Electric Current: What is it? 

Electric Current

Electric current can be defined as the flow of charged particles through an electrical conductor in a definite direction. It is the rate of flow of electric charge via conducting medium. Electric current is denoted by using the symbol I or I and the unit is Ampere or Amp. It is denoted by the letter A.

Mathematically, we can express the flow of charge per unit of time by:

I = dQ/dt

In another word, a stream of charged particles moving through an electrical conductor is an electric current. The flowing charged particles are known as charge carriers that may be electrons, ions, holes, etc.

During the normal state, there will be only random motion of free electrons in a conductor which doesn’t possess any electric current as there won’t be a net transfer of charge across a cross-sectional area.


Cross-sectional area of a metal = A

Number of free electrons in metal (m3) = n

Drift velocity of electrons (m/s) = v

Distance moved by electrons in a small time interval of dt = dx

                                                                               = vdt

Charge of an electron = e

Volume swept in time dt = dx X A

Therefore, Net number of electrons transfer across dx section in dt sec = nAvdt

Also, Net charge transfer across dx section in dt sec is

 dq = neAvdt.


 Electric current, I = dq/dt

                       = neAvdt/dt

Hence I = neAv(coulombs/sec or ampere)

Current Density, J = i/A = nev (A/m2)