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A-Level物理考点：电场与电场力

英国高中课程（General Certificate of Education Advanced Level）简称A-Level课程，它是英国的普通中等教育证书考试水平课程，是英国的全民课程体系。今天，小编为大家带来的是A-Level物理备考要点之电场与电场力的相关资讯，希望对准备考试的你有所帮助！

Part 1 Electric Field Shapes 电场概念及表示

Electric Field

“An electric field is a region in which particles with charge experience a force”

Field Shape Diagrams

We represent electric fields with diagrams that have conventions (or rules)

that need to be followed.

For example:

The field lines (and arrows) show the direction of the force that would be felt by a positive charge at that point in the field. Note that unlike gravitational fields, electric fields can attract or repel objects.

The spacing between the lines shows how strong the field is at that point. In this case it's strongest near to the charge because the lines are closest there.

This field is uniform because the spacing between the lines remains the same throughout the field shown. The field lines are parallel and equispaced.

Part 2 Electric field strength 电场强度

This is defined as the force per unit charge acting at a point in the field.

So an equation for it is:

Where:

E = electric field strength

F = force acting in newtons

q = the charge in coulombs

Units of E: NC-1 or Vm-1 (these are the same thing!!)

(1)匀强电场Uniform Fields

There is one special example you also need to know :

This is a uniform field. The field strength at any point in this field

is:

where

V = the pd between the plates

d = the distance separating the plates.

Field strength is a vector - it has direction as well as magnitude.

This is important to remember because in electric fields you can have field

strengths acting in different directions due to different signs of charge.

Radial Fields

A particularly useful equation to find field strength around a point charge

(note - the first pictures is the field diagram section were point charges)

is:

where

Q = the charge causing the field

r = the separation between the charge and the point you are considering

ε = permittivity (see below for notes).

以上是小编给大家带来的A-Level物理备考要点之电场与电场力的相关资讯，希望对考生们的备考有一定帮助！