2004/12/09 | D[D]
类别(Ω〖物理〗) | 评论(0) | 阅读(20) | 发表于 13:01
A vector quantity that allows Gauss's law to be written in terms of free charge alone as
(1)

in a dielectric having a bound charge
(2)

where P is the electric polarization.D is sometimes called the electric displacement.

In cgs, D is given by
(3)

(4)

(5)

where is the electric susceptibility and is the dielectric constant (Purcell 1985, p. 381). In MKS,
(6)

(7)

(8)

where is the permittivity of free space and is the dielectric constant.
It should be emphasized that unlike for electrostatic fields,
(9)

is not, in general, equal to . Therefore, it is not possible to write D as the gradient of a scalar potential. However, in cases of spherical, infinite cylindrical, or planar symmetry, it turns out that (Griffiths 1987, p. 156).

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