The Fundamental Concept of Electric Current and Current Density

Topic Current density is essential in the fields of Physics and Electrical engineering. This concept is related to the notion of electromagnetism. The amount of electric energy travelling through a unit value of the cross-section is termed as current density. When this electric energy flows through a conductor, its density usually remains the same in every part of the conductor.

But in the case of altering current, the frequency of the flow of current is not constant in all parts of a conductor. Here we will discuss everything about the concept of current density.

What is Electric Current?

To know about Current Density, we first need to learn about what is Electric Current? Electric current means the flow of electrically charged particles through a conductor and the rate of electrical energy flow across any cross-section of a conductor is defined as current strength.Electric current is also seen as a flow of charged electrons. As when the two ends of a battery by using a metal wire, electrons flow from the electrically abundant end to the electrically deficit one. Also, the current always flows in a specific direction.

The symbol I signifies current, measured by the standard unit Ampere. 

Types of Electric Energy

Direct Current

Direct current is a type of current that constantly flows from one direction to another and the direction never changes. Also, the flow of the current is constant in Direct current. Direct current is also characterised by its zero frequency.

Alternating Current

In the case of Alternating Current, the energy always flows opposite the prominent direction. Though its frequency is constantly changing, it usually remains above zero. The magnitude of the flow also varies with time.

Free Current

Free Current is another type of electrical energy. It is assumed to be an energy flow with no such fixed route or direction and its frequency is also unstable. The ideal example of free current can be lightning bolts and the earth’s magnetic field currents. 

Units of Electric Current

S.I unit (Ampere)

 A charge of 1 Coulomb flowing across any of the cross-sections of a conductor in one second is termed as 1 Ampere. Thus, 1 Ampere= 1coulomb/ 1 second

C.G.S. electrostatic unit (ESU)

One ESU is the rate of the electric charge flow of 1 esu through any of the cross-sections of a conductor in one second. Thus, 1 ESU of current= 1 ESU of charge/ 1 second.

C.G.S. electromagnetic unit

One EMU is the rate of electric charge flow of 1 emu through any of the cross-sections of a conductor in one second. Thus, 1 EMU of current= 1 EMU of charge/ 1 second.

Current Density

An electric current signifies the flow of electrons from an electrically abundant source to a deficit one. Current is a macroscopic entity to which the concept of current density is related. The flow of the electric charge through any of the cross-sections of a conductor can be called current density. And this flow of the charge always remains the same through all the sections of a conductor.

The concept of current density is well exemplified through the flow of electrons from one battery to another. The current usually remains constant if its direction and magnitude remain constant.

Current Density Unit

The concept of current density and its measurement play a vital role in the field of electromagnetism. It means the rate of the flow of the electric charge in amperes per unit area of any cross section of a conductor or m2. The symbol J represents current density.

Current density is also considered a vector quantity as it has both the direction and the magnitude of the flow. The unit of electric or current density is Ampere per square metre or A/m2. Current that flows through a conductor is measured in terms of charge per unit of area (A) and per unit time (t).

The Formula for the Density of Current

If a conductor has a conductivity of σ, then follow the below-mentioned equation to find the density of electric current:

J= σ × E 

where J is current density,

Sigma (σ) is conductivity,

E is an Electric field

Also, the current density formula can be expressed in a different way:

J = I/A

where J is current density in A/m2,

A is the cross-sectional area in m2

Here, I refer to the flowing electric current through the conductor in Amperes (A).

Facts to keep in mind about the concept of Current Density

• Current is a macroscopic entity that means the flow of the electrons or electrically charged particles from one end of the conductor to another.

• There can be three types of currents: direct current, Alternating current and free current.

• Current density implies the flow of the electric charge through any of the cross-sections of a conductor.

• The symbol J represents current density.

• The formula of current density can be given as J= 1/A, where A is ampere.

• The unit of electric or current density is Ampere per square metre or A/m2.

Conclusion

The concepts of Current and Current Density plays an integral part in the study of electromagnetism and physics. Here, we discussed some significant aspects like the definition, symbol, current density unit and current density formula for your help. The concept of current density is difficult to grapple with for beginners, but you can start by simplifying the concept as basically a measurement of the density of electric current.