##  [Fick's Second Law](/index.php/ficks-second-law) 

  ##  [Fick's Second Law](https://engineering.quantumdictionary.io/ficks-second-law-0) 

  

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**Engineering & Applied Technologies Dictionary**

 







 

 

 

 



 

 

 

 

Definition

For diffusion in a continuum with concentration‑dependent or constant diffusion coefficient D under isothermal conditions and negligible bulk motion, the time evolution of the local concentration c_i(r,t) obeys the diffusion equation derived from mass conservation and Fick’s first law: ∂c_i/∂t = ∇·(D·∇c_i). For constant D this reduces to ∂c_i/∂t = D·∇^2 c_i.