HEAT CONDUCTION Conduction the transfer of heat by
HEAT
CONDUCTION • Conduction = the transfer of heat by the collision of particles in a solid • Heat conductor = a substance that conducts heat well (metal > paper) • Heat from flame = energy being added to the end of the metal rod • Metal particles closest to the source of heat/energy have more energy… → move more quickly → have more collisions → have weaker attractive forces → have more space between them → that part of the rod expands • Particles closest to heat source collide with neighbours and transfer their energy to them • Process continues down the metal rod → rod expands and feels warmer
RADIATION • So far heat transfer has occurred by convection (fluids) and conduction (solids) where both depend on the motion of particles • Radiation = the transfer of energy by means of waves (travelling across empty space) • Energy transferred by radiation = radiant energy ex) light ex) sun’s heat • Some objects absorb radiant energy better than others; some emit (give off) radiant energy better than others • Which object will absorb radiant energy fastest? • Which object will emit radiant energy fastest?
RADIATION • Dark colours tend to absorb radiant energy best • As the surface area increases, the energy absorbed also increases • Dark colours tend to emit radiation best • As the surface area increases, the energy emitted also increases • A good absorber is also a good emitter • Light and shiny colours are good reflectors of radiant energy
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