Conduction
Conduction is the transfer
of heat energy through solids or stationary fluids. Heat
is transferred by lattice vibrations and particle collisions.
In solids atoms are bound together
by bonds which behave like springs. Atoms that are hot
will vibrate more vigorously with these vibrations, and therefore
energy, being transferred to neighbouring atoms until equilibrium
is reached (i.e. until all the atoms have the same energy/temperature).
Energy is also transferred
by particle collisions. Hotter molecules move faster than
cooler ones, and energy is transferred to the lower energy
molecules when they collide. These random collisions continue
until equilibrium is reached, when the molecules are moving with
the same average velocity. This behaviour is seen in stationary
fluids and with the free electrons in metals.
The rate of heat transfer due to conduction
is:
Where:
It is clear from the above equations that there will be lower heat
flow (higher resistance) if the thermal conductivity is lower, the heat
path is longer, or the area is lower.
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