31-08-2017, 10:22 AM
A dielectric (or dielectric material) is an electrical insulation that can be polarized by an applied electric field. When a dielectric is placed in an electric field, the electric charges do not flow through the material as they do in an electrical conductor, but only change slightly from their average equilibrium positions, causing dielectric polarization. Due to the dielectric polarization, the positive charges move towards the field and the negative charges change in the opposite direction. This creates an internal electric field that reduces the overall field within the dielectric itself. If a dielectric is composed of weakly bonded molecules, these molecules not only polarize, but also reorient themselves so that their symmetry axes align with the field.
The study of dielectric properties refers to the storage and dissipation of electrical and magnetic energy in materials. Dielectrics are important in explaining various phenomena in electronics, optics, solid state physics and cellular biophysics. Although the term "insulation" implies low electrical conduction, "dielectric" typically means materials with a high polarisability. The latter is expressed by a number called the relative permittivity (also known in ancient texts as dielectric constant). The term "insulation" is generally used to denote electrical obstruction while the term "dielectric" is used to indicate the energy storage capacity of the material (by means of polarization). A common example of a dielectric is the electrically insulating material between the metal plates of a capacitor. The polarization of the dielectric by the applied electric field increases the surface charge of the capacitor for the given electric field strength.
The term "dielectric" was coined by William Whewell ("electric-day") in response to a request from Michael Faraday. A perfect dielectric is a material with zero electrical conductivity (see perfect conductor), thus showing only a displacement current; therefore it stores and returns the electrical energy as if it were an ideal capacitor.
The study of dielectric properties refers to the storage and dissipation of electrical and magnetic energy in materials. Dielectrics are important in explaining various phenomena in electronics, optics, solid state physics and cellular biophysics. Although the term "insulation" implies low electrical conduction, "dielectric" typically means materials with a high polarisability. The latter is expressed by a number called the relative permittivity (also known in ancient texts as dielectric constant). The term "insulation" is generally used to denote electrical obstruction while the term "dielectric" is used to indicate the energy storage capacity of the material (by means of polarization). A common example of a dielectric is the electrically insulating material between the metal plates of a capacitor. The polarization of the dielectric by the applied electric field increases the surface charge of the capacitor for the given electric field strength.
The term "dielectric" was coined by William Whewell ("electric-day") in response to a request from Michael Faraday. A perfect dielectric is a material with zero electrical conductivity (see perfect conductor), thus showing only a displacement current; therefore it stores and returns the electrical energy as if it were an ideal capacitor.