Question

What is meant by charge and mention its unit.

Answer 1

Hint: When a charged particle is placed in an electric field or a magnetic, a force is exerted on the particle. When a charged particle accelerates, it produces electromagnetic waves. A charge can be positive as well as negative.

Complete answer:
Charge is a property of a substance that causes it to experience a force when placed in an electric field or a magnetic field. A charge can be positive as well as negative.
The SI unit of charge is Coulomb.

Additional information:
When two point charges (point sized particles with charge on them), say $q_1$ and $q_2$ are placed in vacuum at a distance r from each other, both of them experience an electric force of magnitude equal to ${\displaystyle \frac{K{q}_1{q}_2}{r^2}}$.
Here, K is a constant called permittivity of free space.
This law was given by Charles Coulomb called Coulomb’s law.
The magnitudes of gravitational force and electrical force are similar but the direction of force is different.
The direction of electrical force depends on the nature of charge (positive or negative charge).
Like charges (charges with the same nature, both negative or both positive) repel each other.
Unlike charges (charges with opposite nature, one negative and other positive) attract each other.

Note:
Note that charge is not a fundamental physical quantity. Current is considered as one of the fundamental quantities. Since current is charge flowing in one unit of time, charge will be current times the time.