也谈均匀带电球面上的电场强度

在求解均匀带电球面上电场强度问题时存在的一种困惑 ,并给出避免困惑的几种不同的论证和求解方法。     

关于均匀带电球面上电场强度的求解

由于均匀带电球面上的电场强度无法用高斯定理求出,现行大部分大学物理基础教材在讨论均匀带电球面产生的场强分布时,只用高斯定理求出了该带电系统内外空间电场的分布,并没有给出球面上场强的计算方法,只是指出在球面上场强值不连续.文章利用叠加原理和电容器能量的变化两种方法分别导出了均匀带电球面上任一点的场强值,验证了均匀带电球面的场强是不连续的,两种方法思路截然不同,但得到的结果完全相同,该结果使得高斯定理求出的均匀带电球面在空间电场分布的结论更加完整.     

均匀带电球面上的电场强度如何计算

 对于电量ｑ均匀分布在半径为Ｒ的球面上的空间场强分布问题,许多大学基础物理教材(例如北京大学赵凯华、陈熙谋编的“电磁学”、陆果编的“基础物理学”和清华大学张三慧主编的“电磁学”等)中,利用高斯定理求出了如下的结果Ｅ=0,ｒ<Ｒｑ4πε0ｒ2,ｒ>Ｒ。教学中常有学生提问,当ｒ=Ｒ时,即在带电球面上的电场强度应为何值?现在来求解这个问题。首先要明确,我们不能采用高斯定理求解此问题。因为将高斯面取在球面上时,由于带电模型已经失效,无法确定高斯面所包围的电量,结果将是不确定的。我们可以采用功能原理来求解这个问题。     

均匀带电球面的电场强度分布再讨论

本文通过讨论球面内、外及球面上的电场强度，对均匀带电球面的电场强度分布作了新的诠释。     

计算均匀带电球面和柱面面上电场强度的另一方法

文中给出了计算均匀带电球面上和均匀带电柱面上电场强度的另一种方法．     

带电球面和带电球体电场强度和电势分布求解探讨

在大学物理静电场的教学中, 与球形有关的问题很典型, 比如带电球面和带电球体周围空间的电场强 度和电势分布问题, 不同电荷密度分布带电球体周围空间的电场强度和电势分布的求解问题, 本文对这些球形带电 体系进行分析探讨, 分别根据定义式求解和高斯定理求解, 并找出了其规律式和特点     

均匀带电半球面轴线上场强的计算

根据库仑定律和场强叠加原理,通过球面积分计算了均匀带电半球面轴线上的电场分布,包括球心处、球面上以及球面内外的电场强度,并给出电场随场点到球心距离变化的E-z曲线.计算和模拟结果表明,均匀带电半球面的电场大小并不是单调变化的,电场分布在球面半径处发生跃变,并在距球心约5倍半径处电场减小到趋于零.求解思路和计算结果可以为...     

均匀带电半球面球心场强的简便计算

半径为r均匀带电电荷面密度为σ的半球面,球心处电场强度的计算．一般用面积积分法,数学要求较高．本文介绍简化的导数法．     

均匀带电圆环的电场强度

求出了均匀带电圆环的电场强度,给出了它在3种坐标系里的表达式.     

均匀带电球面的电场场强分布再讨论

本文通过带电球面模型的建立，分析了均匀带电球面电场强度在球面突变的原因。     

Whispering Gallery Effect in Relativistic Optics

A relativistic laser pulse, confined in a cylindrical-like target, under specific conditions may perform multiple scattering along the internal target surface. This results in the confinement of the laser light, leading to a very efficient interaction. The demonstrated propagation of the laser pulse along the curved surface is just yet another example of the “whispering gallery” effect, although nonideal due to laser–plasma coupling. In the relativistic domain its important feature is a gradual intensity decrease, leading to changes in the interaction conditions. The process may pronounce itself in plenty of physical phenomena, including very efficient electron acceleration and generation of relativistic magnetized plasma structures.     

Relativistic Sagnac Effect and Ehrenfest Paradox

There seems to exist a dilemma in the literature as to the correct relativistic formula for the Sagnac phase-shift. The paper addresses this issue in the light of a novel, kinematically equivalent linear Sagnac-type thought experiment, which provides a vantage point from which the effect of rotation in the usual Sagnac effect can be analyzed. The question is shown to be related to the so-called rotating disc problem known as the Ehrenfest paradox. The relativistic formula for the Sagnac phase-shift seems to depend on the way the paradox is resolved. Kinematic resolution of the Ehrenfest paradox proposed by some authors predicts the usually quoted formula for the Sagnac delay but the resolution itself is shown to be based upon some implicit assumptions regarding the behaviour of solid bodies under acceleration. In order to have a greater insight into the problem, a second version of the thought experiment involving linear motion of a special type of a non-rigid frame of reference is discussed. It is shown by analogy that the usually quoted special relativistic formula for the Sagnac delay follows, provided the material of the disc matches the special type.     

巨共振激发的相对论效应

在相对论量子场论(QHD)的框架下,得到了相对论线性Vlasov方程.基此计算了球形核¹⁶O、⁴⁰Ca、⁹⁰Zr及²⁰⁸Pb的巨偶极共振的强度函数分布.计算得到的巨共振中心能量,与实验结果比较有较好的符合.对计算结果作了简要的讨论,发现核子有效质量m^*和平均场自旋轨道耦合力对巨共振能量有着重要的效应.     

耦合对相对论效应下的三次谐波的影响

研究了相对论效应引起的场量的非线性对谐波辐射源的影响；在入射光为长脉冲激光并计及各阶谐波间的耦合时，解析研究了三次谐波的振幅、频率、相位的变化及增长与饱和特性并计算了转化率，结果表明谐波间的耦合使幅值和转化率减少。     

巧推经典和相对论多普勒效应公式

无论是经典多普勒效应公式还是相对论多普勒效应公式,在大学物理教材中都可以找到其具体的推导方法,而且每种多普勒效应公式的推导方法都不止一种．但是这些推导方法均较为繁琐．笔者在实际教学过程中发现,通过建模,可以对两种多普勒效应公式进行非常巧妙的推导,特别是对于相对论多普勒效应公式,推导过程显得尤其简洁．     

Development and Application of the 2D Relativistic Fokker-Planck Package

The Fokker Planck package which without the relativity effect has been developed in 2002. The package with relativity effect, which induced from Italy, is now developed. It conrains relativity effect, and is bounce averaged. It can deal with such as the trapping effect, wave heating, neutral beam injecting, and particle losses. It is very useful for our HL-2A experimental results analysis.     

推导纵向相对论多普勒效应的新方法

基于狭义相对论的洛伦兹变换和同时的相对性,本文给出了一个推导长度收缩和纵向相对论多普勒效应的新方法。该方法可更直观理解在两个惯性系中观测一个纵向光波的波长与观测沿纵向静止于某个系中杆的长度的本质区别。     

The Effect of Interaction Range in Relativistic Microscopic Optical Potentials

Starting from the Walecka model about relativistic nucleon-meson field theory,the effect of interaction range in the relativistic microscopic optical potentials for nucleon-nucleus is included by folding the optical potentials in Local Density Approximity with nucleon-nucleon interaction potentials from the Walecka model.The present potentials are used to analyze the proton elastic scattering from nuclei.The agreement of the present calculation with experiment data is better than that of LDA.     

自旋相关相对论修正对重夸克偶素性质的研究

自旋相关的相对论修正对有限温度下重夸克偶素的结合和分解的影响进行了讨论,结果表明精细和超精细相互作用特影响对重夸克偶素性质的预言,特别是对ηc和J/ψ起着明显的作用.