Define S.I. unit of charge.

Hint:Recall the basics of an electric charge and the unit of the electric charge. From this definition, determine the basic unit of the electric charge and the unit of the charge named after the scientist. From these units, give the definition of the unit of an electric charge.

Complete answer:
The property of matter by virtue of which it experiences a force when it is placed in an electric field is known as electric charge. The SI units of charge are Ampere-second or Coulomb. When one ampere of electric current flows through the current carrying conductor for one second, then the amount of charge through the conductor is one coulomb.
\[1\,{\text{coulomb}} = \left( {{\text{1 ampere}}} \right)\left( {{\text{1 second}}} \right)\]

Additional information:
The mathematical expression for the electric charge is given by
\[Q = It\]
Here, \[Q\] is the electric charge, \[I\] is the electric current and \[t\] is the time for which the electric current flows through the conductor.
The charge on one electron is equal to \[1.6 \times {10^{ - 19}}\,{\text{C}}\].
\[{q_e} = 1.6 \times {10^{ - 19}}\,{\text{C}}\]

The charge 1 coulomb is equal to the charge of \[6.242 \times {10^{18}}\] number of electrons.
\[1\,{\text{C}} = 6.242 \times {10^{18}}{q_e}\]
There are two types of charges which are positive charge and negative charge.There is force of attraction between two opposite charges and force of repulsion between two like charges.

Note: The students may think that electric charge can have two SI units. They should keep in mind that ampere-second and coulomb explained in the above solution are both SI units of the electric charge. The unit ampere-second is determined from the formula of the electric charge and the unit coulomb is named after the scientist Charles-Augustin de Coulomb.