Insulation of liquid surface can be achieved by __________ on top of its surface.
Floating hollow polypropylene spheres
Spraying alumina powder
Putting cement
None of these
Correct Answer :
A. Floating hollow polypropylene spheres
Related Questions
In electrical resistance welding, distortion results from the use of improper
Clamping methods
Electrodes
Current
Filler material
Which of the following hardness tests does not measure the indentation hardness of metals and alloys?
Vickers hardness test
Shore scleroscope test
Brinell hardness test
Rockwell hardness test
Pick out the correct statement about the condensation.
Filmwise condensation gives a lower heat transfer rate than the dropwise condensation
Suitable coating or vapour additive is used to promote film wise condensation
If a condensing liquid does not wet the surface dropwise, even then condensation will take place on it
Reynolds number of condensing liquid is based on its mass flow rate
Two solutions A1 & A2 have pH value of 2 & 6 respectively. It implies that the solution
A1 is more alkaline than solution A2
A1 is highly acidic
A2 is very slightly acidic
Both (B) & (C)
Half life of a radioactive isotope corresponds to the time required for half of the __________ to decay.
Atoms
Neutrons
Nucleons
Electrons
The condition of diffraction from a crystal is given by
nλ = 2d Sin θ
λ = d Sin 2θ
λ = 2d Sin 2θ
nλ = d Sin θ
Biological shield in a nuclear reactor is generally provided to protect against the
α-rays
β-rays
Gamma rays & neutrons
Electrons
Oxyacetylene reducing flame is used while carrying out welding on
Alloy steel
Grey cast iron
Mild steel
High carbon steel
The yield point phenomenon observed in annealed low carbon steel is due to the presence of the following element.
Silicon
Carbon
Phosphorous
Chromium
Pick out the wrong statement.
Both annealing and normalising release the internal stresses of the material besides improving the mechanical properties
Low carbon steel does not respond to the heat treatment for hardening of the material, hence it is subjected to case hardening or surface hardening processes like cyaniding, carburising, nitriding etc., which produces high carbon outer layers resulting in increase of surface hardness
Induction hardening and flame hardening techniques are also used for surface hardening
Martempering of a material is a hardening process
A metal having a Poisson's ratio = 0.3 is elastically deformed under uniaxial tension. If the longitudinal strain = 0.8, then the magnitude of thickness strain is
-0.8
0.8
+0.08
-0.24
Percentage of argon (by volume) in dry atmospheric air is about
0.09
0.3
0.57
0.94
Coarse grained steels have
Low toughness
No tendency to distort
High density
Very high toughness
Young's modulus of a material is the measure of its
Stiffness
Malleability
Creep resistance
Tensile strength
Heat flow across a hollow sphere of inner radius 'r1' and outer radius 'r2' is directly proportional to
(r2 - r1)/r1. r2
r1. r2/(r2 - r1)
(r2 + r1)/r1. r2
r1. r2/(r2 + r1)
Which of the following performance characteristics of a S.I engine is not affected by the front end volatility of the petrol used?
Vapour locking
Hot starting
Spark plug fouling
All 'a', 'b' & 'c'
The dew point of moist air becomes __________ with decrease in its relative humidity.
Less than the wet bulb temperature
More than the wet bulb temperature
More than the dry bulb temperature
Equal to wet bulb temperature
The softness or hardness of a grinding wheel depends upon the type & amount of bonding material used. For general purpose cutter grinding __________ grinding wheel is normally used.
Hard
Soft
Silicon carbide
Aluminium oxide
What is the range of tempering temperature (°C) for most of the materials?
75-100
200-300
350-450
500-600
Materials having __________ lattice structure are usually the most ductile.
Body centred cubic (bcc)
Hexagonal close packed (hcp)
Face centred cubic (fcc)
None of these
The activity co-efficient of the solute in a dilute solution
Decreases with the increase of concentration of the solute
Increases with the increase of concentration of the solute
Remains constant
Is unity at infinite dilution
Powder metallurgy technique is used in the production of __________ tools.
Tungsten carbide
High carbon steel
High speed steel
Drilling
The delivery pressure of boiler feed water pump compared to the boiler steam pressure is
Same
Slightly less
Slightly more
Much more
Tesla metre per ampere (T. m/A) is the unit for the measurement of
Magnetic susceptibility
Magnetic moment
Permeability of free space
Flux density
Pressure exerted by a liquid depends upon its
Surface tension
Density
Viscosity
Buoyancy
Which of the following is the correct nature of shear stress distribution along the cross section in a horizontal circular pipe under steady state fluid flow condition?
Preheating before welding is done to
Make the plate softer
Burn oil & grease sticking to plate surfaces
Avoid plate distortion
Prevent cold cracks
Maximum change in the hardness of martensite occurs in the carbon content range of __________ percent in steel.
0.01 to 0.10
0.2 to 0.4
0.5 to 0.7
0.8 to 1.0
High relative humidity decreases the evaporative process and as the temperature is increased, the relative humidity decreases. The comfort range for human body is the ambient temperature of 22 to 27°C with relative humidity ranging from __________ percent.
5 to 10
15 to 25
45 to 50
75 to 80
Air-petrol ratio for maximum power generation in spark ignition engine is about
6 : 1
12 : 1
18 : 1
24 : 1