Practical Relevance
The dielectric constant is an essential piece of information when designing capacitors, and in other circumstances where a material might be expected to introduce capacitance into a circuit. If a material with a high dielectric constant is placed in an electric field, the magnitude of that field will be measurably reduced within the volume of the dielectric. This fact is commonly used to increase the capacitance of a particular capacitor design. The layers beneath etched conductors in printed circuit boards (PCBs) also act as dielectrics.
Dielectrics are used in RF transmission lines. In a coaxial cable, polyethylene can be used between the center conductor and outside shield. It can also be placed inside waveguides to form filters. Optical fibers are examples of dielectric waveguides. They consist of dielectric materials that are purposely doped with impurities so as to control the precise value of εr within the cross-section. This controls the refractive index of the material and therefore also the optical modes of transmission. However, in these cases it is technically the relative permittivity that matters, as they are not operated in the electrostatic limit.
Read more about this topic: Relative Permittivity
Famous quotes containing the words practical and/or relevance:
“The ordinary literary man, even though he be an eminent historian, is ill-fitted to be a mentor in affairs of government. For ... things are for the most part very simple in books, and in practical life very complex.”
—Woodrow Wilson (1856–1924)
“The most striking fault in work by young or beginning novelists, submitted for criticism, is irrelevance—due either to infatuation or indecision. To direct such an author’s attention to the imperative of relevance is certainly the most useful—and possibly the only—help that can be given.”
—Elizabeth Bowen (1899–1973)