Displacement current
Displacement current is a quantity appearing in Maxwell’s equations. Displacement current definition is defined in terms of the rate of change of the electric displacement field (D). It can be explained by the phenomenon observed in a capacitor.
When a capacitor starts charging, there is no conduction of charge between the plates. However, because of the change in charge accumulation with time above the plates, the electric field changes causing the displacement current as below-
\(I_D =J_DS= S\frac{\partial D}{\partial t}\)
Where,
- S is the area of the capacitor plate.
- ID is the displacement current.
- JD is the displacement current density.
- D is related to electric field E as D = εE
- ε is the permittivity of the medium in between the plates.
Electric displacement
Electric displacement, denoted by D, is the charge per unit area that would be displaced across a layer of conductor placed across an electric field. It is also known as electric flux density.
Electric displacement is used in the dielectric material to find the response of the materials on the application of an electric field E. In Maxwell’s equation, it appears as a vector field.
The SI unit of electric displacement is Coulomb per meter square ( m-2).
The mathematical representation is as follows:
\(D \equiv \epsilon_0E + P\)
Where,
- ϵ0: Vacuum permittivity
- P: Polarization density
- E: Electric field
- D: Electric displacement field
It was found that if electric field E is applied on the dielectric material, the bound charges inside the material responds to the electric field such that the distribution of positive changes take place in the direction of the electric field while the distribution of negative charges takes place in the opposite direction of the electric field. Before the application of the electric field, the material is electrically neutral and there is a formation of electric dipoles.
