thermal physics: thermal processes

conduction

* transfer of heat through direct contact with another object
* metals = good conductors due to free moving electrons
* the atoms in a solid vibrate and bump into each other

insulators

- poor conductors
- materials w/ air pockets make very good insulators (bc gas is bad insulator)

examples of conductors

metal, marble

examples of insulators

glass, wood, rubber, air, plastic

experiment to demonstrate good and bad thermal conductors

- take metal rods of different materials
- attach a pin to each, using wax
- put rods into boiling water
- measure time taken for wax to fall off

convection

- method of energy transfer in fluids
- molecules push against each other, making liquid expand
- hot air or liquid is less dense than cold air or liquid
- hot air rises, cool air sinks
- starts a circulation (convection currents)

sea breezes

- day: land heats up quicker than water
- warm air rises over land and circulates back to land as a cool in-shore sea breeze
- night: land cools quick than water

radiation

- does not require a medium to travel through
- all hot objects give off thermal radiation
- hotter --\> more they emit

black

good absorber/emitter

dull/dark

reasonable absorber/emitter

white

poor absorber/emitter

shiny

very poor absorber/emitter

infrared radiation

part of the electromagnetic spectrum involved in energy transfer through radiation

factors affecting radiation

temp, color, surface area