March 25, 2009

1. Bellringer
2. IPC 6B Heat transfer notes

Conduction

•Transfer of heat by direct contact. Heat flows from the warmer object to the colder object.
•Solids are better conductors of heat than liquids or gases.
•Metals are good conductors.
•Wood, plastic, glass, and fiberglass are poor conductors of heat and are used as insulators.

Convection


•Transfer of heat in a fluid (liquid or gas) by the movement of heated particles.
•In a warm fluid, the more energetic molecules spread out, making the fluid expand and become less dense. The less dense fluid rises. The colder fluid sinks below the less dense fluid.
•This rising and sinking action is called a convection current.

Radiation


•Transfer of heat energy by electromagnetic waves.
•This is how the sun’s energy gets to earth. When you stand near a fire and warm yourself, most of the warmth you feel has been transferred by radiation.
•Light colored materials tend to reflect more radiant energy.
•Dark colored materials tend to absorb more energy.
•Radiation may travel through a vacuum (no matter is required).