如何看待失重和超重的问题

宇宙飞行员的失重是不是由于他所在的地区重力加速度为0?宇宙飞行员在飞出去的时候,重力加速度愈来愈小,为什么又会超重呢?这些问题具有一定普遍性,必须从理论上进行回答。因此,我想在这里谈谈自己对这个问题的看法。为了使问题简化,我们作如下两个假设: 1.认为地球是一个半径为6400公里密度均匀的球体,这样就保证了地球的质心与其几     

关于狭义相对论同时性问题

长期以来,在有关狭义相对论的讨论中比较重要的一个基本问题,就是光速各向同性的假设是否为实验证实和是否能够用实验证实的问题.为了讨论这个问题,我们先说明如何测量一个质点沿某给定方向的运动速度(简称单向速度), 要确定一质点的单向速度,就要确定该质点通过给定距离AB所花费的时间t_(AB),这就需要使用两只钟计时,一只钟位于A点,另一只位于B点.但是,要使这两只钟的读数之差t_B一t_A“确实”代表t_(AB),就必须事先用某种手段使它们对准.用什么手段来校准不同地点的钟呢?这个问题就是所谓的不同地点的同时性问题.早在1905年,爱因斯坦…     

关于《物理问题的物理解法》的几点讨论

笔者觉得《物理通报》2009年第8期的“短文荟萃”栏目中《物理问题的“物理解法”》一文中一些内容的阐述方法和科学性值得商讨;其中反映的一些问题,在中学物理教育中存在一定的普遍性．现讨论如下．     

热力学第二定律和热寂说的起源与发展

热力学第二定律是热力学三定律中最重要的,也是一百多年来引起争论最多的一个热力学基本定律．由这个定律推广到宇宙范围而产生的热寂说,更是科学界和哲学界一直关注并引起激烈争论的重大问题．这个定律从二热体或二物质系之间热量传递的方向性,阐述了自然界的一个基本规律．但是,它的意义却更为深远,关系到包括生命物质在内的万物生长、发展和消亡的普遍性规律性问题．热功可逆转化和守恒只是这个定律在可逆过程情况下的?...     

再论船渡河问题

贵刊2012年第3期的短文荟萃中"现行船渡河问题分析的逻辑缺陷"一文解答了学生关于船渡河时水速大于船速情况下要使实际位移最短问题中的疑问.笔者认为,原文作者似乎把简单问题复杂化     

对滑动摩擦力做功问题的分析

计算滑动摩擦力做功的问题在中学和大学物理教学中经常出现,在一些物理书刊上也经常出现.这里,先讲一下计算滑动摩擦力做功的传统方法及其存在的问题,然后谈对这个问题的看法.     

怎样使学生获得透彻、深刻和巩固的基本知识

我认为提高教学质量的最关键最基本的问题是使学生获得透彻、深刻和巩固的基本知识,关于这个问题,我考虑得还很不成熟,但是愿意提出自已的看法来与大家共同研究。我们要使学生巩固掌握知识,说一个比方,如果知识可以按个数计算,有一位教师教给学生十个知识,     

电离辐射在半导体器件中引起的光电流的数值模拟

电离辐射在半导体中引起光电流问题是半导体器件辐照效应研究中的一个带普遍性的课题，首先建立描述半导体中光电流过程的普遍性的物理模型，而后模拟一个实际ｐｎ结器件的光电流响应，给出模拟结果。     

关于提高仪器总体设计水平的问题

光学仪器的总体设计是正在形成的一门课题。本文提出这方面的几个根本性问题:(1)运用研究;(2)指标分析;(3)总体参数确定;(4)各分系统任务的平衡和指标分配。在光学仪器中,光学、机械、电学等各个环节在信息的传递和变换过程中的规律具有共同性,可以用共同的数学方式来处理。采用系统工程和信息论的概念讨论这些带普遍性的问题,有助于本课题的深入。本文还探讨了为将来用计算机进行总体设计所应准备的条件:基础实验数据和数学模型问题。     

关于大学物理与中学物理衔接问题的教学研究探讨

中学物理与大学物理如何实现有效的衔接,是每位大学物理教师必须思考的普遍性问题。中学物理实行模块化教学,即分为必修模块和选修模块,大学物理相比较更具系统性,尤其是针对理工科学生的教学内容更为全面和深入。二者在教学内容、教学方式和思维方法上的差异导致大学生在学习过程中遇到很多困难,影响了大学物理的教学质量。作者通过分析学生由中学物理到大学物理过渡学习中出现的问题,提出必须要树立一种正确的学习理念,改变大学物理学习过程中的一些错误观念,从基础入手解决大学物理和中学物理课程之间的衔接。结合一些物理教学知识点,总结出实现中学物理到大学物理良好过渡的几点体会。     

Parametric excitation of hybrid mode in magnetised piezoelectric semiconductors

Using the hydrodynamic model of homogeneous plasma, the parametric decay of a laser beam into an acoustic wave and another electromagnetic wave has been studied in heavily dopedn-type piezoelectric semiconductors in the presence of a transverse magnetostatic field. This decay process results in the parametric excitation of the hybrid mode. The threshold electric field necessary for the onset of instability equals to zero. The magnetostatic field couples the acoustic and the electromagnetic waves and in its absence the instability disappears. The growth rate increases with the square of the magnetic field.     

Determination of wave fields from perturbed particle orbits

The linear problem of determining wave electric fields from measured perturbed particle distribution is considered. Previous work is extended to consider the case of arbitrary wave structure transverse to the magnetic field. The calculations are limited to electrostatic waves, although the ideas extend naturally to electromagnetic waves, and are illustrated in the one-dimensional case using data taken by laser-induced fluorescence     

电、磁场作用于扁球边界面上的力矩

本文研究电、磁场作用于扁球导体、磁导体上的力矩。根据基本解答和把体积力公式运用于扁球体面上后(包括平面上有半扁球形突面的边界问题〕,得出静电问题的较为普遍的解式。又由于静电、静磁张力公式的简单对应关系存在,故很容易把所得到的公式直接推广到对应的静磁问题上去,最后根据所得的解式,我们得到了若干有益的结论。     

平面横电磁波模的初值问题

经典理论所描述的电场和磁场处处同相的平面电磁波模并不存在.Maxwell方程组的解依赖于 电磁场的初始值或边界条件,根据不同的初始条件解得的平面电磁波模是不同的.结果表明 ,平面电磁波是横波,在不同的位置,由变化的电场激发的磁场或由变化的磁场激发的电场 振幅不同,电场与磁场的相位差也不同. 关键词： Maxwell方程组 最优微分方程 初始条件 平面电磁波     

Spontaneous electromagnetic emission from a strongly localized plasma flow

Laboratory observations of electromagnetic ion-cyclotron waves generated by a localized transverse dc electric field are reported. Experiments indicate that these waves result from a strong E×B flow inhomogeneity in a mildly collisional plasma with subcritical magnetic field-aligned current. The wave amplitude scales with the magnitude of the applied radial dc electric field. The electromagnetic signatures become stronger with increasing plasma β, and the radial extent of the power is larger than that of the electrostatic counterpart. Near-Earth space weather implications of the results are discussed.     

电磁偏置各向异性石墨烯界面的传播矩阵

基于电磁场边界条件和相位匹配,推导出电、磁偏置下呈各向异性的石墨烯导电界面的传播矩阵,并进一步给出各向异性石墨烯界面的反透射系数解析解;该传播矩阵耦合了基本的横电波和横磁波极化,并包括偏置电、磁场的影响.将跨石墨烯界面传播矩阵嵌入各向同性分层介质传播矩阵,获得的新传播矩阵可用于解析分析平面电磁波以任意角度入射含各向异性...     

Inverse problem of relativistic mechanics for a test charge in an external static field

We consider the motion of an electrically charged test particle in static spacetime when it is necessary to reconstruct the electromagnetic field tensor. The problem is solved for the two special cases when the electromagnetic field reduces to an electrostatic field or a magnetostatic one. It is shown that the electrostatic field can be determined within a single arbitrary function, and the magnetostatic field within two such functions.Translated from Izvestiya Vysskikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 67–70, February, 1982.     

Slow electromagneticw waves in tangentially magnetized ferromagnetic films

Dispersion and energy characteristics of slow volume electromagnetic waves in tangentially magnetized ferromagnetic films are computed in a rigorous manner. For a wave that experiences anomalous dispersion and propagates with the external magnetostatic field, distinguishing features of the energy-flux velocity and the ratio of the electric to the magnetic energy density as functions of the wave number are noted. A marked contrast between these results and those obtained within the magnetostatic approximation is revealed for a wide range of wave numbers.     

A slow wave with the structure of an electromagnetic wave in piezoelectric and magnetostrictive media

The propagation of elastic waves in piezoelectric and magnetostrictive materials is considered theoretically. It is shown that an elastic wave in a piezoelectric can create not only a longitudinal electric field parallel to the wave normal (longitudinal piezoactivity) but also a transverse field of electric induction (transverse piezoactivity). The presence of a transverse induction field leads to the appearance of a magnetic field perpendicular to the direction of the wave normal and to the induction vector; therefore, the transverse-piezoactive wave is accompanied by a transverse wave having the structure of an electromagnetic wave and propagating with the speed of sound. Transverse-magnetostrictive elastic waves in magnetostrictive dielectrics are accompanied by a similar wave.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 32–36, October, 1976.     

Relativistic nonlinear waves in a magnetised plasma

Relativistic propagation of a nonlinearly-coupled circularly-polarised electromagnetic wave and a Langmuir wave along the applied magnetic field is considered. Analytical solutions are given or are indicated for some special cases like purely transverse waves and purely longitudinal waves. In the presence of an applied magnetic field, the incident circularly polarised electromagnetic wave is found to propagate further into denser regions of the plasma — a result which is in accord with the so-called inverse Faraday effect. Finally, we shall consider general coupled transverse and longitudinal waves for which we give an approximate solution. We investigate whether this system of coupled waves exhibits any internal resonances and consequent energy exchange between them.