P2 Energy Transfer By Heating Flashcards
What type of surface do the best emitters of infrared radiation have?
Black matt surfaces
What type of surface do the worst emitters of infrared radiation have?
Light shiny metallic surfaces
What type of surface do the worst absorbers of infrared radiation have?
Light shiny metallic surfaces
They tend to reflect the radiation
What type of surface do the best absorbers of infrared radiation have?
Black matt surfaces
Explain why an object’s temperature decreases with regard to infrared radiation
The object emits more infrared radiation than it’s absorbing
e.g. a hot cup of tea cooling down
Explain why an object’s temperature increases with regard to infrared radiation
The object absorbs more infrared radiation than it’s emitting
e.g. an ice cube warming up and melting
Explain why an object’s temperature stays constant with regard to infrared radiation
The object absorbs infrared radiation at the same rate it emits it
What is meant by an objects “Thermal Conductivity”?
How well an object transfers energy via conduction
What are the three processes of heating, and what states of matter do they apply to?
Conduction - Solids
Convection - Fluids
Radiation - Vacuums (empty space)
Give examples of objects with high and low thermal conductivities
High - Solids
Low - Plastics and all fluids
Why are plastics good insulators?
They have a low thermal conductivity
Describe ways to increase an objects rate of energy transfer
- Increase it’s thermal conductivity
- Decrease it’s diameter/thickness
- Decrease it’s temperature difference across the object
What is a “Perfect black body”?
An object that absorbs all the radiation that hits it
What is the relation between an objects ability to absorb and emit radiation?
A good absorber will be a good emitter
and vice versa
Why can convection and conduction not occur in vacuums?
They require particles to transfer heat energy
