Thermal Physics

Conduction

This is the way energy moves through solids. Energy can be conducted through solids by two mechanisms.

The rate of flow of energy (DQ/Dt) through a solid depends on

	i)	the temperature difference (DT) causing the heat to flow
	ii)	the length () of the piece of solid
	iii)	the cross-sectional area (A) of the piece of solid
	iv)	the material.

Experiments show that

DQ/Dt is directly proportional to DT

DQ/Dt is directly proportional to A

DQ/Dt 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 DT/ is called the temperature gradient.

The units of k are Wm^-1°C^-1.

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