Materials and Construction

321. Silicon percentage in iron castings to have maximum hardness should be about

1. 0.3
2. 0.5
3. 0.8
4. 2.5

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322. Silicone rubber is not resistant to the corrosive action of

1. Sulphuric acid (10%)
2. Sulphuric acid (95%)
3. Ether
4. Both (B) and (C)

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323. Slow and progressive deformation of a material with time under constant stress is called

1. Creep
2. Erosion
3. Resilience
4. None of these

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324. Slow plastic deformation of metals under a constant stress is termed as _________ failure.

1. Fatigue
2. Endurance
3. Creep
4. None of these

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325. SO3 is absorbed using H2SO4 in a

1. Cast iron packed tower
2. Stainless steel plate tower
3. Packed steel tower lined with acid proof bricks
4. None of these

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326. Soap kettle used in the production of laundry soap is made of

1. Steel with top section nickel clad or stainless steel
2. Cast iron
3. Nickel
4. Concrete

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327. Softening of hardened steel is done by its

1. Normalising
2. Tempering
3. Annealing
4. Carburising

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328. Softness of silver can be converted into hardness by alloying it with small quantity of

1. Copper & nickel
2. Zinc
3. Aluminium
4. Tin

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329. Spark plugs are made of

1. High alumina ceramic
2. Metallic carbides
3. Corundum
4. Carborundum

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330. Spark plugs, ignition tubes and electrodes are made of nickel _________ alloys.

1. Beryllium
2. Manganese
3. Copper
4. Iron

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