利用洛伦兹力演示器探究带电粒子在电场及磁场中的运动

洛伦兹力是磁场对运动电荷的作用力,比较抽象,学生无法直接观察,针对该问题,采用了J2433-1型洛伦兹力演示器来探究带电粒子在电场和磁场中的运动,并测量了电子的比荷,该方法可在三维空间观察电子运动的径迹,通过宏观现象认识了微观本质.     

验证感生电场存在的实验

针对磁场变化时激发产生的感生电场很难演示的问题,设计了演示感生电场存在的实验. 该实验将不同功能的仪器组合起来使用,通过亥姆霍兹线圈的交变磁场对带电粒子的作用效果,直观说明感生电场的存在.     

在感生电场中电势是无意义的

在教学过程中,发现有的书籍在感生电场部分编入了一些有概念性错误的习题和例题。例如:F.W.Sears等著(恽瑛等译)的《大学物理学》①,张静汇编的中央广播电视大学《教学参考资料》②,王发伯等编的《普通物理典型题解》③,都编入了一些在感生电场中求两点电势差的问题,据我所见,在各校的测验和考试题中犯同类错误者也不少。因此,深刻理解电势引入的条件和感生电场的特点是十分必要的。 成生电场是变化的磁场激发的电场。具体又分两种情形:由于导体在磁场中切割磁感应线,而在导体中产生的成生电场;以及当穿过任一回路(不管有无导体回路存在)…     

动生电动势和感生电动势的特殊相对论关系

电磁感应电动势分动生电动势和感生电动势两种。当闭合线圈与某一稳定磁场作相对运动时,在线圈中会感应出电动势。与磁场相对静止的观察者认为,这电动势是动生电动势;与线圈相对静止的观察者则认为,这电动势是感生电动势。这样的动生电动势和感生电动势在数值上是否相等?如果我们另选一个参考系,使得磁场和线圈都相对于它运动,那末,在线圈中将同时具有动生电动势和感生电动势,总电动势的数值与什么有关?动生电动势和感生电动势是相对的还是独立的?这些问题将在下面分别加以研究。 一、设坐标系S相对于磁体静止,任意形状的闭合线圈在磁场中…     

截面异形的轴向变化磁场产生的感生电场

介绍一种计算感生电场的数值方法,它既可用于计算柱形分布均匀变化磁场所产生的感生电场,也可计算分布在任意界面上的变化磁场所产生的感生电场,并给出了一些计算实例．     

应该重视感生（涡旋）电场的方向性教学

感生电场的计算在大学物理教科书中,一般都是以具有轴对称性磁场变化为特例.在那里,感生电场的方向是不证自明的,真的是这样吗？本文力图说明,对称性并不能取代方向性的说明,方向性问题严格说来需要解边值条件下的微分方程,但在大学物理教学层面上可以有简单的办法处理.     

浅议安培力与洛伦兹力

关于安培力与洛伦兹力,现行中专物理教材提到:“(磁场)作用在通电导线上的安培力,只不过是作用在运动电荷上的力(洛伦兹力)的宏观表现”.高级中学课本《物理》甲种本上说“安培力可以看成是这一段通电导体中所有定向运动的电荷所受洛伦兹力的总和”.那么定向运动的电子所受到的洛伦兹力是怎样成为载流导体的安培力的?本文就此问题谈谈自己的一点看法. 1 磁场中静止的载流导体如图所示的载流导体,电流强度为I,处在方向向左的匀强磁场B中,因为载流导体中每个定向运动的电子,都要受到一个洛伦兹力f_L的作用,其大小F_L=evB,方向沿 Z,这导致导体A侧出现负电荷的堆积,B侧出现正电荷的堆积,结果在载流导体上下两侧产生一个U_(BA)的电位差,形成一个沿 Z的横向电场E,故每个定向运动的电子受到一个沿—Z     

感生电场作用下的电流变化问题的思考与分析

“电磁感应”一章的第5节内容有这么一句话,“英国物理学家麦克斯韦认为,磁场变化时会在空间激发一种电场,这种电场与静电场不同,它不是由电荷产生的,我们把它叫做感生电场.如果此刻空间存在闭合导体,导体中的自由电荷就会在感生电场的作用下定向运动,形成电流.”这句话引出了自己的一个思考,感生电场是闭合的,电荷是不是就不断地加速下去了呢,一圈又一圈,直至光速?当时很随意的一个想法,后来随着思考的深入有了更进一步的认识,下面就这个问题做一些展开.     

展示相对性原理和电磁场相对性的一个佳例

以条形磁铁与导体圆环相对运动为例,依据导体圆环产生感应电流这一事实,首先讨论了条形磁铁参考系和导体圆环参考系下电场和磁场的不同.并在条形磁铁参考系下,从产生动生电动势的物理本质洛伦兹力出发,导出了法拉第电磁感应定律.然后,在导体圆环参考系下,由相对性原理直接给出了感生电场性质的数学表述,并深入讨论了电场和磁场的联系.最后,给出了爱因斯坦和费曼对该问题的不同思考并进行了简单分析.     

洛伦兹力演示仪

为了使学生深入了解洛伦兹力,设计制作了喷泉洛伦兹力演示仪.该演示仪将电场和磁场按照一定方向放置,使离子溶液受到向上的洛伦兹力,在洛伦兹力作用下,溶液向上运动,进而形成了喷泉.     

Electric field and Lorentz force contribution to atmospheric vortex phenomena

The physics that initiate and sustain tornados and dust devils is still under investigation. Forces that operate throughout a wide range of scales and could contribute to atmospheric vortex phenomena are the Lorentz force and the force of electric fields. The Lorentz force results in a circular motion of charged particles in a magnetic field. An electric field will pull or repel a charged particle in the direction of the field. This paper will demonstrate that the Lorentz force and the force of electric fields, acting on charged particles that exist in atmospheric vortex phenomena, plausibly contribute to the set of physics that will explain tornados and other atmospheric vortex phenomena.     

洛伦兹力公式是怎样给出的

在电子尚未发现,并无任何实验证据的1892年,洛伦兹力公式是怎样给出的?回顾了电磁学历史上超距作用和近距作用观点的长期论争以及"什么是电"的长期论争后指出,洛伦兹力公式是场观点和"电就是带电粒子"相结合的产物.一切磁作用力都应归结为磁场对运动带电粒子的作用力--洛伦兹力.     

经典洛伦兹磁力和广义洛伦兹磁力解释电子感应加速器的本质

介绍了虚构的法拉第定律与电子感应加速器不合理,用完整洛伦兹磁力解释电子感应加速器合理有效。     

Effect of vacuum fluctuations on the motion of an electron in the magnetic field of an accelerator

The Langevin form of the quasiclassical approximation for an electron in a magnetic field is used to find the most general expression in the first order in fa for the vacuum-fluctuation Lorentz force. It is shown that besides the mechanism of excitation of fluctuation oscillations due to the recoil momentum there also exists a transverse (relative to the photon wave vector) fluctuation force due to the incomplete compensation of the electric force and the transverse component of the magnetic Lorentz force.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 42–46, March, 1981.     

Lorentz effect imaging

This paper presents a method that can detect minute electrical activity in a strong magnetic field. It uses displacement encoding to detect small spatial displacement induced by Lorentz force on the conducting materials, hence the term Lorentz effect imaging (LEI). With increased sensitivity from improved hardware capabilities or signal averaging, this technique may be used to detect spatial displacements induced by small currents comparable to neuronal electrical current. The initial results using the LEI technique may provide insight in assessing the feasibility of using MRI to non-invasively detect the neuronal electrical activities.     

Spin transverse force on spin current in an electric field

As a relativistic quantum mechanical effect, it is shown that the electron field exerts a transverse force on an electron spin 1/2 only if the electron is moving. The spin force, analogue to the Lorentz for an electron charge in a magnetic field, is perpendicular to the electric field and the spin current whose spin polarization is projected along the electric field. This spin-dependent force can be used to understand the Zitterbewegung of the electron wave packet with spin-orbit coupling and is relevant to the generation of the charge Hall effect driven by the spin current in semiconductors.     

磁单极与磁洛伦兹力

概述了磁单极概念的历史发展,从洛伦兹变换出发,利用电磁场张量和四维力的协变性以及电荷相对论不变,直接证明了运动磁单极受磁洛伦兹力,建议了一个磁洛伦兹力的验证方案,并用磁洛伦兹力公式导出狄拉克电荷量子化条件．证明了磁洛伦兹力公式具有与库仑定律相同的精确度．     

激光驻波中运动电子的谐波自发辐射

 采用单电子模型分析了电子在线极化激光驻波中的动力学及谐波自发辐射谱,数值计算了电子在驻波中的运动情况及辐射谱。结果表明:电子在波节和波腹处入射后,其辐射谱出现不同的特征;电子在波节处垂直磁场入射后,在洛伦兹力作用下快速振动并向前运动,其向后辐射的光谱发生红移,向前辐射的光谱发生蓝移,谱线出现展宽;当激光强度或者电子初始能量增大时,这些效应更加突出,以至于产生更高阶谐波,形成连续谱;而电子在波腹处以平行电场的方向入射后,仅在电场作用下作直线运动,其自发辐射谱线没有发生移动和展宽。     

A current density conservative scheme for incompressible MHD flows at a low magnetic Reynolds number. Part II: On an arbitrary collocated mesh

A conservative formulation of the Lorentz force is given here for magnetohydrodynamic (MHD) flows at a low magnetic Reynolds number with the current density calculated based on Ohm’s law and the electrical potential formula. This conservative formula shows that the total momentum contributed from the Lorentz force is conservative when the applied magnetic field is constant. For the case with a non-constant applied magnetic field, the Lorentz force has been divided into two parts: a strong globally conservative part and a weak locally conservative part.The conservative formula has been employed to develop a conservative scheme for the calculation of the Lorentz force on an unstructured collocated mesh. Only the current density fluxes on the cell faces, which are calculated using a consistent scheme with good conservation, are needed for the calculation of the Lorentz force. Meanwhile, a conservative interpolation technique is designed to get the current density at the cell center from the current density fluxes on the cell faces. This conservative interpolation can keep the current density at the cell center conservative, which can be used to calculate the Lorentz force at the cell center with good accuracy. The Lorentz force calculated from the conservative current at the cell center is equivalent to the Lorentz force from the conservative formula when the applied magnetic field is constant, which can conserve the total momentum. We will further prove that the simple interpolation scheme used in the Part I [M.-J. Ni, R. Munipalli, N.B. Morley, P.Y. Huang, M. Abdou, A current density conservative scheme for MHD flows at a low magnetic Reynolds number. Part I. On a rectangular collocated grid system, Journal of Computational Physics, in press, doi:10.1016/j.jcp.2007.07.025] of this series of papers is conservative on a rectangular grid and can keep the total momentum conservative in a rectangular grid.     

相对论的协变场是虚构

基于洛伦兹电子论和洛伦兹磁力,否定法拉第定律和相对论电磁学,暨揭示广义洛伦兹磁力的科学研究之五:相对论的协变场是荒唐。本文基于洛伦兹电子论和洛伦兹磁力,论证表明:协变换出来的磁力线成为直线,它违背客观事实;协变换出来的环形电力线更荒唐;协变换出来的电磁场成为无穷大,广义洛伦兹磁力才是真谛;两电荷对撞时协变换出来的排斥力成为虚数,它违背客观事。