# Current Density Formula

Current density refers to the density of current and denoted by the symbol J. In the field of electromagnetism, Current Density is the measure of flow of electric charge in amperes per unit area of cross-section (m²). This is a vector quantity, with both magnitude and direction. An electrical current flowing through and having units of charge per unit time per unit area are measured in the direction perpendicular to the flow of direction.

It concerns about the amount of current flowing across the given area.

Current Density Formula is expressed as,

J = I / A

Where,

I denotes the current flowing through the conductor in Amperes and

A denotes the cross section area in m2

Current density is expressed In A/m2

Example 1

A 5 mm2 copper wire has a current of 5 mA of current flowing through it. Determine the current density.

Solution

The Given parameters are

Total Current I is 5 mA

Total Area A is 5 mm2

The Current density  J = I / A

= 5×10−3 / 5×10−3

= 1 A/m2

Example 2

Determine the current density of 50 Amperes of current is flows through the battery in an area of 10 m2?

Solution

Given parameters

Current I is 50 A,

Area A is 10 m2

The current density is given by J = 50 / 10

= 5 A/m2.

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