Chemical Engineering Basics

481. Pick out the wrong statement about nucleate boiling.

1. Bubble generation is by expansion of entrapped gas/vapour at small cavities in the surface
2. Surface temperature is greater than the saturation temperature of the liquid
3. Heat transfer from the surface of the liquid is less than that in film boiling
4. The temperature is less than that of film boiling

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482. Pick out the wrong statement about the machinability of metals. Machinability of a metal

1. Decreases with increase in strain hardening tendencies
2. Decreases with increase in hardness, in general
3. Depend on the composition, microstructure and physical & mechanical properties
4. Decreases with increases in tensile strength & decrease in grain size

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483. Pick out the wrong statement.

1. Cold cracking of a weld is due to the presence of hydrogen gas in the weld
2. True stress is given by, σ = σE (1 + εE), where σE and εE are engineering stress and engineering strain respectively
3. Phosphorous can be easily recovered in the iron blast furnace
4. High residual stress at the surface is beneficial for fatigue properties of a material

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484. Pipelines carrying various utilities in chemical industries are identified by their colour codes. The color of pipeline carrying steam is

1. Black
2. Silver grey
3. Green
4. Yellow

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485. Plants produce carbohydrates from the CO2 present in the atmosphere by

1. Polymerisation
2. Photochemical reaction
3. Oxidation
4. None of these

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486. Plasma is

1. A high temperature neutral gas
2. Nothing but ionised gas
3. A source of steady and highest controllable pressure
4. Formed at very low temperature

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487. Plastics as a material of construction suffer from the drawback of low

1. Machinability
2. Density
3. Strength
4. Plastic deformation

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488. Potable water means the water used for

1. Fire-fighting
2. Cooling
3. Drinking
4. Evaporation to produce steam

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489. Powder metallurgy is used to produce

1. High precision components with complex cavities and sharp features
2. Components of large size
3. Porosity free components
4. Components of such alloys whose constituents do not form alloys readily

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490. Powder metallurgy process does not make metal powder by

1. Atomisation
2. Grinding/milling
3. Hammering
4. Electrolytic deposition

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