Chapter 15 Heat Transfer

Front 1

Conduction

Back 1

the transfer of heat energy by molecular and electron collisions within a substance (especially a solid)

Front 2

Convection

Back 2

the transfer of heat energy in a gas or liquid by means of currents in the heated fluid. The fluid moves carrying energy with it.

Front 3

Radiation

Back 3

The transfer of energy at the same speed of light by means of electromagnetic waves

Front 4

Newton's law of cooling

Back 4

The rate of loss of heat from an object is proportional to the temperature difference between the object and its surroundings

Front 5

greenhouse effect

Back 5

The heating effect of a medium such as glass or the earth's atmosphere that is transparent to the short- wavelength radiation of sunlight but opaque to long wavelength terrestrial radiation. Energy of sunlight that enters teh glass of a florist's greenhouse or teh atmosphere of the earth is absorbed and reradiated at a longer wavelength that is consequently trapped, producing heating.

Front 6

Solar constant

Back 6

1400 J/m^2 received from teh sun each second at the top of the earth's atmosphere on an area perpendicular to the sun's rays; expressed in terms of power, 1.4 kW/m^2

Front 7

Solar Power

Back 7

energy per unit time derived from the sun.

Front 8

What is the role of "loose" electrons in heat conductors?

Back 8

Solids whose molecules have one or more "loose" outer electrons conduct heat (an electricity) well. Metals have the "loosest" outer electrons and are the best conduyctors of heat and electricity for this reason.

Front 9

Distinguish between a conductor and an insulator.

Back 9

wool, wood, straw, paper, cork, and Styrofoam are poor conductors of heat. The outer electrons in the molecules of these materials are firmly attached. Poor conductors are called insulators.

Front 10

Why does a room-temperature tile feel cooler to the bare feet than a wooden floor?

Back 10

The tile floor feels colder than wooden even though they are the same temperature. This is because tile is a better conductor than wood and heat is mroe readily conducted from teh foot that makes contact with the tile.

Front 11

Why do we say that cold is not a tangible thing?

Back 11

Heat is transmitted from a higher to a lower temperature. We often hear people saw they wish to keep the cold out of their homes. A better way to put this is to say that they want to prevent the heat from escaping. There is no "cold" that flows out into a warm home. If the home becomes colder, it is because heat flows out. Homes are insulated with rock

Front 12

Convection
How is heat transferred from one place to another by convection?

Back 12

Liquids and gases transmit heat mainly by convection, which is heat transfer by the actual motion of the fluid- by currents.

Front 13

Why Fast moving molecules rise in air
How does buoyancy relate to convection?

Back 13

A fast moving molecule tends to migrate toward the region of least obstruction upward. Warm air expands, becomes less dense than the surrounding air, and is buoyed upward like a balloon.

Front 14

Radiation
What exactly is radiant energy?

Back 14

Heat is transmitted through the atmosphere not by conduction because air is a poor conductor, nor by convection for convection begins only after the earth is warmed, but in another way called radiation, It is in the form of electromagnetic waves

Front 15

How do the wavelengths of radiant energy vary with the temperature of the radiating source?

Back 15

Objects at a low temperatures emit long waves, just as long lazy waves are produced when you shake a rope with little energy. Higher- temperature objects emit waves of shorter wavelengths.

Front 16

If you want a room-temperature can of beverage to cool quickly, should you put it in the freezer compartment or in the main part of your refrigerator? Or does it not matter?

Back 16

A relatively hot object cools as it warms its surroundings; a cool object warms as it cools its surroundings. The rate of cooling of an object depends on how much hotter the object is than the surroundings. The temperature chage per minute of a hot apple pie will be more if the hot pie is put in a cold freezer than if put on a kitchen table. likewise. If you keep the temperature difference small the rate of cooling will be correspondingly low, so put the can in the freezer!

Front 17

Which will undergo the greater rate of cooling, a red-hot poker in warm oven or a red-hot poker in a cold room ( or do both cool at the same rate)?

Back 17

In newton's law of cooling holds that if an object is cooler than its surroundings, its rate of warming up is also proportional to the change in temperature. So a red hot poker in a cold room

Front 18

Does Newton's laws of cooling apply to warming as well as cooling?

Back 18

yes

Front 19

What is mean by terrestrial radiation?

Back 19

The earth emits terrestrial radiation which goes out into oute space.

Front 20

Why is radiant energy from the sun composed of short waves and terrestrial radiation composed of relatively longer waves?

Back 20

Hot sources emit short waves, while cooler sources emit longer waves.