1. In an electrically heated home, the temperature of the ground in contact with
ID: 1347028 • Letter: 1
Question
1. In an electrically heated home, the temperature of the ground in contact with a concrete basement wall is 14.5 °C. The temperature at the inside surface of the wall is 25.0 °C. The wall is 0.13 m thick and has an area of 8.5 m2. Assume that one kilowatt · hour of electrical energy costs $0.14. How many hours are required for one dollar's worth of energy to be conducted through the wall?
? h
2. The block in the drawing has dimensions L0 × 2L0 × 3L0, where L0 = 0.33 m. The block has a thermal conductivity of 251 J/(s·m·C°). In drawings A, B, and C, heat is conducted through the block in three different directions; in each case the temperature of the warmer surface is 33°C and that of the cooler surface is 17°C Determine the heat that flows in 4.8 s for each case.
(a) Q = ?
(b) Q = ?
(c) Q = ?
3. In a house the temperature at the surface of a window is 18° C. The temperature outside at the window surface is 11° C. Heat is lost through the window via conduction, and the heat lost per second has a certain value. The temperature outside begins to fall, while the conditions inside the house remain the same. As a result, the heat lost per second increases. What is the temperature at the outside window surface when the heat lost per second doubles?
? ° C
Explanation / Answer
1. In an electrically heated home, the temperature of the ground in contact with
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