Dielectric constant, also known as the dielectric constant, dielectric coefficient or permittivity, it is a coefficient that represents the insulation capacity characteristics, expressed by the letter ε, the unit is law\/meter.
It is a proportional constant between the displacement of electricity and the strength of the electric field. This constant in free space (a vacuum) is 8.85×10 to the -12 Faraday per meter (F\/m). In other materials, the dielectric coefficient can vary greatly, often much higher than the value in vacuum, and is marked by the symbol eo.
In engineering applications, the dielectric coefficient is often expressed as a relative dielectric coefficient rather than an absolute value. If eo represents the permittivity of free space (that is,8.85×10 to the -12 power F\/m), and e is the permittivity of the material, then the relative permittivity of the material (also known as the permittivity) is given by the formula: ε1 = ε \/ εo = ε×1.13×10 to the 11 power
Many different substances have permittivity greater than 1. These substances are often called insulating materials, or insulators. Commonly used insulators include glass, paper, mica, a variety of different ceramics, polyethylene, and specific metal oxides. Insulators are used for alternating current. Foam with polystyrene, polyvinyl chloride, polyurethane and other resins made of polystyrene 2.2.6, the permittivity has a relative permittivity and effective permittivity, usually we say the dielectric constant is the relative permittivity, the relative permittivity of silicon is 11.9 Capacitors and transmission lines for (AC), sound wave (AF) and radio wave (RF).
When a capacitor plate is filled with a material with a dielectric constant of ε, the capacitance becomes ε times larger