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electrostatic field

The electric field observed when the observer is relatively static with the charge

Electrostatic field refers to Observer And Charge quantity Charge that does not change with time Relative static The electric field observed at. It is a special form of material existing in the space around the charge, and its basic feature is that it has a strong effect on the static charge placed in it, Coulomb's law This force is described.

Chinese name: electrostatic field
Foreign name: electrostatic field
Concept: Observer and Charge quantity The electric field observed when the charge that does not change with time is relatively static

Features: Strong effect on the static charge placed in it
Discipline: Physics, astronomy

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definition

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By static charge (relative to Observer Static charge) excited electric field 。

electrostatic field

nature

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According to the electrostatic field Gauss theorem ：

electrostatic field

Electrostatic Electric field line Starting from positive charge or infinity, ending at negative charge Or infinity, so the electrostatic field is Active field ．

from Ampere loop theorem It's a Irrotational field ．

According to the circulation theorem Circulation Identical to zero, indicating arbitrary closure along the electrostatic field Path movement Charge, Electric field force The work done is zero, so the electrostatic field is Conservative field ．

according to Coulomb's law , two Point charge Between Force With them Charge quantity The product of is proportional to and inversely proportional to the square of their distance, and the direction of the force is on their line, that is F =（ k · q1q2） / r two ; , where q1 、 q2 Is the amount of two charges (excluding the positive and negative) k by electrostatic force constant , about 9.0e+09 (N ·m two ）/（C two ;）， R is two charges Center point The distance of the line. be careful, Point charge Is regardless of its size, shape and charge distribution Situational Charged body 。 Is actual Charged body The idealized model of. When the distance between charged bodies is much larger than their size, the shape and size of charged bodies can be ignored.

Electrostatic induction

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When one charged object is close to another conductor charge distribution There are obvious changes. In physics, this phenomenon is called static electricity Induction 。

electrostatic field

If electric field There are conductors in the Electric field force Under the action of Charge separation , appears on the conductor surface. These charges are called Induced charge 。 The total electric field is the sum of induced charge and Free charge Joint action results. When equilibrium is reached field strength Zero everywhere, conductor is a Equipotential body , conductor surface is Equipotential surface , induced charges are distributed on conductors Outer surface , conductor surface Electric field direction Perpendicular to the conductor surface everywhere. Electrostatic induction has some applications, but it may also cause harm.

Medium in field

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Static Field Knowledge Structure Diagram

Electric field Insulating medium Also known as dielectric 。 Due to the effect of electric field force, the equivalent Bound charge 。 This phenomenon is called polarization of dielectric 。 For one Insulating material When the electric field strength exceeds a certain value, the bound charge is forced to flow Dielectric breakdown And lose it Insulation performance 。 Therefore, the size of the electrostatic field is very important for the design of electrical devices and the selection of materials. The electrostatic field in the presence of a medium is generated by the bound charge and the free charge. In order to express the electric field under the combined action of the two, another field vector can be introduced flux Density D (also called Electric displacement ）。 It is defined as

Where P Dielectric Polarization intensity , we can get Gauss flux theorem

formula

Where q Only S All free charges in the plane, excluding the bound charges of the dielectric. Gauss flux theorem Differential form Potentially shifted divergence Equal to the free charge (volume) density at this point ρ ，

Dielectric polarization P And electric field strength E And the electric flux density is related to P and E Therefore, it can be concluded that Constitutive equation

D =ε E

potential

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Because the electrostatic field is Irrotational field , so available scalar The potential φ represents the electrostatic field (see potential). Potential and electric field intensity The relationship between

Where Q Point is Potential reference point , optional at infinity; P The point is the observation point. Supra Differential form Is the negative gradient of the electric field intensity equal to the potential, namely

E =-∇ φ In the region where ε is constant,

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In the formula, "R" can be recorded as "R 2" Cartesian coordinates in

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First order and second order Differential operator 。 In this way, the potential can be obtained φ Satisfied differential equation

electrostatic field

be called poisson equation 。 If the observation point is free charge density ρ Is 0, then

∇2φ=0

be called Laplace equation 。 Poisson equation and Laplace equation Describes the spatial distribution of electrostatic field Regularity 。 It can be proved that when the ρ , ε and boundary condition Poisson equation or Laplace equation Solution of the equation Is unique and can try to solve the potential φ , and then ask for E 。

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