Fick's Law of Diffusion Fick's law of diffusion is a mathematical relationship that describes the relationship between the concentration gradient, the diffu...
Fick's Law of Diffusion
Fick's law of diffusion is a mathematical relationship that describes the relationship between the concentration gradient, the diffusion coefficient, and the distance of a substance from a source or sink. It is a fundamental principle in heat transfer, describing the diffusion of a substance away from an area of higher concentration to an area of lower concentration.
The law states that the flux of a substance from a source to a sink is proportional to the concentration gradient and inversely proportional to the square root of the distance from the source. It can be expressed mathematically as follows:
J = -D * (ΔC/Δx)^(1/2)
Where:
J is the flux of the substance
D is the diffusion coefficient
ΔC is the concentration difference between the source and sink
Δx is the distance from the source
The negative sign indicates that the flux is inward, from the source to the sink.
Interpretation
The law tells us that the flux of a substance towards a sink increases as the concentration difference between the source and sink increases, and decreases as the distance from the source increases. It also tells us that the flux of a substance towards a sink is inversely proportional to the square root of the distance from the source. This means that the flux is faster for substances that are closer to the source, and slower for substances that are farther away.
Examples
The law can be used to explain the diffusion of heat into a room. The heat flux will be higher near the surface of the room, and lower further away.
It can also be used to explain the diffusion of pollutants in a pollutant-laden air. The pollutants will accumulate closer to the ground, and less so further up.
The law can also be used to explain the diffusion of a drug in the body. The drug will diffuse more quickly through fat tissue, than it will through muscle tissue