5) A brass rod, 75.0 cm long andhaving a cross-sectional area of 2.50 cm2, condu

Question

5) A brass rod, 75.0 cm long andhaving a cross-sectional area of 2.50 cm2, conducts heat froma large

furnace at 375°C into a large coldwater bath at 10.0°C without losing any heat at the surface ofthe

rod. Steady state has beenestablished, and the thermal conductivity of brass is 109W/m · K.The

rate at which the entropy of thesystem (furnace plus water) is changing is closestto:

5)

A) 2.05 ×10-2W/K

B) 4.69 ×10-2W/K

C) 2.64 ×10-2W/K

D) 6.74 ×10-2W/K

E) 3.54 ×10-2W/K

Figure 20.4

A diesel engine operates reversibly onthe cycle abcda, using9.0 moles of an ideal gas. Paths bc and da areadiabatic processes.The operating temperatures ofpoints a, b,c, and d of thecycle are 375 K, 450 K, 432 K, and 250 K, respectively. Theadiabati constant of the gas is 1.50.

A) 23 B) 25 C) 27 D) 19 E) 21

Explanation / Answer

i would try to answer question #1. Question #2 i am unable to readthe diagram. the heat conduction equation is Q/t = kA(T)/d = (109)(2.5 x 10-4)(375-10)/.75 = 13.26 W the rate of increase of entropy for water is (Q/t)/Tcold = 13.26/283 = .0469 the rate of decrease of entropy for furnace is (Q/t)/Thot = 13.26/(273+375) = .0205 net rate of increase = .0469-.0205 = .0264 W/K so the answer is C

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