Current Definition:
Current is defined as flow of electrically charged particles, mostly in those atoms which are electrondeficient. The standard symbol of current is capital I. The standard unit of current is ampere and it is denoted by A. Conversely, a current of one ampere is one coulomb of charge(6.24 x 10^{18} charge carriers) going past a given point per second. According to Physicists, Current is considered to move from relatively positive to negative points, and this is known as conventional current. Electrons are known to be the common negatively charged carriers and circulate from relatively negative to positive points.
Current can be divided into two types.

Direct Current:
Direct current travels towards the same direction at all points, although the instantaneous magnitude can differ.

Alternating Current:
The flow of charge carriers is towards opposite direction periodically in an alternating current.
The number of AC cycles per second is known as frequency and calculated in hertz. An example of DC is current generated by an electrochemical cell.
Current density:
The amount of electric current travelling per unit crosssection area is called as current density and expressed in amperes per square meter. More the current in a conductor, higher will be the current density. However, the current density alters in different parts of electrical conductor and the effect takes place with alternating currents at higher frequencies.
Electric current always creates a magnetic field. Stronger the current, more intense is the magnetic field. Varying AC or DC creates an electromagnetic field and this is the principle based on which signal propagation takes place.
Current density is a vector quantity having both a direction and a scalar magnitude. The electric current flowing through a solid having units of charge per unit time is calculated towards the direction perpendicular to the flow of direction.
It is all about the amount of current flowing across the given region.
Current Density Formula:
The formula for Current Density is given as,
J = I / A
Where,
I = current flowing through the conductor in Amperes
A = cross sectional area in m^{2}.
Current density is expressed in A/m^{2}.
Current Density Calculation Example:
Determine the current density when 40 Amperes of current is flowing through the battery in a given area of 10m^{2}.
Solution:
It is given that,
I = 40 A,
Area = 10 m^{2}
The current density formula is given by,
J = I / A
= 40 / 10
J = 4 A/m^{2}.
To know more about current density of copper, ohm’s law and current density calculator along with formula in semiconductors @Byju’s.
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