- Heat is transferred by conduction when particles in the heated region vibrate more rapidly and transfers energy to cooler regions.
- Metal is a good conductor of heat because free electrons can rapidly transfer heat energy to cooler areas.
- Non-metals and gases are poor conductors of heat (good heat insulators).
- Convection is caused by the bulk movement of fluids (liquid and gas).
- When fluid is heated, it expands and becomes less dense. Warmer fluid rises, which is replaced by cooler and denser fluid moving downwards.The warmer fluid will eventually cool down after it rises and move downwards again. This causes a convection current.
- All materials emit and absorb heat in a form of infrared radiation.
- Hotter objects emit more radiation.
- If the temperature of the material is higher than the surrounding, it will emit more radiation that it absorbs radiation. If the temperature of the material is lower than the surrounding, it will absorb more radiation than it emits radiation.
- Dark and rough surfaces are good emitters and absorbers of radiation. Light and shiny surfaces are poor emitters and absorbers of radiation.
- Light and shiny surfaces are good reflectors of radiation.
IV. Minimizing Heat Loss in Houses
- Strips of foam around door frames of thick curtains: reduce heat loss by convection. Warm air inside the house can move to colder parts of the house rather than exiting the house through doors or windows.
- Double glazing of glass windows: reduce heat loss by conduction. Air is trapped between two glass panes, and air is a good heat insulator.
- Cavity wall insulation: reduce heat loss by conduction and convection. Insulating foam is injected between inner wall and outer wall.
- Loft insulation: reduce heat loss by conduction and convection. Cover the loft floor with wooly material, which traps air and is a good insulator.
- Reflective foil: reduce heat loss by radiation. When reflective foil is fitted on walls or curtains, radiation from the house will be reflected back in to the house.