P1b Keeping homes warm Flashcards
Why is trapped air in a material a very good insulator?
Trapped air in a material is a very good insulator because the air will not transfer energy to the another surface by conduction.
What is infrared radiation?
It is reflected from a shiny surface.
It is absorbed by a dull or rough surface.
How can the absorption and reflection of infrared radiation be applied in every day situations?
Infrared radiation can be used in cooking, remote controls-to transfer information to TVs and DVD players. They can also be used to transmit information between mobile phones or computers, however this can only be used over short distances. They are used in security systems an security lights because the sensors can detect heat from an intruder’s body. Infrared can also be used instead of visible light to carry information through optic fibres.
How is energy transferred?
CONDUCTION of heat is the process where vibrating particles pass on extra kinetic energy to neighbouring particles.
CONVECTION occurs when the more energetic particles move from the hotter region to the cooler region-and take their heat energy with then.
RADIATION occurs when infrared waves travel in straight lines at the speed of light-this is how heat is radiated.
How can losses in the homes be reduced by energy saving measures?
Loft insulation-fibreglass ‘wool’ laid across the loft floor reduces conduction through the ceiling into the roof place.
Double glazing-two layers of glass with an air gap between reduce conduction.
Cavity wall insulation-two layers of brick with a gap between then reduce conduction but you still get some energy lost by convection. Squirting insulating foam into the gap traps pockets of air to minimise this convection. (Heat is still lost through the walls by radiation though. Also, if there are any spaces where air is not trapped there’ll still be some convection too.)
How is energy transferred by conduction, convection and radiation?
Conduction-there is a transfer of kinetic energy between particles. In a solid, the particles are held together tightly
