Heat Transfer9 Flashcards
Anything that is hot…
Gives out infrared radiation
A thermal image…
Is a picture made using infrared radiation
Infrared radiation can travel through…
Space (a vacuum) and transparent material like glass
Heat radiation is also called…
Infra red radiation
All objects…and…infra-red radiation.
Absorb
Emit
The …an object is, the …infrared radiation it emits in a given time.
Hotter
More
Cold objects?
Absorb heat radiation
Hot objects?
Emit heat radiation
Light/shiny objects?
Reflect heat well but doesn’t absorb heat well do not heat up much, emits heat slowly stay hotter for longer
Dark/dull objects?
Absorb more heat this means they heat up quickly. Hot dark objects also emit heat radiation very well this means that they cool down quickly.
How does heat travel through a solid?
By a process called conduction, caused by particles vibrating and knocking into each other.
Why are metals good conductors?
Because they contain “free electrons” which can move around the whole metal and carry the heat energy through more easily.
Why are non-metals bad conductors?
They don’t contain free electrons.
Are liquids and gases good conductors of heat?
Liquids and gases are bad conductors because the particles are too far apart to knock into each other.
Why does a metal cup feel colder than a polystyrene cup?
The metal cup will conduct heat away from your hand.
Heat travels through liquids and gases by a process called?
Convection
Convection involves hot particles…and cooler particles…in a continuous cycle called a… …
Rising
Falling
Convection currents
The cycle continues until the whole liquid or gas becomes the same…
Temperature
Heat can be lost from buildings by conduction through the…
Roof, floor, window glass, walls
Heat can be lost from buildings by convection through the…
Draught
How can you save heat?
Insulating, double glazing, fitting draught excluders
Materials used for insulating often contain… Because
Air
A gas such as air is a very poor conductor
Why is a foam container a better insulator than a metal?
- foam container is a better insulator
- prevents heat getting in
What are the three ways that heat can be transferred?
Radiation, convection, conduction
How is a fibre sleeping bag designed to reduced heat transfer by which 2 processes?
- Conduction
- Convection
Why is a fibre sleeping bag good at reducing heat loss?
- there is air space between the fibre and air isn’t a good conductor
- the air is trapped in the fibre so it can’t convect either
