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Thermal
Physics
Conduction
This is the way energy moves through
solids. Energy can be conducted through solids by two
mechanisms.
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i) |
Lattice vibrations.
When the nucleus of one atom vibrates, energy is
passed on to nearby nuclei |
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ii) |
The
motion of
free electrons.
This is the reason that metals are good
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The
rate of flow of energy
( Q/t)
through a solid depends on
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i) |
the temperature
difference (T)
causing the heat to flow |
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ii) |
the
length ( )
of the piece of solid |
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iii) |
the
cross-sectional area (A)
of the piece of solid |
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iv) |
the
material. |
Experiments show that
 Q/t
is
directly proportional
to
T
Q/t
is
directly proportional
to A
Q/t
is inversely
proportional
to
Combining these results gives
where k is a constant for a given material,
called the thermal
conductivity of the material. The quantity
T/
is called the temperature gradient.
The units of k are Wm-1°C-1.
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