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1.) Your body is presently converting chemical potential energy from food into thermal energy at a rate of about 100 J/s, or 100 W. If heat were flowing out of you at a rate of about 200 W, what would happen to your body temperature?

Answer: Your body temperature would drop since every second your body would LOSE 100 J of energy.

8.) When you heat a pot of water on the stove, the water's temperature is almost uniform throughout the pot. Why?

Answer:As the water is heated, convection cells are established that will carry the energy from the bottom(higher temperature) to the top (cooler since its further from the heat source). And if two adjacent "portions" of water are not at the same temperature, heat will flow from the hotter portion to the cooler by convection until their temperatures are equal.

10.) Most refrigerators use the freezing compartment to cool the refrigerating comparment as well. Why do most refrigerators place the freezing compartment on top?

Answer:Hot air is less dense and more energetic, so the warmer air in the refrigerator will be at the top. Colder air is denser and tends to sink, so in the freezer, the colder air is on the bottom. With the freezer on top, the colder air can absorb some of the heat from the warmer air in the refrigerator and the cold air will fall naturally owing to its higher density.

14.) Why are black steam radiators better at heating a room than radiators that have been painted white or silver?

Answer:Black surfaces are more efficient at emitting heat, in other words, their emissivity is higher than that of a white or silver surface.

17.) Mothballs are made from a white solid (naphthalene) that has a strong odor. If you leave a mothball out, it slowly disappears. What happens to the mothball?

Answer: The mothball sublimates, which is the fancy name for a solid undergoing a phase transition from the solid state to the gaseous state. Basically, there is NOT a puddle of mothball left over to tell you that its changing phase.

22.) You have a table lamp with a dimmer switch. The dimmer allows you to adjust the temperature and brightness of the lamp's incandescent bulb from very dim red up to brilliant yellow-white. How does the bulb's energy efficiency, the amount of visible light it produces per unit of power consumed, depend on the dimmer's setting?

Answer:If you dim the light bulb, the peak intensity will shift towards the red end of the spectrum so more energy is emitted as non-visible light. Also, the overall energy emitted will be less because of the reduction in temperature.

23.) When you operate a 50-100-150 W three-way bulb at its 50 W setting, it emits yellow-white light. When you use a dimmer too operate a regular 150 W bulb on only 50 W of electric power, it emits orangish light. Explain the difference.

Answer:The 50 watt bulb is running at higher temperature and thus higher efficieny ( at producing visible light) while the 150 W bulb, being cooler, isn't.

28.) If you were laying steel track for a railroad, what influence would thermal expansion have on your work?

Answer: Thermal expansion will have a HUGE role to play. The tracks are laid at some temperature and length. As the air warms (or cools), the track pieces will expand slightly (or contract) and can even occasionally buckle because of the huge stresses on the ties.

6.) A refrigerator is a heat pump that cools the contents of a food locker. Like an air conditioner, it has an evaporator, a condenser, and a compressor.

a.) Where is the evaporator located in a refrigerator?

Answer:The evaporator removes the warm air so it would be located in the food locker.

b.)Where is the condenser?

Answer It is ootside the refrigerator box where it can "discard" the heat removed from the refrigerator.

c.)What will happen to the food's temperature if you wrap the refrigerator's condenser and compressor in thermal insulation, so that they can't exchange heat with the room?

Answer:These parts are outside the unit so that the heat removed from inside will be ejected outside. If you thermally insulate these pieces, then that heat cannot escape and the refrigerator would not be able to operate efficiently.

d.) What will happen to the temperature of the room if you open the door to the refrigerator and let it run for a few hours?

Answer:When the door is left open, the refrigerator is given heat, so the refrigerator will have to do a lot of work to remove that heat from the food container. So the refrigerator will pump out all that heat back into the room. However, the refrigerator, due to mechanical efficiency, will produce extra heat in the process of doing the work needed to remove heat from the refrigerator. So the net result is that the room will warm up.

e.) Why does it take more electricity to operate a freezer than a refrigerator of similar size and quality?

Answer:They may be of the same size, but they perform different amounts of work. The freezer will extract MORE heat from it's contents which means it must do more work to move more heat from its innards.