Conduction, Convection and Radiation Flashcards
What is heat?
Heat is thermal energy.
How can heat be transferred from one place to another?
Heat can be transferred from one place to another by convection and conduction.
How can energy be transferred?
Energy can be transferred by conduction, convection, and radiation.
What is insulation used to stop?
Insulation is used to stop heat energy transfer from buildings and the human body.
Why are liquids and gases ‘fluids’?
They can be made to flow. The particles in these fluids can move from place to place.
When does convection occur?
When particles with lots of heat energy in a liquid or gas move and take the place of particles with less heat energy.
What happens to liquids and gases when they are heated?
They expand.
Why do liquids and gases expand when heated?
The particles in liquids and gases move faster when they are heated than they do when they are cold.
How can heat be transferred?
Infrared radiation.
What type of radiation is infrared radiation?
Unlike conduction and convection - which need particles - infrared radiation is a type of electromagnetic radiation that involves waves.
Why can radiation work through the vacuum of space?
No particles are involved. This is why we can still feel the heat of the sun even though it’s 150 million km away from the earth.
What surfaces are good absorbers and emitters of infrared radiation?
Dull, matt or rough surfaces.
What surfaces are poor absorbers and emitters of infrared radiation?
Shiny surfaces. However, they are good reflectors of infrared radiation.
Why are domestic radiators thin and flat?
If two objects made from the same material have identical volumes, a thin, flat object will radiate heat energy faster than a fat object.
How do radiators transfer most of their heat?
Despite their name, radiators actually transfer most of their heat energy to a room by convection, not radiation.
How is heat energy transferred from homes?
By conduction through the walls, floor, roof and windows. It is also transferred from homes by convection.
How does heat energy leave the house?
By radiation - through the walls, roof, and windows
List four ways to reduce heat loss:
- Fitting carpets, curtains,and draught excluders. It is even possible to fit reflective foil in the walls or on them.
- Heat loss through windows can be reduced by using double glazing. These special windows have air or a vacuum between two panes of glass
- Heat loss through walls can be reduced using cavity wall insulation. This involves blowing insulating material into the gap between the brick and the inside wall.
- Heat loss through the roof can be reduced by laying loft insulation. This works in a similar way to cavity wall insulation.
What does conduction and convection involve?
Conduction and convection involve the transfer of energy by particles.
What is the main form of heat transfer in solids?
Conduction
What is the main form of heat transfer in liquids and gases?
Convection
What can infrared radiation be emitted by?
Solids, liquids and gases.
Can any object absorb and emit infrared radiation?
Yes, any object can both absorb and emit infrared radiation, whether or not conduction or convection are also taking place.
What is infrared radiation emitted from?
The surface of an object. All objects are continually emitting and absorbing infrared radiation.
