Let us discuss electric current
Before we go to the actual discussion, we would like to tell you what does current means
Current means something is flowing. In an electrical circuit, if there is a voltage difference between two points, the electric charge flows
The rate of flow of electric charge with respect to time is called electric current
Let us assume a conductor. Let us consider one cross section of the conductor
We will also assume that a charge of dQ crosses this section in time dt
Now the current through the conductor can be expressed as I equals to dQ dt
If the charge passes through the cross section of the conductor is in coulombs
then the time taken by the charge to pass is in seconds
The unit of current would be expressed as coulomb per second. The unit coulomb per second is named as ampere
Ampere is the unit of electric current and 1 ampere of current equals to 1 coulomb by 1 second
So I ampere of current means I coulomb of charge passes through a cross section of a conductor in 1 second
In pure metallic conductor, movable charge is negative. Since this is contributed by free electrons in this conductor
As the movable charge is negative, it will move from negative side to positive side in a conductor
Previously it was thought that current is rate of positive charge flowing
The positive charge essentially flows from positive side to negative side of a conductor
So it was assumed that electrical current flows from positive side to negative side of a conductor
This direction is still taken as the direction of current. Although in metallic conductor, movable negative charge flows from negative side to positive side
But the conventional direction of current is taken in opposite of the flow of negative charge in the conductor
Such that the current is caused by flow of positive charge. This is conventional direction of current
Hope you got a basic idea. Thank you.