# Shared Flashcard Set

## Details

energy
revision aqa
21
Physics
06/03/2011

Term
 Thermal radiation is energy transfer by            waves.
Definition
 electromagnetic waves
Term
 Dark, matt surfaces are good           of thermal radiation.
Definition
 absorbers / emitters
Term
 Light, shiny surfaces are good            of infrared radiation.
Definition
 reflectors
Term
 A thin, flat object will radiate heat energy              than a fat object.
Definition
 faster
Term
 Describe the particles in a solid.
Definition
 The particles in a solid are held next to each other in fixed positions . They vibrate about their fixed positions so the solid keeps its own shape.
Term
 Describe the particles in a liquid.
Definition
 The particles in a liquid are in contact with each other.  They move about at random. So a liquid doesn’t have its own shape and can flow.
Term
 Describe the particles in a gas.
Definition
 The particles in a gas move about at random much faster. So There are on average , much further apart from each other than in a liquid. So the density of a gas is much less than that of a solid.
Term
 What is conduction?
Definition
 The transfer of heat energy through a substance.
Term
 What are poor conductors of heat called?
Definition
 Insulators
Term
 When does convection occur?
Definition
 Convection occurs when particles with a lot of heat energy in a liquid or gas move and take the place of particles with less heat energy.
Term
 What states of matter can convection happen in?
Definition
 Liquids and gases
Term
 In convection why does the liquid or gas in hotter areas rise to cooler areas?
Definition
 It becomes less dense.
Term
 Evaporation
Definition
 Evaporation is when a liquid turns into a gas.
Term
 Condensation
Definition
 Condensation is when a gas turns into a liquid.
Term
 Evaporation can be increased by:
Definition
 increasing the surface area of a liquid, increasing the liquids temperature, by creating a draught of air across the liquids surface.
Term
 Condensation on a surface can be increased by
Definition
 increasing the area of surface , reducing the temperature of the surface.
Term
 the rate at which an object transfers energy depends on its design.  The design factors that matter are:
Definition
 the materials the object is in contact with  the object’s shape the objects surface area
Term
 What do U-valves tell us?
Definition
 U-valves tell us how much heat per second passes through different materials.
Term
 Energy loss from our homes can be helped by fitting:
Definition
 loft insulation cavity wall insulation double glazing draught proofing aluminium foil behind radiators.
Term
 Power (in watts) =
Definition
 energy transferred (in joules)   time taken (in seconds)
Term
 Efficiency =
Definition
 useful power out     x 100   total power in
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