conduction v. convection v. radiation
Friday, September 17, 2010 Heat is transferred from high-temperature regions to low-temperature regions in a few fundamentally different ways: conduction, convection, and radiation.
Conduction
Conduction is the transfer of heat between substances that are in direct physical contact. When warm, fast-moving molecules collide with cooler neighboring molecules, some of their vibrational energy is transferred. You experience conduction when you touch a hot stove or an ice cube. Conduction is most effective in solids, particularly metals. Poor conductors (or insulators) include air, wood, and Styrofoam.
Convection
Convection is the bulk circulation of liquids or gases as hot, less dense material rises, and cool, denser material falls. Convection occurs in the oceans and the atmosphere, as well as within buildings and tea kettles. Conduction only involves molecular-scale particle motion, whereas convection involves the macroscopic movement of the entire medium.
Radiation
An infrared image of microwave burritos. Radiation is the transfer of thermal energy through space by electromagnetic waves. Radiative heating requires neither a medium nor the exchange of matter. Dull, black surfaces are better at absorbing thermal radiation than reflective white surfaces. The Sun heats the Earth by radiation. Microwave ovens, radiators, fires, and light bulbs transfer heat by both radiation and convection.