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4

Damage to metal surface by mechanical action is called

A. Pitting

B. Corrosion

C. Erosion

D. None of these

Correct Answer :

C. Erosion


Related Questions

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4

Use of water as a manometric liquid suffers from the disadvantage of its

A. Low vapour pressure

B. Corrosive nature

C. High vapour pressure

D. High boiling point

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4

Sacrificial anode method is used in the protection of pipelines which are buried underground. Sacrificial anode

A. Occurs higher in the electro-chemical series of metals

B. Is exemplified by magnesium plate

C. Is much cheaper than the cathodic base material to be guarded against corrosion

D. All (A), (B) & (C)

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4

Electrometallurgical methods of metal extraction is normally used for those metals

A. Whose oxide/ore is not reduced by carbon

B. Which fall in the category of alkali & alkaline earth metals

C. Which stands higher in the electrochemical series of the metal

D. All (A), (B) & (C)

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4

Cold cracking in the heat affected zone of a high strength steel weld can take place because of the

A. Retained austenite

B. Martensite formation

C. Relatively high sulphur content in the base metal

D. Sufficient hydrogen present in the welding arc

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4

Which of the following mainly decides the current to be employed is arc welding?

A. Electrode size

B. Plate thickness

C. Voltage across the arc

D. Welded portion length

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4

Evaporative cooling process employs a combination of cooling and humidification in which the

A. Sensible heat is added

B. Sensible heat is removed and the latent heat is added

C. Latent heat is removed

D. Sensible heat is added and latent heat is removed

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4

Which of the following low melting alloy containing bismuth and lead is used for electric fuse?

A. Wood's metal

B. Babbitt metal

C. Monel metal

D. Duralumin

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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

Baffles provided on the shell side of a shell and tube heat exchanger are meant for

A. Providing support for the tubes

B. Improving heat transfer

C. Both 'a' & 'b'

D. Preventing the fouling of tubes & stagnation of shell side fluid

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4

Which of the following test is used for distinguishing among dry oils, semi-drying oils and non drying oils?

A. Elaiden test

B. Reichert-Meissl value test

C. Hunter value test

D. Iodine value test

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4

A material subjected __________ must have high resilience.

A. Shock loading

B. Vibration

C. Fatigue

D. Tension

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4

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?

A.

B.

C.

D.

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4

__________ joint is usually used for joining cast iron pipes mostly used for temporary pipelines, where it may be necessary to dismantle & reassemble the pipeline very frequently.

A. Collar

B. Flanged

C. Bell and Spigot

D. Expansion

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4

Which of the following materials does not form adherent oxide film on surface?

A. Copper

B. Nickel

C. Aluminium

D. Gold & silver

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4

Which of the following is not a characteristic observed in material failure by fatigue fracture?

A. Plastic deformation of material does not occur

B. Initiation of crack from below the surface does not occur

C. Initiation of crack occurs on the surface of the machine part

D. Presence of both rough & smooth zone with conchoidal markings in smooth zone of the surface

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4

The most prominent single cause of corrosion in boiler-tubes, drums, economisers and steam superheaters in a thermal power plant boiler is the

A. Water alkalinity & leakage

B. Hydrazine addition during feed water treatment

C. Release of non-condensable gas from water in the boiler

D. Scale formation

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4

Tempering of a material does not improve its

A. Machinability

B. Toughness

C. Internal stress level

D. Softness

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4

Which of the following is prone to cup and cone fracture?

A. Cast iron

B. Soft brass

C. Round specimen of ductile metal

D. Flat tensile specimen of ductile metal

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4

Heat transfer by __________ is almost absent in case of fluidised bed drying operation.

A. Radiation

B. Conduction

C. Convection

D. Both (B) & (C)

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4

Out of the following, maximum temperature drop for a given heat flow & for the same thickness will be in the case of

A. Steel

B. Glass wood

C. Copper

D. Fireclay bricks

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4

Which of the following is not the commercial name of poly-methyl-methacrylate (PMMA)?

A. Styrofoam

B. Lucite

C. Perspex

D. Plexiglass

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4

What is the value of entropy at 273°K?

A. 0

B. 1

C.

D. None of these

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4

The following thermocouple may be used for measuring temperature upto 1873°K.

A. Chromel-alumel

B. Copper-constantan

C. Platinum-platinum rhodium

D. Iron-constantan

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4

Dies for wire drawing are generally made of

A. Mild steel

B. Stainless steel

C. Carbides

D. High carbon steel

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4

The maximum stress below which a material can withstand an infinite number of cycle of stress, is termed as the

A. Fatigue strength

B. Creep strength

C. Resilience

D. Endurance limit

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4

The leaching solvent used in Baeyer's process for the purification of bauxite is

A. Ammonium hydroxide

B. Sodium carbonate

C. Sodium hydroxide

D. Ammonium carbonate

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4

The condition of diffraction from a crystal is given by

A. nλ = 2d Sin θ

B. λ = d Sin 2θ

C. λ = 2d Sin 2θ

D. nλ = d Sin θ

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4

Hydrogen can be

A. Used in I.C. engines as fuel

B. Liquefied & stored under cryogenic conditions

C. Produced by electrolysis of water

D. All (A), (B) & (C)

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4

Thermal diffusivity of a substance is proportional to (where, k = Thermal conductivity)

A. 1/k

B. k

C. k2

D. 1/k2

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4

Cassiterite is an ore of

A. Tin

B. Lead

C. Molybdenum

D. Chromium