The thermal conductivity of aluminum is 238 JsmC and of copper is 397 JsmC A

# The thermal conductivity of aluminum is 238 jsmc and

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60. The thermal conductivity of aluminum is 238 J/s·m·°C and of copper is 397 J/s·m·°C.A rodof each material is used as a heat conductor. If the rods have the same geometry and are usedbetween the same temperature differences for the same time interval, what is the ratio of theheat transferred by the aluminum to the heat transferred by the copper? a. 0.599b. 1.67c. 0.359d. 2.78A 61. I place a 500-g ice cube (initially at 0°C) in a Styrofoam box with wall thickness 1.0 cm andtotal surface area 600 cm2. If the air surrounding the box is at 20°C and after 4 hours the ice iscompletely melted, what is the conductivity of the Styrofoam material? (Lf = 80 cal/g) 62. Consider two different rods. The greatest thermal conductivity will be in the rod with: 63. Which type of heating causes sunburn? 64. In winter, light-colored clothes will keep you warmer than dark-colored clothes if: a. you are warmer than your surroundings.b. you are at the same temperature as your surroundings.c. you are cooler than your surroundings.d. you are standing in sunlight.A 65. A silver bar of length 30 cm and cross-sectional area 1.0 cm2is used to transfer heat from a100°C reservoir to a 0°C block of ice. How much ice is melted per second? (For silver, k=427 J/sm°C. For ice, Lf = 334 000 J/kg.) 66. At high noon, the sun delivers 1 000 W to each square meter of a blacktop road. What is theequilibrium temperature of the hot asphalt, assuming its emissivity e = 1? (σ = 5.67 × 10−8W/m2K4) . 67. The surface of the Sun has a temperature of about 5 800 K. If the radius of the Sun is 7 × 108m, determine the power output of the sun. (Take e = 1, and σ = 5.67 × 10−8W/m2K4). 68. The tungsten filament of a light bulb has an operating temperature of about 2 100 K.If theemitting area of the filament is 1.0 cm2 , and its emissivity is 0.68, what is the power output ofthe light bulb? (σ = 5.67 × 10−8W/m2K4) a. 100 Wb. 75 Wc. 60 Wd. 40 WB 69. An object at 27°C has its temperature increased to 37°C. The power then radiated by thisobject increases by how many percent?  #### You've reached the end of your free preview.

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