Scientist Michael Faraday brought the concept of electric field in the 19th
century. He used the patterns of electric field lines that shows the existence of the electric field
but these lines are invisible in reality. He explained
that around a charge particle there a space in which another charge
particle experience a force of attraction or repulsion, this region is
called the electric field.

Electric Field Definition

When electric charges acts in certain region of space. They produce
force around it. This is what electric field is! It decides whats the
strength the field carries due to these charge interaction. Hence, the electric field is defined as"Electrical force acting per unit charge exerted on the charged body".

Electric Field Lines

Electric field lines (electric flux lines) are the curved or straight paths along which a unit positive charge tends to move in the electric field if it is free to do so. These lines are imaginary but they give us the pictorial visualization of electric field. They show patterns of several lines, which extend between infinity and the source charges.

Electric Field Strength

The electric field is a region where force acts due to the interaction between the charges. The strength of the field is measured as

Electric field strength = $\frac{Force}{Charge}$

or

E = $\frac{F}{q}$

The unit of electric field strength is in newton per coulomb (NC-1). It is a vector quantity. It obeys inverse square law. Hence, if a charge q is at a distance r from another charge Q, the force between them is given as

Electric Field in a Capacitor

A parallel plate capacitor consists of two conducting metal plates X and Y each of area A separated by distance d. The plates can be of any shape. When the plates are connected to a battery, a charge +q appears on plate X and – q appears on plate Y. On each plate the charge is distributed uniformly. As the distance between the plates is small compared to the area of the plate, the electric field is uniform between the plates. The electric field is non uniform at the outer edge of the plates.

The electric field E acting in a parallel plate capacitors is given by

E = $\frac{\sigma}{\epsilon_o}$ = $\frac{V}{d}$

where $\epsilon_o$ is the permittivity of free space and d is the distance between the plates