E-PolyLearning

6. The temperature distribution in a large thin plate with uniform surface temperature will be
(Assume steady state condition)
a. Logarithmic
b. Hyperbolic
c. Parabolic
d. Linear
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Answer: (d).Linear

7. Let us assume two walls of same thickness and cross-sectional area having thermal conductivities in the ratio 1/2. Let us say there is same temperature difference across the wall faces, the ratio of heat flow will be
a. 1
b. 1/2
c. 2
d. 4
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Answer: (b).1/2

8. The interior of an oven is maintained at a temperature of 850 degree Celsius by means of a suitable control apparatus. The oven walls are 500 mm thick and are fabricated from a material of thermal conductivity 0.3 W/m degree. For an outside wall temperature of 250 degree Celsius, workout the resistance to heat flow
a. 0.667 degree/W
b. 1.667 degree/W
c. 2.667 degree/W
d. 3.667 degree/W
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Answer: (b).1.667 degree/W

9. A plane slab of thickness 60 cm is made of a material of thermal conductivity k = 17.45 W/m K. Let us assume that one side of the slab absorbs a net amount of radiant energy at the rate q = 530.5 watt/m². If the other face of the slab is at a constant temperature t₂ = 38 degree Celsius. Comment on the temperature with respect to the slab?
a. 87.5 degree Celsius
b. 32 degree Celsius
c. 47.08 degree Celsius
d. 32.87 degree Celsius
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Answer: (c).47.08 degree Celsius

10. The rate of heat transfer for a plane wall of homogenous material with constant thermal conductivity is given by
a. Q = kA (t₁-t₂)/δ
b. Q = 2kAx/ δ
c. Q = 2kAδx
d. Q = 2k/δ x
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Answer: (a).Q = kA (t₁-t₂)/δ

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