In which law is the diffusion coefficient DAB used to relate flux to concentration gradient?

In which law is the diffusion coefficient DAB used to relate flux to concentration gradient?

• A. Fick's law
• B. Ohm's law
• C. Bernoulli's principle
• D. Boyle's law

Answer: (A)

Diffusion flux is described by Fick's law, which ties how much of a species moves through a medium to how its concentration changes in space using the diffusion coefficient D_AB. The law in vector form is J_A = -D_AB ∇C_A, meaning the flux of A is proportional to the negative gradient of its concentration. The negative sign indicates diffusion goes from higher to lower concentration, and the magnitude of D_AB reflects how easily A diffuses in B. In one dimension, this reduces to J_A = -D_AB dC_A/dx. This coefficient has units of area per time (m^2/s) and is a property of the A in B pair, capturing interactions and temperature effects that influence diffusion. This concept is central to modeling mass transfer in processes like filtration, membrane separation, or diffusion in porous media. The other options describe different phenomena: Ohm's law deals with electrical conduction, Bernoulli's principle with energy balance in flowing fluids, and Boyle's law with gas P-V behavior, none of which relate flux directly to a concentration gradient.

Diffusion flux is described by Fick's law, which ties how much of a species moves through a medium to how its concentration changes in space using the diffusion coefficient D_AB. The law in vector form is J_A = -D_AB ∇C_A, meaning the flux of A is proportional to the negative gradient of its concentration. The negative sign indicates diffusion goes from higher to lower concentration, and the magnitude of D_AB reflects how easily A diffuses in B. In one dimension, this reduces to J_A = -D_AB dC_A/dx. This coefficient has units of area per time (m^2/s) and is a property of the A in B pair, capturing interactions and temperature effects that influence diffusion. This concept is central to modeling mass transfer in processes like filtration, membrane separation, or diffusion in porous media. The other options describe different phenomena: Ohm's law deals with electrical conduction, Bernoulli's principle with energy balance in flowing fluids, and Boyle's law with gas P-V behavior, none of which relate flux directly to a concentration gradient.