| 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
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| 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
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| 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
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| 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
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| 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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