Thermal Physics | 231309 - The question is on the imag QUESTION -askIITians

christopher Grade: 12th pass

        The question is on the imagQUESTION 1 (10 marks)
Calculate the rate at which body heat is conducted through the clothing of a skier in a steady-state process, given the following data: the body surface area is 1.8 m2, and the clothing is 1.0 cm thick; the skin surface temperature is 33􏰓 °C and the outer surface of the clothing is at 1.0 °C; the thermal conductivity of the clothing is 0.040 W/m.K
 
QUESTION 2 (15 marks)
A loaf of freshly baked bread is left to cool on a cooling rack. The dimension of the loaf is as described in the Figure 1, and its surface temperature is 120 °C. The temperature of the air is 20 °C, and the convection coefficient from the loaf to air is 10 W/m2K. Emissivity of the bread is 0.76, and its conductivity is 0.121.
 loafFigure1: Loaf of Bread
 
QUESTION 3 (10 marks)
An engine transfers 20.0 × 103 J of energy from a hot reservoir during a cycle and transfers 15.0 × 103 J as exhaust to a cold reservoir. Calculate the:
	amount of work done in one cycle                                                     (4 marks)
	efficiency of the engine                                                                      (6 marks)
QUESTION 4 (5 marks)
Explain why the entropy of the universe increases in all real processes?
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8 months ago

Answers : (1)

Arun

21571 Points

							Dear student
 
Please ask only one question in one thread.
 
1.)
 
 ) (305 K) / (0.012 m)= 1830 WFrom the above observation we conclude that, the rate H at which heat flows out through the clothing of a skier would be 1830 W.² for the area A, 305 K for temperature difference ΔT and 0.012 m for thickness Δx and 0.040 W/m. K for the thermal conductivity k in the equation H = kA ΔT/ Δx,H = kA ΔT/ Δx= (0.040 W/m. K) (1.8 m²Temperature difference, ΔT = (skin surface temperature) – (outer surface temperature of clothing)= 33̊ C – 1̊ C= 32̊ C= (32+273) K= 305 KThickness, Δx = 1.2 cm= (1.2 cm) (1 m/100 cm)= 0.012 mTo find out the rate H at which heat flows out through the clothing of a skier, substitute 1.8 m²Surface area of the body,A = 1.8 m

8 months ago

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