Electrolytic reduction cell used for conversion of calcined Al2O3 to Al is a carbon lined furnace operating at 800-900 °C. The purpose of electric current supplied to the furnace is to
Achieve very high purity of aluminium (99.9%)
Keep the electrolyte in liquid condition by the generation of heat
Electrolytically dissociate alumina
Both (B) & (C)
Correct Answer :
D. Both (B) & (C)
Related Questions
Which of the following terminology is used for the temperature at which new grains are formed in a metal?
Eutectic temperature
Lower critical temperature
Recrystallisation temperature
Upper critical temperature
Temperature attained in soldering of metals is about __________ °C.
150-300
400-500
650-800
1000-1100
The cooling rate required to freeze 1 ton of water at 0°C into ice at 0°C in 24 hours is __________ BTU/hr.
100
200
1000
2000
The capacity of a spring to store energy is called the spring form co-efficient. Stiffness of a spring is measured by the
Ability to absorb shock
Capacity to store energy
Ratio of the wire & coil diameters
Load to produce unit deflection
Reduction in the grain size reduces the __________ of the material.
Fatigue resistance
Tensile strength
Creep resistance
All (A), (B) & (C)
Mild steel has __________ crystal lattice structure.
Face centred cubic (fcc)
Body centred cubic (bcc)
Orthorhombic
Cubic
Saturated steam at a pressure of 25 kg/cm2 is throttled to attain 5 kg/cm2. Then the outcoming steam will be
Wet
Saturated
Superheated
None of these
Titanium is added to molten aluminium alloys before casting for the purpose of
Grain refinement
Increasing corrosion resistance
Reducing porosity
Improving fluidity
The units of the rate constant for a second order reaction are
The pressure drop per unit length for laminar flow of fluid through a long pipe is proportional to (where, A = cross-sectional area of the pipe & D = Diameter of the pipe)
A
D
1/A
1/A2
Probability of cavitation occuring becomes very high, when the local __________ resulting in water bubbles formation, which on rupture cause cavitation
Pressure falls below the vapour pressure
Pressure becomes very high
Temperature becomes low
All 'a', 'b' & 'c'
Primary designation of steel is based on its
Hardness & tensile strength
Carbon content
Iron content
Alloying elements content
Carbide tipped cutting tools are manufactured by powder metallurgy techniques and have a composition of
90% tungsten carbide and 10% cobalt
70% aluminium oxide & 30% silica
30% nickel, 15% chromium & 55% tungsten
65% tungsten & 35% zirconium
Diamagnetic materials
Are magnetised by eddy currents only
Are non-magnetic and cannot be magnetised
Are magnetised in direction opposite to the magnetic field
Can be magnetised in one direction only
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
Electrostatic separation of minerals from each other is based on their differences in the following property.
Densities
Magnetic permeabilities
Electrical conductivities
Hardness
A reduction in thermal resistance during heat transfer does not occur in the
Convection heat transfer by stirring the fluid and cleaning the heating surface
Conduction heat transfer by reduction in the material thickness and increase in the thermal conductivity
Radiation heat transfer by increasing the temperature and reducing the emissivity
None of these
Copper deposits are found in India at the following location:
Kudremukh
Kolar
Khetri
Ramagundam
A fluid is termed as the Newtonian fluid, when the shear stress is __________ the velocity gradient.
Independent of
Inversely proportional to
Directly proportional to
None of these
The escape velocity of a body on earth which is independent of its mass is about __________ km/second.
3
7
11
15
Pick out the wrong statement.
Molecules with symmetrical arrangements (e.g. CH4 or CCl4) are non-polar
Generally, non-polar compounds are chemically inactive, conduct electricity poorly and do not ionise
Most of the hydrocarbons are non-polar
None of these
'Ice point' is designated on Fahrenheit temperature scale by
0°
32°
62°
212°
In the formation of cermets, the ratio of ceramic material to metallic material is usually 80:20. Which of the following is a cermet?
Zirconia
Alumina
Bakelite
Tungsten carbide
Consider an ideal solution of components A and B. The entropy of mixing per mole of an alloy containing 50% B is
R ln 2
-R ln 2
3 R ln 2
-3R ln 2
At absolute zero temperature, for any reaction involving condensed phases
Δ G° = 0 , Δ H° = 0
Δ H° = 0 , Δ S° = 0
Δ S° = 0 , Δ E° = 0
Δ S° = 0 , Δ Cp° = 0
Holes for riveting purposes should be preferably made by
Cutting torch
Drilling
Punching
None of these
Heat transfer by __________ is almost absent in case of fluidised bed drying operation.
Radiation
Conduction
Convection
Both (B) & (C)
Two wires of the same radius & material having length in the ratio of 1 : 2 are stretched by the same force. The strain produced in the two wires will be in the ratio of
1 : 1
1 : 2
2 : 1
1 : 4
An alloy of Fe - 0.4 % C is
Cast iron
Hypo-eutectoid steel
Hyper-eutectoid steel
Eutectoid steel
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'