E-PolyLearning

21. “Radiation cannot be affected through vacuum or space devoid of any matter”. True or false
a. True
b. False
c. May be
d. Can't say
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Answer: (b).False

22. A composite slab has two layers having thermal conductivities in the ratio of 1:2. If thickness is same for each layer then the equivalent thermal conductivity of the slab would be
a. 1/3
b. 2/3
c. 2
d. 4/3
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Answer: (d).4/3

23. A composite wall of a furnace has two layers of equal thickness having thermal conductivities in the ratio 2:3. What is the ratio of temperature drop across the two layers?
a. 2:3
b. 3:2
c. 1:2
d. log e 2 : log e 3
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Answer: (b).3:2

24. Typical examples of heat conduction through cylindrical tubes are not found in
a. Power plants
b. Oil refineries
c. Most process industries
d. Aircrafts
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Answer: (d).Aircrafts

25. The rate of heat conduction through a cylindrical tube is usually expressed as
a. Per unit length
b. Per unit area
c. Only length
d. Only area
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Answer: (a).Per unit length

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