Chemical Engineering Basics

831. While the recrystallisation temperature for pure metals is 0.3 T_m, the same for alloys is equal to __________ × T_m (where, T_m Melting temperature).

1. 0.25
2. 0.45
3. 0.7
4. 0.95

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832. While the thermosetting polymers are amorphous in nature, the thermoplastic polymers are either amorphous or crystalline. The crystalline polymers are characterised by the

1. Low impact strength
2. High flexibility
3. Better finish and surface appearance
4. High plastic deformation

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833. Window panes of aeroplanes are normally made of

1. Perspex (PMMA)
2. Teflon (PTFE)
3. Bakelite (phenol formaldehyde)
4. Polystyrene

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834. With decrease in the grain size of a material, its creep resistance

1. Increases
2. Decreases
3. Remain constant
4. Either (A) or (B); depends on the material

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835. With increase in __________ Knocking tendency in a spark ignition petrol engine decreases.

1. Supercharging
2. Wall temperature
3. Compression ratio
4. Engine speed

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836. With increase in annealing temperature, the following defect density decreases.

1. Vacancy
2. Dislocation
3. Grain boundary
4. All of these

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837. With increase in compression ratio, the volumetric efficiency of air compressor

1. Increases
2. Decreases
3. Remain same
4. May increase or decrease (depends on the suction pressure)

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838. With increase in impurities in metals, their corrosion resistances

1. Increase
2. Decrease
3. Remain same
4. May increase or decrease; depending on the type of metal

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839. With increase in steam pressure, its specific volume decreases

1. Rapidly first and then slowly
2. Linearly
3. Slowly first and then rapidly
4. Exponentially

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840. With increase in temperature, the electrical conductivity of a __________ decreases.

1. Semi-conductor
2. Metal or alloy
3. Dielectric
4. None of these

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