DoITPoMS

back

Derivation of Fick's second law

Consider a cylinder of unit cross sectional area. We take two cross-sections, separated by δx, and note that the flux through the 1st section will not be the same as the flux through the second section.

Diagram of flux through 2 sections of cylinder

From Fick’s first law we can deduce that:

Equation

In an increment of time,δt, there is a corresponding increment in concentration, δC.

Equation

This is Fick’s second law


back