Mention the $SI$ unit and value of fundamental charge. Write its smaller units.

Electric charge of electron is called fundamental charge. Its symbol is $e$ and charge is negative.

In the international system ($SI$) of units, a unit of charge is called a coulomb and is denoted by

the symbol $C$.

One coulomb is the charge flowing through a wire in $1 \mathrm{~s}$ if the current is $1$ $A$ (ampere).

In this system, the value of the basic unit of charge is, $e=1.602192 \times 10^{-19} \mathrm{C}$. In general it is taken

as $e=1.6 \times 10^{-19} \mathrm{C}$.

There are about $6.25 \times 10^{18}$ electrons in a charge of $-1 \mathrm{C}$.

In electrostatics, smaller charges are :

$1 \mathrm{mC}$ (milli coulomb) $=10^{-3} \mathrm{C}$

$1 \mu \mathrm{C}$ (micro coulomb) $=10^{-6} \mathrm{C}$

$1 \mathrm{nC}$ (nano coulomb) $=10^{-9} \mathrm{C}$