pitch circle changes or pressure angel changes.

S8. Ans (c)
Sol. The castle nut consists of a hexagonal portion with a cylindrical upper part which is slotted in the line with the centre of each face. The split pin passes through two slots in the nut and a hole in the bolt, so that a positive lock is obtained unless the pin shears. It is extensively used in jobs subjected to sudden shocks and considerable vibration such as in automobile industry.

S9. Ans (d)
Sol. Edge dislocation is also known as line defect. Frankel and Schottky defect are both point defects.

S10. Ans (a)
Sol. Flank wear mainly occurs at the side relief face of the cutting tool due to friction between the workpiece surface and cutting tool face.

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