How Do Conduction, Convection, and Radiation transfer heat




Ethan W 2011

Conduction.jpg
This represents Conduction, because of the clashing temperatures



Conduction

Conduction occurs when two objects at different temperatures are in contact with each other. Heat flows from the warmer to the cooler object until they are both at the same temperature. Conduction is the movement of heat through a substance by the collision of 2 different objects at different temperatures. At the place where the two object touch, the faster-moving molecules of the warmer object collide with the slower moving molecules of the cooler object. As they collide, the faster molecules give up some of their energy to the slower molecules. The slower molecules gain more thermal energy and collide with other molecules in the cooler object. Thermal energy is generated and measured by heat of any kind. It is caused by the increased activity or speed of molecules in a substance, which in turn causes temperature to rise accordingly. This process continues until heat energy from the warmer object spreads throughout the cooler object. Some substances conduct heat more easily than others. Solids are better conductor than liquids and liquids are better conductor than gases. Metals are very good conductors of heat, while air is very poor conductor of heat. You experience heat transfer by conduction whenever you touch something that is hotter or colder than your skin.
Examples of good conductors: Metal, Wax, Additionally, some liquids are very useful for carrying heat because they can flow or can carry heat by either vaporization/condensation or by melting/solidifying (like cooling you drink with ice). Examles: Water, sodium, mercury, and alcohol.

Convection

In liquids and gases, convection is usually the easiest way to transfer heat. Convection occurs when warmer areas of a liquid or gas rise to cooler areas in the liquid or gas. As this happens, cooler liquid or gas takes the place of the warmer areas which have risen higher. This cycle results in a continuous circulation pattern and heat is transferred to cooler areas. You see convection when you boil water in a pan. The bubbles of water that rise are the hotter parts of the water rising to the cooler area of water at the top of the pan. This is a description of convection in our atmosphere. Heat energy is transferred by the circulation of the air. Convection currents can cause clouds to form. Warm air, heated by the land, can hold more Water Vapor then cold air can. Convection makes the warm air rise then the water cycle happens.
Convection.jpg
This is different temperature in gases

Radiation.png
The Radio tower sends signals to the microwave tower which heats up the fire through the air
Radiation

Both conduction and convection require matter to transfer heat. Radiation is a method of heat transfer that does not rely upon any contact between the heat source and the heated object. For example, we feel heat from the sun even though we are not touching it. Heat can be transmitted though empty space by thermal radiation. Radiation is a form of energy transport consisting of electromagnetic waves traveling at the speed of light. No mass is exchanged and no medium is required.
Objects produce radiation when high energy electrons in a higher atomic level fall down to lower energy levels. The energy lost is produced as light or electromagnetic radiation. Energy that is absorbed by an atom causes its electrons to "jump" up to higher energy levels. All objects absorb and produce radiation. When the absorption of energy balances the emission of energy, the temperature of an object stays constant. If the absorption of energy is greater than the emission of energy, the temperature of an object rises. If the absorption of energy is less than the emission of energy, the temperature of an object falls.


Fun Games on Heat Transfer
Glossary
Molecules: Any small Particle
Electromagnetic: of, containing or operated by an electromagnet

Substance:that of which a thing consists;physical matter or material:


Citations
"heat." Compton's by Britannica. Encyclopedia Britannica Online School Edition.

Encyclopædia Britannica, Inc., 2011. Web. 23 Sept. 2011.

<http://school.eb.com/all/comptons/article-201969>.

Cooke, Tom. Facts at Your Fingertips Introducing Physics. Tucson, AZ: Brown Bear Books, 2010. Print.

“Electromagnetic Origin.” http://dictionary.reference.com/browse/Electromagnetic. Collins English Dictionary. September 7, 2009. Web. September 25, 2011.