### Theory:

Electric current is known as the flow of electric charges in a particular direction. The amount of electric charges passing through a conductor in one second is known as the magnitude of electric current.
The formula is written as,

$\begin{array}{l}\mathit{Electric}\phantom{\rule{0.147em}{0ex}}\mathit{current}=\frac{\phantom{\rule{0.147em}{0ex}}\mathit{Amount}\phantom{\rule{0.147em}{0ex}}\mathit{of}\phantom{\rule{0.147em}{0ex}}\mathit{electric}\phantom{\rule{0.147em}{0ex}}\mathit{charge}}{\mathit{Time}}\\ \\ I=\frac{Q}{t}\end{array}$

Where, $$I$$ is the electric current, $$Q$$ is the electric charge, and $$t$$ is the time of charge flow.

Сoulomb ($$C$$) is the unit of electric charge, and Ampere ($$A$$) is the SI unit of electric current.
One ampere is the amount of current flowing through a conductor if one coulomb of charge flows through it in one second.
In other words, Ampere is a unit of electric current equal to a flow of one coulomb per second.

Measuring device
An ammeter is an instrument used for measuring electric current in a circuit.

A battery, an ammeter and a bulb connected in series make a simple electric circuit. An ammeter can measure the current flowing in an electric circuit.

Solved example
When $$3$$ coulomb of charge flows through a circuit for $$15$$ $$seconds$$, what will be the amount of current flowing through it?

Charge, $$Q$$ $$=$$ $$3\ C$$

Time, $$t$$ $$=$$ $$15\ s$$

$\begin{array}{l}I=\frac{Q}{t}\\ \\ =\frac{3}{15}\\ \\ =\phantom{\rule{0.147em}{0ex}}0.2\phantom{\rule{0.147em}{0ex}}A\end{array}$

Thus, the current flowing through the circuit is $$0.2\ A$$.
Reference:
https://live.staticflickr.com/3818/13691094544_4f0b389176_b.jpg
https://live.staticflickr.com/3816/13691080074_ba71abaf5d_b.jpg