| 1. | The diagram shows heat conduction through a plane wall. The surface temperature is 475 K and it radiates heat to the surroundings at 335 K. If thermal conductivity of the material is 12.5 W/m degree, find the temperature gradient. Let convective coefficient be 80 W/m² degree and radiation factor is 0.9
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| a. | – 1052.4 degree celsius |
| b. | – 2052.4 degree celsius |
| c. | – 3052.4 degree celsius |
| d. | – 4052.4 degree celsius |
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Answer: (a).– 1052.4 degree celsius
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| 2. | From the concept of kinetic theory, mean travel velocity of the gas molecules is prescribed by the relation
(Where, G = Universal gas constant M = Molecular weight of the gas T = Absolute temperature) |
| a. | V = (3M/GT)⅟₂ |
| b. | V = (3GT/M)⅟₂ |
| c. | V = (6T/GM)⅟₂ |
| d. | V = (3GT/2M)⅟₂ |
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Answer: (b).V = (3GT/M)⅟₂
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| 3. | Low temperature insulation are used when the enclosure is at a temperature lower than the ambient temperature. Which one of the following is not a low temperature insulation? |
| a. | Asbestos |
| b. | Cork |
| c. | Cattle hair |
| d. | Slag wool |
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Answer: (a).Asbestos
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| 4. | The value of Lorenz number in 10¯⁸ W ohms/K² is |
| a. | 2.02 |
| b. | 2.35 |
| c. | 2.56 |
| d. | 2.45 |
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Answer: (d).2.45
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| 5. | Consider the following parameters
(i) Composition (ii) Density (iii) Porosity (iv) Structure Then, thermal conductivity of glass wool varies from sample to sample because of variation is |
| a. | 1 and 2 |
| b. | 1, 2, 3 and 4 |
| c. | 1 and 3 |
| d. | 1, 2 and 3 |
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Answer: (b).1, 2, 3 and 4
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