E-PolyLearning

21. Mark the matter with least value of thermal conductivity
a. Air
b. Water
c. Ash
d. Window glass
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Answer: (a).Air

22. Which one of the following forms of water have the highest value of thermal conductivity?
a. Boiling water
b. Steam
c. Solid ice
d. Melting ice
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Answer: (c).Solid ice

23. The average thermal conductivities of water and air conform to the ratio
a. 50:1
b. 25:1
c. 5:1
d. 15:1
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Answer: (b).25:1

24. Identify the very good insulator
a. Saw dust
b. Cork
c. Asbestos sheet
d. Glass wool
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Answer: (d).Glass wool

25. Most metals are good conductor of heat because of
a. Transport of energy
b. Free electrons and frequent collision of atoms
c. Lattice defects
d. Capacity to absorb energy
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Answer: (b).Free electrons and frequent collision of atoms

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