Quiz: Mechanical Engineering 24 April 2020

Quiz: Mechanical Engineering
Exam: NLC-GET
Topic: Miscellaneous

Each question carries 1 mark
Negative marking: 1/4 mark
Time: 10 Minutes
Q1. If the discharge of a centrifugal pump is throttled then its suction lift

(a)Decreases
(b) First increases and then decreases
(c) Remains unchanged
(d) Increases

Q2. If two objects are weighed in water and both of them lose the same weight, then the two objects must have identical

(a) Specific gravities
(b) Weights in air
(c) Densities
(d) Volumes

Q3. Which of the following regions of the electromagnetic spectrum would be used to determine the structure of crystalline solids?

(a) Microwave
(b) Infrared
(c) X-ray
(d) Visible

Q4. Precipitation hardening is applicable for

(a) Pure aluminium
(b) Low carbon steel
(c) Non- metal
(d) Aluminium- Copper alloy

Q5. Dislocations in material are

(a) Point defect
(b) Surface defect
(c) Planer defect
(d) Line defect

Q6. In the arc welding, penetration is minimum for

(a) DCSP
(b) DCRP
(c) AC
(d) DCEN

Q7. Two beams of equal cross-sectional area are subjected to equal bending moment. If one beam has square section and the other has circular section then.

(a) Both the beam will be equally strong
(b) Square section beam will be stronger
(c) Circular section beam will be stronger
(d) Depends on loading condition

Q8. To ensure self-locking in screw jack, it is essential that helix angle is

(a) Larger than friction angle
(b) None of these
(c) Equal to friction angle
(d) Smaller than friction angle

Q9. For a given heat flow and for the same thickness, the temperature drop across the material will be maximum for

(a) copper
(b) steel
(c) glass -wool
(d) refractory brick

Q10. A positive value of joule- Thompson coefficient of a fluid means

(a) Temperature drops during throttling
(b) Temperature remains constant during throttling
(c) Temperature rises during throttling
(d) None of these

SOLUTIONS

S1. Ans (d)
Sol. Due to decrease in flowrate velocity head loss as well as frictional loss decreases, by applying the Bernoulli’s equation, pump static suction pressure will increase.
As a result of this, NPSH will increases.

S2. Ans (d)
Sol. Buoyancy depends upon water volume displaced by body.
If volumes will be the same then lose in the weight of the body will also be the same.

S3. Ans (c)
Sol. X-ray diffraction method is used for the study of the material internal structure.

S4. Ans (d)
Sol. Precipitation hardening, also called age or particle hardening, is a heat treatment process that helps make metals stronger. The process does this by producing uniformly dispersed particles within a metal’s grain structure that help hinder motion and thereby strengthen it.

S5. Ans (d)
Sol. A dislocation is a linear crystallographic defect or irregularity within a crystal structure which contains an abrupt change in the arrangement of atoms.

S6. Ans (b)
Sol. In DC reverse polarity, electrons are transferred from plate to the electrode, so more heat (2/3 of total heat) generation takes place at electrode.

S7. Ans (c)
Sol. From same cross section area circular section beam has more section modulus than that of square section.

S8. Ans (d)
Sol. Helix angle should be smaller than friction angle to provide self-locking in screw jack.

S9. Ans(a)
Sol. Copper having the highest thermal conductivity along all the given options. So, it will give highest temp drop for same thickness.

S10. Ans(a)
Sol. Pressure is always decreasing in throttling process for positive Joule-Thompson coefficient temperature will drop.

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