Define electric flux density and relative permitivity?

Electric flux density, also known as electric displacement field, is a vector quantity that represents the electric flux passing through a unit area perpendicular to the direction of the electric field. It is denoted by the symbol D and is measured in coulombs per square meter (C/m^2).

Relative permittivity, also known as dielectric constant, is a measure of how much a material can store electrical energy in an electric field. It is defined as the ratio of the electric flux density in a material to the electric flux density in a vacuum. It is denoted by the symbol εr and is a dimensionless quantity. Materials with a high relative permittivity are good insulators and can store more electrical energy.