Physics

An object's solid angle in steradians is equal to the area of the segment of a unit sphere, centered at the angle's vertex, that the object covers.

$Ω=r_{2}S $

While electric flux is the measure of the flow of the electric field through a given area. It is proportional to the number of electric field lines passing normally through a perpendicular surface.

$D=ϵE$ -----[Equation 1]

In Equation [1], $ϵ$ is the permittivity of the medium (material) where we are measuring the fields.

The Electric Field is equal to the force per unit charge:

$E=4πϵR_{2}q_{1} $------[Equation 2]

Then the Electric Flux Density is:

$D=ϵE=4πR_{2}q_{1} $--------[Equation 3]

From Equation [3], the Electric Flux Density is very similar to the Electric Field, but does not depend on the material in which we are measuring (that is, it does not depend on the permittivity. Note that the $D$ field is a vector field, which means that at every point in space it has a magnitude and direction.

The Electric Flux Density has units of Coulombs per meter squared [$C/m_{2}$].