permittivity

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Permittivity

A property of a dielectric medium that determines the forces that electric charges placed in the medium exert on each other. If two charges of q1 and q2 coulombs in free space are separated by a distance r meters, the electrostatic force F newtons acting upon each of them is proportional to the product of the charges and inversely proportional to the square of the distance between them. Thus, F is given by Eq. (1),

(1) 
where 1/(4&pgr;ε0) is the constant of proportionality, having the magnitude and dimensions necessary to satisfy Eq. (1). This condition leads to a value for ε0, termed the permittivity of free space, given by Eq. (2), where
(2) 
c is the velocity of light in vacuum.

If now the charges are placed in a dielectric medium that is homogeneous and isotropic, the force on each of them is reduced by a factor εr, where εr is greater than 1. This dimensionless scalar quantity is termed the relative permittivity of the medium, and the product ε0εr is termed the absolute permittivity ε of the medium.

A consequence is that if two equal charges of opposite sign are placed on two separate conductors, then the potential difference between the conductors will be reduced by a factor εr when the conductors are immersed in a dielectric medium compared to the potential difference when they are in vacuum. Hence a capacitor filled with a dielectric material has a capacitance εr times greater than a capacitor with the same electrodes in vacuum would have. Except for exceedingly high applied fields, unlikely normally to be reached, εr is independent of the magnitude of the applied electric field for all dielectric materials used in practice, excluding ferroelectrics. See Capacitance, Capacitor, Ferroelectrics

permittivity

[‚pər·mə′tiv·əd·ē]
(electricity)
The dielectric constant multiplied by the permittivity of empty space, where the permittivity of empty space (ε0) is a constant appearing in Coulomb's law, having the value of 1 in centimeter-gram-second electrostatic units, and of 8.854 × 10-12 farad/meter in rationalized meter-kilogram-second units. Symbolized ε.
References in periodicals archive ?
39) The only difference of the two-fluid formulations between the space plasma and brain plasma situations arise from the electric permittivity and magnetic permeability: in the former, the two parameters are those of the free space, [[epsilon].
On the other hand, their effectiveness falls when more complex and multirelaxed dispersive media are employed since the approximation does not accurately fit the frequency behavior of the electric permittivity.
c] are the positive electric permittivity and magnetic permeability, respectively, of material B in the limit [omega] [flecha diestra] [infinito].
0], which confirms the positivity of the electric permittivity of free space in the negative universe.
Based on electric permittivity and magnetic permeability in 2005 Richard W.
Anisotropic materials distinguish themselves through the tensorial structure of the electric permittivity and magnetic permeability.
If inclusions are regularly distributed and aligned, instead, the resultant homogeneous medium is anisotropic, and its electromagnetic parameters such as the electric permittivity should be described by a tensor [17].
When a CSRR is properly excited, a negative electric permittivity media is produced in the vicinity of the quasi-static resonant frequency.
Ferrite and CNT were used for fill the polymer in order to investigate their effects on electric permittivity, electrical conductivity and bonding mechanical resistance of formed materials.
The electric permittivity and the electric conductivity of each sample were evaluated using standard measurement techniques described in (Misra 1999) and (Heaney 1999).
It is well known that fishnet structures are composed of two parts: an array of thin metal wires parallel to the direction of electric field, which can be treat as "electric atoms" and results the effective negative electric permittivity ([epsilon]), and a pair of finite-width metal stripes separated by a dielectric layer along the direction of the incident magnetic field, which can be treat as "magnetic atoms" and results the effective negative magnetic permeability ([mu]).