Electric current is the flow of the electric charge in the form of free electrons. The current is measured by the number of free electrons passing the particular point within the circuit per second.
Therefore the flow of charge per unit second describe the amount of electric current. When the charge moves at the rate of 6.25 x 1018 electrons flowing past the given point per second the value of the current is one ampere.
This is the same as saying one coulomb of charge per second.
The SI (International System of Units) unit of current is the Ampere with symbol A. A constant current has symbol I, while the time-varying current has a symbol i for intensity.
Mathematically can define the relationship between charge (Q) and electric current (I) as:
[pmath]I= Q/t[/pmath] [pmath]amperes=coulombs/seconds[/pmath]
I(amperes)= Average Current flowing
Q(coulombs)= Total Charge passing the fixed point
t(seconds)= Time taken to pass the point
“An electric current of one ampere flows in a circuit when a charge of one coulomb passes a given point in one second”
Electric current has the direction associated with it. Conventional current flow is in the direction of positive charge movement from positive to negative. Electron flow is in the opposite direction from negative to positive. The arrow in the circuit specifies the direction of positive current flow. In solid metals only the negatively charged free electrons move to produce the current flow, the positive protons can not move but in the liquid or gas both the positive protons and negative electrons move to produce a current flow.
Since electric circuits consist almost entirely of solid metal conductors such as copper wire, only negatively charged electrons produce the current flow. Current is also the measure of how intense or concentrated the electron flow is.