Day 9 5.3.11

Topic: Finish Convection, Begin Radiation

Obj: I can describe a draw a convection current

Starter: Explain how a

radiator can heat a room.

Natural convectionFluids expand when they heat up. In a container (or

environment), warmer fluid floats to the top and cooler fluid sinks to the bottom. This is called natural convection.

Forced convectionIn many houses a furnace heats air and then circulates

the air to rooms. Since the heat is being forced through the system (with blowers) and circulating with other air, this is another example of convection. However, since the air is forced to flow by the blowers or fans, this is called forced convection.

Convection (thru fluid) typesForced

Fan behind heat source

Heat Source

Forced

Eureka

•Convection 27or

•Conduction 24

Natural Convection Current Demo:“Shoe Box

House”

1st Floor

2nd Floor

Sketch Either image

Cool Air

Warm Air

Conclusion:As warm air rises and exits the house, cool air replaces the warm air which continues the convection current

Ball & Ring Demonstration

Thermal Radiation

• All objects with a temperature above absolute zero (-273 °C or -459 °F) emit thermal radiation. To emit means to give off.

• Thermal radiation comes from the thermal energy of atoms.

• Thermal radiation is also absorbed by objects. An object constantly receives thermal radiation, otherwise all objects would eventually cool down to absolute zero.

Three identical aluminum bottles were spray painted and set in the window.Predict the temperature of the fluid inside of each bottle using the oC.Justify your response.

Eureka 29

ThermalRadiation

Radiation: heat transfer in the form of electromagnetic waves, including light.

Sketch this image.

Reflects MOST Radiation Absorbs MOST Radiation &Emits as Heat Energy

Thermal Radiation

Colors

• Black asphalt pavement gets very hot in the summer sun because it effectively absorbs thermal radiation. A silver mirror surface reflects most thermal radiation, while absorbing very little.

Solar Radiation• Radiant Energy travels on waves through space on

particles or pure energy. Radiation is a heating mechanism

that takes place through electromagnetic waves.