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How is current density calculated from electric current and cross-sectional area?

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density current: descent to the ocean floor — density current Diagram showing the behaviour of a density current as it descends to the seafloor.

The term "density current" typically refers to a fluid dynamics phenomenon involving the flow of one fluid through another of different density; it is distinct from the concept of electric current density used in physics and electromagnetism.

In the context of electric current, current density—symbolized by J—is defined as the flow of current per unit area of a cross section perpendicular to the direction of flow. It is calculated using the following formula:12

$J = \frac{i}{A}$

In this equation:
* J is the current density, measured in amperes per square metre (A/m²).2
* i is the electric current, measured in amperes (A).2
* A is the cross-sectional area through which the current flows, measured in square metres (m²).2

This relationship is fundamental to understanding how electric fields and material properties, such as conductivity, influence the movement of charge carriers within a conductor.2