费曼佯谬与电磁场角动量守恒

带电体在转动过程中，机械和电磁场联合系统角动量守恒，本文首先介绍费曼佯谬，然后从理论上提出电磁场角动量的概念，导出电磁场角动量守恒定律，并用带电体与电磁场联合系统角动量守恒的原理揭示了费曼转盘转动的机理。     

两个同心带电球壳体系电磁场角动量的研究

电磁场的动量和角动量是经典电磁学有趣而又基本的问题。根据标准电磁理论,电磁场角动量可表示为L_(em)=ε_0∫_vr×(E×B)dV,对恒定电磁场,角动量还可以用L_(em)=∫r×ρAdV来计算,文章对此进行了分析。通过一个简单的模型,即一个固定的绝缘带电球壳处在另一个旋转的绝缘带电球壳中心,分析了该体系电磁场从建立到稳定,再到撤去的过程中,整个系统角动量的变化情况。验证了在建立稳定电磁场的过程中,外力提供的冲量矩一部分转化为电磁场角动量储存在电磁场中,一部分提供体系的转动机械角动量,当撤掉磁场后,电磁场角动量转换成机械角动量,整个过程角动量守恒。     

一个验证电磁系统角动量守恒的实例

本文从一个实验出发，就电磁角动量、电磁场角动量流密度张量和机械角动量进行讨论，给出带电体系角动量与场角动量守恒的条件．     

关于电子-磁单极子的经典角动量

电子在磁单极子场中的特殊性质,很早就有所讨论,静止的电子-磁单极子(e-g)体系的电磁场带来的附加角动量,是众所周知的,将此附加角动量叠加到轨道角动量中,给出此体系的总角动量.这里有两点值得进一步探讨,首先,我们知道,体系的角动量守恒是由空间转动不变性所决定的,那么e-g体系的角动量如何由空间转动不变性导出,其次,e-g体系的总角动量,除了计入静态场的附加角动量外,还有否其他的贡献.本文对此作简短讨论. 早先Dirac在讨论磁单极子的电磁场时,电磁势有奇异性,存在奇异弦使体系的拉氏     

电磁场角动量守恒定律的简明推导

对电磁场角动量守恒定律作了一种简明的推导。     

费曼圆盘佯谬及角动量守恒

简述电磁场中角动量守恒定律和费曼圆盘佯谬，对描述费曼圆盘的模型进行了讨论，最后对静场远区的角动量作了定量计算。     

电磁场中的角动量是怎样调集进去的──费曼圆盘佯谬与角动量守恒的初等论证

本文以费曼所提出的圆盘佯谬为例，首先计算出磁场消失过程中圆盘所获得的机械角动量，再分析在建立稳态电磁场过程中升力矩的作用，由动量矩定理引入电磁角动量的概念，进而对佯谬中的角动量守恒给出定量的论证．     

空间对称性与电磁角动量守恒

阐明空间对称性与守恒律，并结合电磁场中带电粒子的拉氏函数，巧妙简捷地处理了一个电磁系统的角动量守恒。     

电磁学与电动力学中的磁单极-I

本文及后继三篇文章在电磁学和电动力学框架内分别介绍磁单极的若干奇特性质.针对由一个磁单极和一个点电荷构成的体系,首先证明这个体系的电磁场角动量具有极简洁的表达式并讨论可能的电荷量子化,然后显式地演示体系角动量的转化与守恒.     

电容器和螺绕环转动时电磁场的角动量

分别计算了理想的圆柱形电容器、 圆形平行板电容器和螺绕环这三者绕各自中心对称轴做定轴转动 时电磁场对转轴的角动量.计算结果或许没有什么实用价值, 但应该具有一定的理论认识价值, 即该计算结果从一 个侧面体现了电磁场这种物质形态的一点特殊性     

推导平方反比有心力场中质点轨道的一种方法

根据动量定理和角动量定理，通过直角坐标系和平面极坐标系单位矢量的变换，给出了推导平方反比有心力场中轨道的一种新方法．     

旋转带电体和电磁场的角动量守恒定律及能量守恒定律

对均匀带电薄球壳匀加带旋转问题,由电磁场的角动量定恒守律和能量守恒定律两种方法分别得出了外力矩力其功率的正确正确结果。     

Filed Approach to Classical Mechanics

We show that in classical mechanics the momentum may depend only on the coordinates and can thus be considered as a field. We formulate a special Lagrangian formalism as a result of which the momenta satisfy differential equations which depend only on the coordinates. The solutions correspond to all possible trajectories. As a bonus the Hamilton-Jacobi equation results in a very simple way.     

Effects of magnetic field on the evolution of the wave function of a charged particle with an angular momentum

We have calculated the effect of a magnetic field on the evolution of angular momentum eigenfunctions of a charged particle. An additional harmonic potential is supplemented to trap the wave packet. We find the probability density of the wave function is oscillating in the radial direction with a time period determined by the strength of the effective harmonic potential. When the magnetic field is along the z direction, if the initial wave function is an eigenfunction of ${\hat{L}}_{z}$, the probability density of the particle remains axis-symmetric. While for the case of an eigenfunction of ${\hat{L}}_{x}$, it is anisotropic in the x−y plane and rotates with a time period inverse proportional to the strength of the external magnetic field. We also extend the results in a phenomenological way to the case with an external magnetic field that varies harmonically in time.     

巧造水火箭

利用可乐瓶、气筒气管等简易材料制作了水火箭,利用该装置演示了动量守恒原理,并给出了实验注意事项.     

自制动量矩守恒演示仪

本文介绍了一种自制的动量矩守恒演示仪，该仪器具有小巧、美观、灵活、稳定、方便等特点。     

Analysis of the Abraham-Minkowski Controversy by Means of Two Simple Examples

Using a very simple example, H. M. Lai [1] argued in favor of Abraham's proposal for defining electromagnetic field momentum density. Later, using another simple device, Johnson et al. [2] argued in favor of Minkowski's proposal. This indicates that the Abraham-Minkowski controversy remains open. Both models consider nonmagnetic media ( = 1). In this work we analyze both models pointing out some weak points and extend the analysis to magnetic media ( 1). We show that in this case Minkowski's proposal is better than Abraham's. Our analysis throws some light on this very old controversy.     

Inconsistencies of the U(1) Theory of Electrodynamics: Stress Energy Momentum Tensor

The internal gauge space of electrodynamics considered as a U(1) gauge field theory is a scalar. This leads to the result that in free space, and for plane waves, the Poynting vector and energy vanish. This result is consistent with the fact that U(1) gauge field theory results in a null third Stokes parameter, meaning again that the field energy vanishes in free space. A self consistent definition of the stress energy momentum tensor is obtained with a Yang Mills theory applied with an O(3) symmetry internal gauge space. This theory produces the third Stokes parameter self consistently in terms of the self-dual Evans-Vigier fields B(3).     

Orbital angular momentum of channeling radiation from relativistic electrons in thin Si crystal

We propose to use channeling radiation (CR) from relativistic electrons as a source of high energy twisted photons in the MeV range. We calculate numerically the orbital angular momentum (OAM) of radiation produced by electrons with the energies $155÷2500$ MeV for the axial and planar channeling in the thin Si crystal. We obtain that the average OAM of CR in this case is approximately $1÷6?$ per photon with the photon energies about $1÷2$ MeV.