Presentation on theme: "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."— Presentation transcript:
Day Topic: Finish Convection, Begin Radiation Obj: I can describe a draw a convection current Starter: Explain how a radiator can heat a room.
Natural convection Fluids 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 convection In 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) types Forced Fan behind heat source Heat Source Forced
Eureka Convection 27 or Conduction 24
Convection (thru fluid/air) Land BreezeORSea BreezeDAYEVENING
Natural Convection Current Demo: “Shoe Box House” 1 st Floor 2 nd 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 o C. Justify your response.
Eureka 29 Thermal Radiation
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.