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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
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

2. From the concept of kinetic theory, mean travel velocity of the gas molecules is prescribed by the relation
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

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

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

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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