This set of Building Construction Questions and Answers for Campus interviews focuses on “Miscellaneous Materials – 2”.
1. The power to resist an electric stress is called as ___________
a) Dielectric strength
Explanation: The power to resist electric stress is called dielectric strength. Dielectric is used to refer to a substance that is capable of supporting electric stress.
2. Which of the following is not a property of a good electrical insulator?
a) It has high electrical resistance
b) It has a high dielectric strength
c) It has a high dielectric constant
d) It has a high thermal resistance
Explanation: A good electrical insulator has high electrical resistance and high thermal resistance. It has high dielectric strength and low dielectric constant.
3. Coal gas is obtained by thermal decomposition of coal in the presence of air at low temperature.
Explanation: Coal gas, natural gas and producer gas are some important gaseous fuels. Coal gas is obtained by thermal decomposition of coal in the absence of air at high temperatures.
4. Which of the following is not a solid fuel?
Explanation: A fuel is a substance that is capable of creating heat energy which can be put to industrial use. Fuels are classified into three groups depending on the state in which they occur. These are solid fuels, liquid fuels and gaseous fuels. Charcoal, coke and coal are examples of solid fuels while petroleum is a liquid fuel.
5. The percentage content of water and calcium sulphate in gypsum is _______ and _______ respectively.
a) 20.9, 79.1
b) 15.4, 84.6
c) 30.7, 69.3
d) 55.3, 44.7
Explanation: Gypsum is the hydrated sulphate of calcium and is a white crystalline substance. The percentage content of water and calcium sulphate in gypsum is 20.9 and 79.1 respectively.
6. Which of the following statements about gypsum is not correct?
a) The final setting time of gypsum is 30 minutes
b) The solubility of gypsum in water is very poor
c) Gypsum in insoluble in sulphuric acid
d) Gypsum is insoluble in hydrochloric acid
Explanation: The final setting time of gypsum is 30 minutes. The solubility of gypsum in water is very poor. Gypsum in insoluble in sulphuric acid but soluble in hydrochloric acid.
7. Plaster of Paris is __________
a) Double hydrate of aluminium sulphate
b) Double hydrate of calcium sulphate
c) Hemihydrate of calcium sulphate
d) Hemihydrate of aluminium sulphate
Explanation: Plaster of Paris is hemihydrate of calcium sulphate. On heating finely ground gypsum at a suitable temperature, it loses about 14.7% of its water content and forms plaster of Paris.
8. Which of the following should be added to the plaster of Paris in order to increase its setting time?
b) Potassium sulphate
c) Potassium nitrate
d) Citric acid
Explanation: To increase the setting time of the plaster of Paris, suitable retarders are added in it. Citric acid, clay, gum, glue, starch, etc. are all examples of such retarders.
9. The coefficient of heat conductivity of heat-insulating materials does not exceed _________
a) 0.18 kcal/m.hr.°C
b) 0.28 kcal/m.hr.°C
c) 0.38 kcal/m.hr.°C
d) 0.48 kcal/m.hr.°C
Explanation: The coefficient of heat conductivity of heat-insulating materials does not exceed 0.18 kcal/m.hr.°C. These materials are needed to give protection against heat and cold. They are generally porous.
10. Which of the following is not a solid lubricant?
Explanation: With the use of lubricants, easy motion of the moving parts of a machine is facilitated. There are two types of lubricants – solid lubricants and liquid lubricants. Graphite, mica and soapstone are examples of solid lubricants while grease is a liquid lubricant.
11. Which of the following statements about liquid lubricants is false?
a) They should be greasy in nature
b) Their melting point should be high
c) Their boiling point should be high
d) They should not contain any impurities
Explanation: Liquid lubricants should be greasy in nature and should not contain any impurities. Their boiling point should be high and melting point should be low.
12. Which of the following oils is obtained by boiling fats and other parts of cattle with water?
a) Lard oil
b) Whale oil
c) Neat’s foot oil
d) Tallow oil
Explanation: Neat’s foot oil is obtained by boiling fats and other parts of cattle with water. The specific gravity of this oil is 0.916. Neat’s foot oil is used for delicate mechanisms like clocks, sewing machines, etc.
13. Which of the following oils are obtained by mixing mineral oils with animal or vegetable oils?
a) Animal oils
b) Mineral oils
d) Blended oils
Explanation: Blended oils are obtained by mixing mineral oils with animal or vegetable oils. Blended oils are economical. Also, the mineral oils become less volatile when animal oils or vegetable oils are added to them.
14. Which of the following oils is obtained from the seed of rape plant?
a) Castor oil
b) Colza oil
c) Hazel-nut oil
d) Olive oil
Explanation: Colza oil is obtained from the seed of rape plant. This plant belongs to the cabbage family. Colza oil is used as a lubricant for delicate instruments.
15. Buna-S, Neoprene and Butyl are different trade names of _________
a) Natural rubber
b) Synthetic rubber
d) Animal oils
Explanation: Rubber can be either natural or synthetic. Buna-S, Neoprene and Butyl are different trade names of synthetic rubber. Synthetic rubber refers to the rubber-like materials produced by chemical processes.
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