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近几年高考物理试题中经常出现一类问题,其源于课本而又高于课本,该类问题一般条件隐蔽,难度较大,要求学生运用一些研究物理问题的方法,在科学分析的基础上进一步求解.本文以三道高考题为例,以期说明如何运用极限思想分析该类问题.例1(2012安徽卷)如图1所示,半径为R均匀带电圆形平板,单位面积带电量为σ,其轴线上任意一点P(坐标为x)的电场强度可以由库仑定律和电场强度的叠加原理求出:E=
In recent years, physical examination of college entrance examination often appear in a class of problems, which stems from textbooks but higher than the textbook, the general conditions of such problems hidden, more difficult, require students to use some of the methods of research on physical problems, based on scientific analysis Further solution.This article takes the three entrance examination questions as an example, in order to illustrate how to use the limit idea to analyze such problems.Example 1 (2012 Anhui volume) as shown in Figure 1, the radius of R uniformly charged round plate, the unit area of charge σ, the electric field intensity at any point P (coordinate x) on the axis can be calculated by the superposition principle of Coulomb’s law and electric field intensity: E =