physics-thermal energy

conduction

movement of heat through a substance by the collision of particles

convection

when warmer fluids rise up through cooler fluids because they are less dense then surroundings,particles move position

radiation

all warm objects emit and absorb infared rays

black body?

A theoretical object that absorbs 100% of radiation and a perfect emitter,perfect absorber of electromagnetic radiation

U-value?

the rate of energy being passed through a square meter of structure. (lower u value the better as you want the heat to be trapped in your house and not escape)

how to find payback time

initial installation cost/annual savings on the bill

definition of payback time

the exact time it takes for an energy saving product to save more money than it originally cost

high thermal conductivity

can conduct heat very well like metals as they allow energy to transfer through it quickly e.g aerogel

low thermal conductivity

bad conductors of heat,wont let energy pass through it quickly e.g foam and wood

intensity

how much energy is given out per second over an area

Thermal energy

is always transmitted from hot areas to cool areas

thermal equilibrium

when two objects reach the same tempand theres no longer a net transfer of thermal energy

why can an object stay at a constant temp

if the rate of infrared radiation it absorbs is the same as the rate of infrared emitted which is also the equilibrium state

insulator

materials that are poor conductors of heat and blocks the flow of electrical and thermal currents

good insulators ?

fiberglass,aerogel,

bad insulators ?

brick, wood