Electrochemical corrosion can occur, only if __________ is present in contact with metal.
Air
Oxygen
Liquid medium
Gaseous medium
Correct Answer :
C. Liquid medium
Related Questions
Silicon percentage in acid resistant cast iron is about
4
8
14
20
Addition of silicon to cast iron
Promotes graphite module formation
Improves its ductility
Does not promote graphite flakes formation
Increases the fluidity of molten metal
Constituents of stellite are
Zinc, copper & nickel
Cobalt, chromium & tungsten
Zinc, aluminium & nickel
Nickel, cobalt & vanadium
The effect of friction on the flow of steam through a nozzle is to decrease the __________ of steam.
Wetness
Mass flow rate
Both 'a' & 'b'
Neither 'a' nor 'b'
The trace metal present in insulin is
Cu
Zn
Fe
Ni
When dry bulb temperature & wet bulb temperature of moist air is the same, it means that the
Partial pressure of water vapour is less than the total pressure
Humidity is < 100% & dew point temperature of air has not reached
Dew point temperature of air has not reached & air is not saturated fully
Air is fully saturated
The minimum temperature to which the water can be cooled in a cooling tower is the __________ temperature of air.
Ambient
Dry bulb
Dew point
Wet bulb
Vernier calipers cannot be used to measure the
I.D. & O.D. of the shaft
Thickness of parts
Depth of holes
Clearance between two mating surfaces
With increase in __________ Knocking tendency in a spark ignition petrol engine decreases.
Supercharging
Wall temperature
Compression ratio
Engine speed
An oxidation process is accompanied with decrease in the
Number of electrons
Oxidation number
Number of ions
All (A), (B) & (C)
Elimination of brittleness resulting from welding of saw blades is done by __________ of the welded portion.
Annealing
Toughening
Work hardening
Tempering
Globular form of cementite is formed during the __________ process.
Spheroidising
Hardening
Annealing
Normalising
As the fluid flow rate increases, the float of the Rotameter
Rises in the tube
Rotates at higher speed
Rotates at lower speed
Drops down in the tube
Dephosphorization of molten pig iron is favoured by
Oxidising and basic slag
Reducing and basic slag
High activity co-efficient of phosphorous in metal
Oxidising and neutral slag
A material being tested for endurance strength is subjected to the __________ load.
Impact
Completely reversed
Dynamic
Static & dynamic
The 'laughing gas' is
Nitrous oxide
Nitric oxide
Nitrogen trioxide
Nitrogen pentoxide
In chemical dehumidification process
Wet bulb temperature increases
Dry bulb temperature remains constant
Dew point temperature increases
Dry bulb temperature increases
Pearlite comprises of
87% cementite & 13% Fe
87% ferrite & 13% cementite
93.33% ferrite & 6.67% C
87% ferrite & 13% C
Basic open hearth furnace (BOF) is not used for producing __________ steel.
Killed
Rimming
High alloy
None of these
Gas turbine normally employs a constant __________ cycle.
Pressure
Temperature
Volume
None of these
Lead is poured into the joint between two __________ pipes.
Mild steel
Concrete
Cast iron
Asbestos cement
__________ is the process used for setting up compressive stresses in the surface of a metal to improve its fatigue strength.
Lancing
Shot peening
Slugging
Spinning
The life of a ball bearing is inversely proportional to
(Load)1
(Load)2
(Load)3
(Load)0.33
The size of the tetrahedral void in the closest packing of atoms is __________ that of the octahedral void.
Equal to
Greater than
Less than
Either (A), (B) or (C); depends on the size of atom
Referring to the periodic table of elements, it is found that with increasing atomic number. The atomic size in the same
Period increases
Period decreases
Group increases
Both 'b' & 'c'
The most suitable material for die casting is
Iron
Copper
Steel
Nickel
__________ is the trade name assigned to a nonferrous cast alloy composed of cobalt, chromium & tungsten.
Stellite
High speed steel
Cermet
Alnico
Suitability of steel for its use in cable is judged by its strength in
Tension
Compression
Torsion
Shear
Which of the following is not a dielectric material?
Cotton, silk and paper
Asbestos, glass, porcelain and mica
Rubber and polymeric resins
All refractory materials
Out of the following, maximum temperature drop for a given heat flow & for the same thickness will be in the case of
Steel
Glass wood
Copper
Fireclay bricks