Electric Flux and Electric Flux DensityPublished on 22/6/2013 and last updated on 8/10/2018
Electric Flux DensityElectric flux density is defined as the amount of flux passes through unit surface area in the space imagined at right angle to the direction of electric field. The expression of electric field at a point is given by Where, Q is the charge of the body by which the field is created. R is the distance of the point from the center of the charged body. As, we know, Q = Ψ
The above equation can be rewritten as, This is the expression of flux per unit area since, 4πr2 is the surface area of the imaginary spare of radius r. This is the flux passing through per unit area at a distance r from the center of the charge. This is called electric flux density at the said point. We generally denote it with English letter D. Therefore, From, the above expression of D, it is clear that electric field intensity and electric field density are in same phasor.
As the number of electric lines of force emanated from a charged body is equal to the quantity of charge of the body measured in coulombs, we can also define the electric flux density at any point in the electric field of the body as the number of lines of force passing through a unit surface area at that point.