Physics

Why do aluminum pans heat food much more evenly than stainless steel pans when you cook on a stove?

Aluminum has a much higher thermal conductivity than stainless steel.

Why are good thermal conductors generally good electric conductors also?

Electron motion is responsible for determining both properties.

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?

It would increase

It's often a good idea to wrap food in aluminum foil before baking it near the red-hot heating element of an electric oven. Why does this wrapped food cook more evenly?

The aluminum foil conducts the heat evenly to all parts of the food.

Why do meats and vegetables cook much more quickly when there are metal skewers sticking through them?

The metal skewers conduct heat to the interior of the food.

Explain how convection contributes to the shape of a candle flame.

The rising warm air causes the flame to elongate upward.

Trace the transfer of energy that comes from your food.

The sun makes energy in the form of light. Plants then photosynthesize and store energy in their chemical bonds. People can eat the plants directly, breaking chemical bonds and utilizing the energy liberated.. Or, animals can eat the plants, breaking chemical bonds in the plants and re-storing the chemical potential energy in their bodies. Then humans consume the animals, utilizing the energy liberated from breaking the chemical bonds in the animal tissue. People can do work, or the energy can be used to heat the body, in which case it is radiated away and ultimately helps the universe expand.

The neighborhood children are playing and one has lost a pocketful of change. As a result they all decide to do a close inspection of the sidewalk. They notice that there are gaps in between the sidewalk filled with a felt - like material. These gaps will prevent

high stress due to thermal expansion

A pedestrian bridge crosses a street. This bridge is entirely supported by columns from below. A gap at each end of the bridge separates the bridge's surface from the sidewalks leading to the bridge. The width of each gap changes with time. This width is smallest

on hot days

People fighting forest fires carry emergency tents that have shiny aluminum outer surfaces. If there is trouble, a fire fighter can lie under the tent to block the heat from burning trees overhead. The tent helps because

radiation carries heat downward toward the fire fighter and the aluminum tent reflects most of that radiation.