A-Level物理考试备考考点：电场与电场力

　　A-Level考试，是英国的普通中等教育证书考试高级水平课程，是英国的全民课程体系。物理考试是A-Level考试的一个部分，那么在复习物理时，考生要积累很多的知识点，本文今天就为大家带来的A-Level物理备考要点之电场与电场力，希望对考生们有所帮助，下面一起来看看。

　　A-Level物理考点：电场与电场力

　　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物理考试备考知识点的介绍，希望大家看了后对电场与电场力的相关问题有所了解，小编在此预祝大家都能取得好成绩！了解更多alevel考试试卷、alevel考试题型等问题，可咨询在线客服。