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NPCIL Previous Paper - Mechanical Engineering
1. A streamline and an equipotential line in a flow field
(A) are parallel to each other
(B) are perpendicular to each other
(C) intersect at an acute angle
(D) are identical
2. If a mass of moist air in an airtight vessel is heated to a higher temperature, then
(A) specific humidity of the air increases
(B) specific humidity of the air decreases
(C) relative humidity of the air increases
(D) relative humidity of the air decreases
3. In a condenser of a power plant, the steam condenses at a temperature of 60 °C. The cooling water enters at 30 °C and leaves at 45 T. The logarithmic mean temperature difference (LMTD) of the condenser is
(A) 16.2 °C
(B) 21.6 °C
(C) 30 °C
(D) 37.5 °C
4. The maximum possible draft in cold rolling of sheet increases with the
(A) increase in coefficient of friction
(B) decrease in coefficient of friction
(C) decrease in roll radius
(D) increase in roll velocity
5. The operation in which oil is permeated into the pores of a powder metallurgy product is known as
(A) mixing
(B) sintering
(C) impregnation
(D) infiltration
6. Heat and work are
(A) intensive properties
(B) extensive properties
(C) point functions
(D) path functions
7. A column has a rectangular cross-section of 10 mmx 20 mm and a length of 1 m. The slenderness ratio of the column is close to
(A) 200
(B) 346
(C) 477
(D) 1000
8. Eigen values of a real symmetric matrix are always
(A) positive
(B) negative
(C) real
(D) complex
9. A pipe of 25 nun outer diameter carries steam. The heat transfer coefficient between the cylinder and surroundings is 5 W/m2K. It is proposed to reduce the heat loss from the pipe by adding insulation having a thermal conductivity of 0.05 W/mK. Which one of the following statements is TRUE?
(A) The outer radius of the pipe is equal to the critical radius.
(B) The outer radius of the pipe is less than the critical radius.
(C) Adding the insulation will reduce the heat loss.
(D) Adding the insulation will increase the heat loss.
10. The contents of a well-insulated tank are heated by a resistor of 23 Q in which 10 A current is f lowing. Consider the tank along with its contents as a thermodynamic system. The work done by the system and the heat transfer to the system are positive. The rates of heat (Q),work (W) and change in internal energy (AU) during the process in kW are
(A) Q = 0, W = -2.3, AU = +2.3
(B) Q = +2.3, W = 0, AU = +2.3
(C) Q = -2.3, W = 0, AU = -2.3
(D) Q = 0, W = +2.3, AU = -2.3
11. The product of two complex numbers 1 + i and 2 - 5i is
(A) 7 - 3i
(B) 3 - 4i
(C) - 3 - 4i
(D) 7+3i
12. Cars arrive at a service station according to Poisson's distribution with a mean rate of 5 per hour.The service time per car is exponential with a mean of 10 minutes. At steady state, the average waiting time in the queue is
(A) 10 minutes
(B) 20 minutes
(C) 25 minutes
(D) 50 minutes
14. The word kanban is most appropriately associated with
(A) economic order quantity
(B) just-in-time production
(C) capacity planning
(D) product design
15. The coefficient of restitution of a perfectly plastic impatt is
(A) 0
(B) 1
(C) 2
(D) 00
16. A thin cylinder of inner radius 500 mm and thickness 10 mm is subjected to an internal pressure of 5 MPa. The average circumferential (hoop) stress in MPa is
(A) 100
(B) 250
(C) 500
(D) 1000
17. Which one among the following welding processes uses non-consumable electrode?
(A) Gas metal arc. welding
(B) Submerged arc welding
(C) Gas tungsten are welding
(D) Flux coated arc welding
18. The crystal structure of austenite is
(A) body centered cubic
(B) face centered cubic
(C) hexagonal closed packed
(D) body centered tetragonal
19. The values of enthalpy of steam at the inlet and outlet of a steam turbine in a Rankine cycle are 2800 kJ/kg and 1800 kJ/kg respectively. Neglecting pump work, the specific steam consumption in kg/kW-hour is
(A) 3.60
(B) 0.36
(C) 0.06
(D) 0.01
20. Two identical ball bearings P and Q are operating at loads 30 kN and 45 kN respectively. The ratio of the life of bearing P to the life of bearing Q is
(A) 81/16
(B) 27/8
(C) 9/4
(D) 3/2
21. The shear strength of a sheet metal is 300 MPa. The blanking force required to produce a blank of 100 mm diameter from a 1.5 mm thick sheet is close to
(A) 45 kN
(B) 70 kN
(C) 141 kN
(D) 3500 kN
22. A pump handling a liquid raises its pressure from 1 bar to 30 bar. Take the density of the liquid as 990 kg/m3. The isentropic specific work done by the pump in kJ/kg is
(A) 0.10
(B) 0.30
(C) 2.50
(D) 2.93
23. A spherical steel ball of 12 mm diameter is initially at 1000 K. It is slowly cooled in a surrounding of 300 K. The heat transfer coefficient between the steel ball and the surrounding is 5 W/m2K. The thermal conductivity of steel is 20 W/mK. The temperature difference between the centre and the surface of the steel ball is
(A) large because conduction resistance is far higher than the convective resistance.
(B) large because conduction resistance is far less than the convective resistance.
(C) small because conduction resistance is far higher than the convective resistance.
(D) small because conduction resistance is far less than the convective resistance.
24. An ideal Brayton cycle, operating between the pressure limits of 1 bar and 6 bar, has minimum and maximum temperatures of 300 K and 1500 K. The ratio of specific heats of the working fluid is 1.4. The approximate final temperatures in Kelvin at the end of the compression and expansion processes are respectively
(A) 500 and 900
(B) 900 and 500
(C) 500 and 500
(D) 900 and 900
25. A single-point cutting tool with 12° rake angle is used to machine a steel work-piece. The depth of cut, i.e. uncut thickness is 0.81 nun. The chip thickness under orthogonal machining condition is 1.8 mm. The shear angle is approximately
(A) 22°
(B) 26°
(C) 56°
(D) 76°
