# Current Density

## Definition - What does Current Density mean?

Current density or electric current density is related to electromagnetism and is defined as the amount of electric current flowing through a unit cross-sectional area. It is a vector quantity. The SI unit of electric current density is ampere per square meter. The symbol "J" is used for electric current density.

## Corrosionpedia explains Current Density

Current density can be expressed by the formula:

J = I / A

where:

J = Electric current density in amperes per sq. meter.

I = Electric current flowing through a given material or a conductor in amperes.

A = Cross-sectional area of a material or a conductor in square meters.

As an example, let us find the current density through a copper wire having a cross-sectional area of 4 square millimeters through which a 6 mA current is flowing. Using the formula J = I/A

Current I = 6 mA = 0.006 A

Area A = 4 sq. mm = 0.004 sq. m

J = I/A = 0.006 Amp / 0.004 sq. m = 1.5 Amp/sq. meter