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Electric displacement

Auxiliary physical quantity of electromagnetics

This entry is made by Compilation and application of scientific encyclopedia entries of "Science Popularization China" to examine.

Electric displacement, also known as induction Strength refers to the description dielectric Auxiliary physical quantity of electric field. It is an auxiliary physical quantity used to describe the electric field, which is represented by the symbol D. Its definition formula is: D=ε zero E+P。 Where E is the electric field strength, P is the polarization strength, ε zero yes Vacuum permittivity 。 For linear isotropic dielectric, D=ε E, ε is dielectric Absolute permittivity 。

stay International System of Units In (SI), the unit of electric displacement is reservoir/square meter (C/m two )。

Chinese name: Electric displacement
Foreign name: electric displacement
Alias: induction strength

Properties: dielectric Auxiliary physical quantity of electric field
Field: electromagnetics
Related nouns: Electric displacement vector

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Introduction to terms

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describe dielectric Auxiliary physical quantity of electric field. also called induction strength. Defined as

Where

Is the intensity of external electric field;

by Electric polarization intensity ； ε zero by Vacuum permittivity 。 In linear Isotropy In dielectric,

，

by Electropolarizability , so

Where

yes Relative permittivity , which is a token Dielectric polarization Properties of the medium equation.

Produced after dielectric polarization polarization The charge has changed electric field Distribution, introducing auxiliary quantity

Is to prevent the unknown polarized charge from appearing in the electrostatic field Gauss theorem Thus, the calculation of electrostatic field in dielectric is greatly simplified.

stay International System of Units In (SI), the unit of electric displacement is reservoir/square meter (C/m two )。

Introduction and definition

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In the presence of dielectric in the electric field,^[1]

electric field intensity be equal to Free charge and polarization The superposition of fields excited by electric charge,

In vacuum Dielectric constant ， transposition Get:

Items in square brackets are only associated with charge density Therefore, the term in the brackets is called potential shift, namely:

(

by Vacuum permittivity For this dielectric Relative permittivity ；

by Electric polarization intensity ； International System of Units (SI) Unit: C/m two )

Gauss theorem

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For any closed surface S in space and the volume V enclosed by it, there are:

Q zero Is enclosed by the closed surface S Free charge Total.

Maxwell equation

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Differential form ：^[2]

Namely electric displacement divergence Equal to Point charge Density.

The advantage of this formula is that it is formally similar to polarization The charge is independent, which simplifies the discussion of the problem.^[3]

application

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When there is media, you can directly Free charge Find the distribution of

, and further obtain

And

。

Comparison of electric displacement and work done:

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