Exam 13: The Transfer of Heat

A granite wall has a thickness of 0.50 m and a thermal conductivity of 2.1 W/(m·C°).The temperature on one face of the wall is 5.2 °C and 20.0 °C on the opposite face.How much heat is transferred in one hour through each square meter of the granite wall?

Two kilograms of ice at 0.0 °C are placed in a sealed glass container [k = 0.80 W/(m · C°)].The container is then placed in a room that is maintained at 30.0 °C.The top cover is a thermal insulator and all other sides of the container are exposed to room air.The surface area of the container is 6.53 × 10^-² m²;and its glass walls are 0.0050 m thick. -Approximately,how long does it take all of the ice to melt?

In an experiment to determine the thermal conductivity of a bar of a new alloy,one end of the bar is maintained at 0.0 °C and the other end at 100.0 °C.The bar has a cross-sectional area of 1.0 cm² and a length of 15 cm.If the rate of heat conduction through the bar is 34 W,what is the thermal conductivity of the bar?

The power radiated by a distant star is 6.2 × 10²⁷ W.The radius of the star,which may be considered a perfect radiator,is 1.06 × 10¹⁰ m.Determine the surface temperature of the star.

The ends of a cylindrical steel rod are maintained at two different temperatures.The rod conducts heat from one end to the other at a rate of 10 cal/s.At what rate would a steel rod twice as long and twice the diameter conduct heat between the same two temperatures?

Two cylindrical steel rods A and B have radii of 0.02 m and 0.04 m,respectively.The two steel rods conduct the same amount of heat per unit time for the same temperature differences between their two ends.What is the ratio of the lengths of the rods,L_A/L_B?

Which one of the following objects,all initially at the same temperature,will be most efficient in losing heat?

Which one of the following statements best explains why convection does not occur in solids?

A beaker of water is placed on a Bunsen burner.As the lower layers of water are heated,they become less dense and rise.This permits cooler layers to move downward and be heated.Eventually,the water boils.Which method(s)of heat transfer is (are)primarily responsible for boiling the sample?

At what rate is heat lost through a 1.5 m × 3.0 m rectangular glass windowpane that is 0.4 cm thick when the inside temperature is 22 °C and the outside temperature is 6.0 °C? The thermal conductivity for the glass is 0.75 W/(m · C°).

A cabin has a 0.159-m thick wooden floor [k = 0.141 W/(m·C°)] with an area of 13.4 m².A roaring fire keeps the interior of the cabin at a comfortable 18.0 °C while the air temperature in the crawl space below the cabin is -16.4 °C.What is the rate of heatconduction through the wooden floor?

Assuming a filament in a 100 W light bulb acts like a perfect blackbody,what is the temperature of the hottest portion of the filament if it has a surface area of 6.3 × 10^-⁵ m²? The Stefan-Boltzmann constant is 5.67 × 10^-⁸ W/(m² · K²).

The sun continuously radiates energy into space in all directions.Some of the sun's energy is intercepted by the earth.The average temperature of the surface of the earth remains a little above 300 K.Why doesn't the earth's temperature rise as it intercepts the sun's energy?

Two bars,A and B,each of length 2.0 m and cross sectional area 1.0 m²,are placed end to end as shown in the figure. The thermal conductivities of the bars are k_A = 439 J/(s × m × K)and k_B = 887 J/(s × m × K),respectively.The left end of bar A is maintained at 373 K while the right end of B is maintained at 273 K. -Which one of the following statements is true concerning the above situation?

Two kilograms of ice at 0.0 °C are placed in a sealed glass container [k = 0.80 W/(m · C°)].The container is then placed in a room that is maintained at 30.0 °C.The top cover is a thermal insulator and all other sides of the container are exposed to room air.The surface area of the container is 6.53 × 10^-² m²;and its glass walls are 0.0050 m thick. -How much heat is required to melt the ice?

Complete the following statement: Most of the heat that is lost to space from the earth occurs by

Which one of the following statements concerning emissivity is false?

Object A has an emissivity of 0.95;and its temperature is 25 °C.At what temperature (in degrees Celsius)does object B,whose emissivity is 0.50,emit radiation at the same rate as object A if both objects have the same surface area?

If a beaker of water is placed under a broiler so that the heating coil is above the beaker.It is observed that only the surface layer boils.The water at the bottom of the beaker remains close to the initial temperature of the water.Which of the following statements is the most reasonable conclusion to be drawn from these observations?

Which of the following materials is the poorest thermal conductor?