Use of flux during soldering is done to
Increase fluidity of solder by lowering its melting temperature
Prevent oxide formation
Wash away surplus solder
Full up the joint gap
Correct Answer :
B. Prevent oxide formation
Related Questions
Ammonia leakage in the refrigeration system is detected by
Sulphur stick, which on detection gives white smoke
Using chemical reagents
Its smell
Soap solution
Routing in production, planning & control is concerned with the
Sequence of operation to be performed
Progress of work performed
Authorisation of work to be performed
Balancing of load on machines
Maraging steels derive their strength from the following mechanism:
A fine, highly dislocated and strong martensite
Fine dispersions of inter-metallic of Fe, Ni, Ti etc
Fine dispersions of alloy carbides in a ferrite matrix
Fine dispersions of 
C nucleated on dislocations in austenite
Which of the, following is not associated with the functioning of a petrol engine?
Compression ignition system
Spark plug
Carburettor
Otto cycle
Nickel and __________ are the alloying element added in steel to increase its toughness.
Molybdenum
Chromium
Vanadium
Silicon
Boiler draught of 10 mm water column is equivalent to
1 kgf/m2
10 kgf/m2
10 kgf/mm2
1 kgf/mm2
The amount of different substances produced, when the same quantity of electricity is passed through different solutions are proportional to their
Equivalent weight
(Equivalent weight)2
Molecular weight
(Molecular weight)2
Nusselt number is related to the Reynolds number (Re) in turbulent & laminar flow respectively as
Re0.5, Re0.8
Re0.8, Re-0.5
Re0.8, Re0.5
Re-0.8, Re0.5
Which of the following materials does not form adherent oxide film on surface?
Copper
Nickel
Aluminium
Gold & silver
Strain hardening effect in a metal subjected to cold working is due to the __________ mechanism.
Fracture
Dislocation
Slip
Twinning
Brittleness induced due to the presence of sulphur in steel can be reduced by adding
Manganese
Magnesium
Vanadium
Copper
Normalising of an object does not
Refine coarse grain structure obtained during hot working
Improve ductility
Improve yield strength
Improve mechanical properties
Which of the following forces does not act on a fluid at rest?
Viscous force
Gravity force
Hydrostatic force
Surface tension force
The maximum stress below which a material can withstand an infinite number of cycle of stress, is termed as the
Fatigue strength
Creep strength
Resilience
Endurance limit
To improve the machinability of steel, it is generally subjected to
Spheroidising
Tempering
Normalising
Annealing
Pipelines carrying various utilities in chemical industries are identified by their colour codes. The color of pipeline carrying steam is
Black
Silver grey
Green
Yellow
Silicon percentage in acid resistant cast iron is about
4
8
14
20
A steam carrying pipeline is insulated with two layers of insulating materials with the inferior insulation material forming the inner part. If the two insulating layers are interchanged, the heat conducted will
Increase
Decrease
Remain unaffected
May increase or decrease; depends on the thickness of each layer
The phenomenon occurring during explosion of a hydrogen bomb is
Nuclear fission
Nuclear fusion
A combination of both nuclear fission & fusion
None of these
A dense structure of grinding wheel is not used for the
Ductile material
Hard materials
Brittle materials
Finishing cuts
Strain hardening effect in metals subjected to cold working is due to the __________ mechanism.
Slip
Fracture
Winning
Dislocation
An approximately __________ process exemplifies the flow of a gas through a very long pipe of uniform cross-section.
Adiabatic
Isothermal
Isentropic
Isochoric
__________ cannot increase the fatigue strength of a material.
Grain refining
Grain coarsening
Surface hardening
Shot peening
Potable water means the water used for
Fire-fighting
Cooling
Drinking
Evaporation to produce steam
What is the range of tempering temperature (°C) for most of the materials?
75-100
200-300
350-450
500-600
Which of the following processes follows the hardening process for reducing the hardening strains & increasing the toughness of the steel part?
Anodising
Tempering
Carburising
Annealing
Metalloids
Are good conductor of heat & electricity
Act as electron donors with metals & as electron acceptor with non-metals
Are not necessarily solids at room temperature
Are compounds that exhibit both metallic & non-metallic properties to some extent and are exemplified by elements like germanium, silicon & boron
Photographic plates are coated with
Silver nitrate
Silver halide
Calcium silicate
Metallic silver
Main constituent of bone ash is
Ammonium phosphate
Calcium phosphate
Animal charcoal
Ammonium sulphate
The ratio of thermal & electrical conductivity is same for all the metals at the same temperature; and at around room temperature, this ratio is proportional to(where, T = absolute temperature, °K)
T
1/T
T2
1/T2