Heat and Thermodynamics

4.10 Kinetic Theory of Conduction of Heat Through a Gas

In the simple calculation of heat conduction through a gas deduced from the transport theorem, it was assumed that out of the total number of molecules contained in a cubical box, one-sixth of the molecules move in a direction perpendicular to each face of the box. In the following deduction, we shall suppose that

1. the temperature of the gas increases in the direction of the z axis.
2. the mean energy of a molecule in any layer perpendicular to the z axis is that appropriate to the temperature of that layer.
3. the molecules moving in all possible directions have the same average velocity .

Let ...