Permittivity is a property of materials that resist electric charge. It is measured in farad per meter and coulombs per square meter. Vacuum permittivity is a constant value, while relative permittivity varies by medium. Complex permittivity can be affected by factors such as temperature and solutes. Permittivity is important in creating insulating materials and in applications where electrical energy needs to be efficiently transferred and stored.
Permittivity is a property exhibited by a substance in which it has an innate ability to resist an electric charge induced within its structure. This external electric field is usually referred to as the electric flux density and materials that resist the formation of the field are known as dielectrics or, more commonly, insulators. Measurement of this property is done in units of farad per meter as a measure of electrical capacitance, and electrical flux density is measured in coulombs per square meter, with a coulomb defined as a value of electric charge that can be transferred in one second where there is a constant current of one ampere. The electric permittivity values are therefore expressed as the ratio between the imposed electric flux density with respect to the effective strength of the electric field which is generated in the material.
Measures of this property also vary depending on the medium and are often expressed as vacuum or relative permittivity. The permittivity of vacuum is a pure measurement of the value in free or empty space, and is often referred to as the electric constant, or absolute or constant permittivity, and has a set value of 8.854187 x 10-12 farads per metre. Relative permittivity, on the other hand, is the representation of the electric flux density in a medium as it compares directly to what that value would be in a vacuum, where absolute permittivity is not restricted.
While the values for permittivity can often be quite simple to calculate, there are other factors in nature that influence them and can lead to a complex permittivity. The generation of this property only occurs when an electric field is applied, so the result can often be variable phase differences in a medium based on the material itself and the angular frequency of the electric field. Other factors such as temperature can also affect the results, and the complex permittivity of water is one example where temperature and dissolved solutes such as salt and other minerals in seawater versus freshwater can have a significant impact on the values. of permittivity. Changes in the permittivity of seawater are important for understanding the effects the medium has on the reflection of microwave radiation in global communications and for atmospheric science research.
In modern electronics, permittivity factors are important in creating insulating materials. This becomes increasingly important as integrated circuit components get smaller and smaller, down to a molecular atomic scale. Current leakage through transistors and other components in multilayer circuit designs can degrade the circuit or prevent it from functioning completely. In contrast to this need for effective dielectrics, materials with strong permittivity values are useful in capacitors, computer memory, and other applications where electrical energy needs to be efficiently transferred and stored.
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