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4

The Al2O3 content of cryolite in Hall- Heroult cell is maintained between __________ percent.

A. 2-5

B. 18-20

C. 12-15

D. 6-12

Correct Answer :

A. 2-5


Related Questions

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4

Basicity of the slag in Indian blast furnace is in the range of

A. 0.7-1.0

B. 1.1-1.4

C. 1.5 - 1.8

D. 2.0 - 2.5

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4

A material is capable of resisting softening at high temperature, because of its property termed as

A. Hot temper

B. Hot hardness

C. Fatigue

D. Creep

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4

Damage to metal surface by mechanical action is called

A. Pitting

B. Corrosion

C. Erosion

D. None of these

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4

Energy of the sun arises mainly from __________ reactions.

A. Fusion

B. Fission

C. Combustion

D. None of these

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4

Which of the following terminology is used for the temperature at which new grains are formed in a metal?

A. Eutectic temperature

B. Lower critical temperature

C. Recrystallisation temperature

D. Upper critical temperature

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4

While the oxy-acetylene flame produces a temperature of 3200°C, the temperature produced by oxy-hydrogen flame is about __________ °C.

A. 1800

B. 2000

C. 2400

D. 3000

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4

The usual energy consumption in electric arc furnace steel making is __________ KWh/ton of steel.

A. 60 - 100

B. 400 - 700

C. 1200 -1500

D. 2000 - 2300

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4

The main constituent of bones is

A. CaF2

B. Ca3(PO4)2

C. CaCO3

D. CaCl2

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4

Velocity of a gas in sound is not proportional to (where, T = Absolute temperature of the gas. P = Absolute pressure of the gas. y = Ratio of specific heats (Cp/Cv) ρ = specific weight of the gas)

A. √T

B. 1/√P

C. √y

D. 1/√ρ

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4

Factor of safety in machine design is defined as the ratio of ultimate stress to __________ stress.

A. Working

B. Bearing

C. Yield

D. None of these

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4

Air-petrol ratio for maximum power generation in spark ignition engine is about

A. 6 : 1

B. 12 : 1

C. 18 : 1

D. 24 : 1

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4

Powder metallurgy process does not make metal powder by

A. Atomisation

B. Grinding/milling

C. Hammering

D. Electrolytic deposition

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4

The atmospheric temperature during melting of ice/snow (in the atmosphere)

A. Decreases

B. Increases

C. Remain same

D. May increase or decrease; depends on the altitude where snow melts

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4

Annealing of cast iron

A. Softens it to facilitate machining

B. Decreases the free carbon

C. Increases the strength

D. None of these

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4

When the wet steam is throttled but still remains wet at the exit of the throttle valve, then its temperature & dryness fraction respectively

A. Decreases & increases

B. Increases & increases

C. Increases & decreases

D. Decreases & decreases

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4

Hot dipping process is used for coating a low melting point metal (e.g. Pb, Sn, Zn) on iron, steel & copper having relatively higher melting points. Which of the following is not a hot dipping process?

A. Galvanising

B. Tinning

C. Sherardizing

D. None of these

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4

Limestone addition in the blast furnace is done to flux __________ present in the raw materials.

A. SiO2

B. Al2O3

C. MnO2

D. P

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4

Magnetic permeability of iron is increased by its

A. Decarburising

B. Alloying with cobalt

C. Purification

D. Alternate heating & cooling

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4

Which of the following forces does not act on a fluid at rest?

A. Viscous force

B. Gravity force

C. Hydrostatic force

D. Surface tension force

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4

According to maximum shear stress failure criterion, yielding in material occurs, when the maximum shear stress is equal to __________ times the yield stress.

A. 0.5

B. 2

C. √2

D. √3/2

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4

Which of the following relationships is correct for relating the three elastic constants of an isotropic elastic material (where, E = Young's modulus, G = Modulus of rigidity or shear modulus v = Poisson's ratio)?

A. E = 2G (1 + v)

B. E = G (1 + v)

C. E = G (1 + v)/2

D. E = 2G (1 + 2v)

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4

Maximum heat dissipation occurs from a steel wire (k = 0.5 W/m. k) of 15 mm diameter exposed to air (h = 20W/m2 .k), when the insulation thickness is __________ mm.

A. 15

B. 25

C. 10

D. 30

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4

Cold chisel & hammers are made of

A. High speed steel

B. High carbon steel

C. Forged steel

D. Mild steel

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4

The thermodynamic law, = constant, is not followed by the

A. Free expansion of an ideal gas

B. Adiabatic expansion of steam in turbine

C. Adiabatic compression of air

D. Ideal compression of air

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4

For the Stoke's law to be valid in the case of a falling sphere in a fluid, the

A. Reynolds number (based on sphere diameter) should be < 1

B. Flow around the sphere should be in turbulent region

C. Sphere must be metallic

D. Fluid density should be constant

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4

A high pressure boiler generates steam at a pressure greater than __________ kg/cm2.

A. 10

B. 30

C. 50

D. 80

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4

The 'transition temperature' for ductile to brittle behaviour of steel increases with increase in the __________ content in steel.

A. Carbon

B. Manganese

C. Both 'a' nor 'b'

D. Neither 'a' nor 'b'

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4

Increase in temperature, in general results in the

A. Decrease in the viscosities of both liquids & gases

B. Increase in the viscosities of both liquids & gases

C. Increase in the viscosity of liquids and decrease in that of gases

D. Decrease in the viscosity of liquids and increase in that of gases

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4

Out of the following, the joint produced by __________ has the lowest strength.

A. Soldering

B. Welding

C. Brazing

D. Riveting

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4

What happens, when SO2 is passed through a solution of H2S in water?

A. Precipitation of sulphur takes place

B. H2SO3 is formed

C. Oleum is formed

D. None of these