Current Density Formula

Current Density Formula

The article below discusses the current, types of Current – AC, and DC, the current density formula, its unit, and examples.

• Current 

Current is a term used to define the flow of electrons from an electrically charged source to an electron-deficient region. The symbol I represents the current, and A-Ampere represents the SI unit of Current.

• Types of Current

Current is classified into two types: direct Current and Alternating Current.

Direct Current: Current which travels in a linear direction. It has only magnitude. The Direct Current has zero frequency. Example: Electrochemical cell

Alternative Current: Current which travels in the opposite direction. It differs in both magnitude and direction. They have a varying frequency above zero—for example, Radio signals.

• Current Density 

Current density is the amount of unit charge that passes through a unit area at a particular cross-section. It is a vector quantity. The electric current per unit cross-sectional area is positive when it flows in the same direction. The SI unit of electric current is the ampere, whereas it is the ampere per square meter for current density.

• Current Density Formula

Current density J = I / A

Whereas,

I = current passes through the conductor in ampere 

A = cross-sectional area in square meter.

Current density is expressed in A/m²

Example 1

Determine the current density of a battery when 40-ampere Current passes through an area of 10 m²

Solution:

Current I = 40 A

Area A = 10 m²

Current density formula J = I/A

= 40/10

J = 4 ampere/ m²

The current density J = 4 ampere/ m²

Example 2

Using the current density formula, determine the current density of a copper wire using the current density formula when 10 x 10^-3m² conducts an electric flow of 2mA.

Solution 

Current density = I/A

Current I = 2 x 10^-3

A = 10 x 10^-3

Thus, current density (J) = 2 x10^-3/ 10 x 10^-3

J = 0.20 A/m²

Therefore the  current density =  0.20 A/m²