On a cold winter day, the outside temperature is -20°C and the inside temperature is maintained at 20°C. There is a net heat flow to the outside through the walls, roof, etc., of 25 kW. What is the rate of increase of the entropy of the universe as a result of this?
A) 13 W/K
B) 25 W/K
C) 85 W/K
D) 99 W/K
E) 0 W/K

Question

Quizplus · Accepted Answer

The rate of increase of entropy of the universe is calculated using the formula: ΔS = Q/T. The heat flow is 25 kW, and the temperatures are 20°C (293 K) inside and -20°C (253 K) outside. The entropy increase is due to the heat flow to the colder reservoir: ΔS = 25000 W / 253 K - 25000 W / 293 K ≈ 13 W/K.

On a Cold Winter Day, the Outside Temperature Is -20°C