Solution 2

Chapter 6 Heat and Thermodynamics

Exercises  5,6,7,9,14,16,19,21,30,33,40
Problems 5

E5. Because the metal is a good conductor of heat and this conducts heat to the inside of the food.

E6. Because aluminum is a better conductor of heat then stainless steel.

E7. Because the convection can pull fresh air (and oxygen) from below the wood to help the fule burn.

E9. The convection cause the warm air/burning gas to rise causing the "flame" to go up not out in all directions.

E14. Because the black paint gives it the best emissivity. A better absorber(i.e. black) is also a better emitter.

E16. By thermal radiation to the surrounding outer space.

E19. By its color. The hotter the object the more the color tends towards shorter wavelengths (i.e. blue). so red hot is cooler orange, orange is cooler then white, white cooler then blue.

E21. Because 3K is so cold that the color (i.e. wavelength) is so long that it is in the microwave region of the spectrum, well below visible light.

E30. Because bridges change temperature with the weather, and when they change temperature they will expand and contract accordingly. These expansion gaps are there to allow this to happen without undo stress and damage to the bridge.

E33. It Increased. just like the adiabatic compression of the air in the demo. conservation of energy causes this. the work done on compressing the gas is converted to thermal energy (i.e higher temperature)

E40. The overall entropy of the system must always increase. In this case it increases by heat flowing from hot to cold.

P5. The heat radiated away is proportional to the surface area of the emitter. If the emitter area is doubled twice the heat will be radiated away.