Some books define (although some do not) the electric field flux as the number of electric field lines passing through a given area.
Suppose that there is a electric field created by a charge plate and the field lines emerging from the plate are passing through two adjacent media having two different permittivities. In this case, the electric fields observed in two media should be different due to the differences in electric permittivities. So when the electric filed line model is applied here, which tells something about the field strength, we see that number of filed lines in two media are different.
Does this mean that electric filed lines are created or destroy at the interface between media? I know obviously this is not the case, but how can we explain this situation? Should we apply the electric flux model separately to two media considering them individually?
Best Answer
The electric field can be considered to start and end on total charges represented by the sum of free and bound charges in the material. At the interface of two different dielectrics with different polarizations P a net bound charge appears which is the source and sink of the electric field lines in addition to free charges. Therefore the electric field lines can start and end on the dielectric interfaces in contrast to the displacement field lines which start and end only on free charges.