Question

What is meant by Electric flux density?

Answer 1

In order to answer this problem we should first understand about electric flux. The total number of electric lines of force originating from a charged body is known as electric flux. Electric flux is the representation of an electric field.

Complete step by step answer:
Electric flux lines are not always closed loop. This is due to the fact that while an isolated magnetic north pole or south pole does not exist in practise, an isolated positively charged body and an isolated negatively charged body can. Electric flux is commonly denoted by the symbol. The amount of flux emitted by one coulomb positive electric charge is used as the measuring unit of flux. We know that the number of lines of force emitted by a positive charge body is numerically equivalent to the coulomb charge of the body.
The quantity of flux passing through a unit surface area in a region imagined at right angles to the direction of the electric field is known as electric flux density. The formulation for the electric field at a given place is
$E = \dfrac{Q}{{4\pi {\varepsilon _ \circ }{\varepsilon _r}{r^2}}}$
Where, $Q$is the charge of the body by which the field is created. $r$is the distance of the point from the centre of the charged body.
As, we know, $Q{\text{ }} = {\text{ }}\Psi$
So can write the above equation :

$E = \dfrac{\Psi }{{4\pi {\varepsilon _ \circ }{\varepsilon _r}{r^2}}} \Rightarrow {\varepsilon _ \circ }{\varepsilon _r}E = \dfrac{\Psi }{{4\pi {r^2}}}$
Since $4\pi {r^2}$ is the surface area of the imaginary spare of radius $r,$this is the formula for flux per unit area. This is the flux per unit area travelling through the charge at a distance of r from the centre. This is referred to as the electric flux density at the specified place. It's usually represented by the letter $D$ in English. Therefore,
$D = {\varepsilon _ \circ }{\varepsilon _r}E$

Note: We can define the electric flux density at any point in the electric field of a charged body as the number of lines of force passing through a unit surface area at that point because the number of electric lines of force emanated from the charged body is equal to the quantity of charge measured in coulombs.