电磁驱动与电磁阻尼演示仪原理探究

将演示仪电磁驱动和电磁阻尼二者巧妙地结合起来,并利用单片机测量及数字化显示技术,更好地演示了电和磁这两种特殊物质抽象的物理本质和物理原理.     

电磁振荡演示仪设计的理论依据

电磁振荡演示仪是用电流计来显示振荡电流的,其基本电路如图1所示。图中E是电源电动势,C是电容器的电容,L是振荡线圈的自感系数,R_L是振荡线圈的电阻,R_(?)是电流计的内阻。电流计的线圈自感系数与L相比甚小,略而不计。     

对“ 涡流电磁驱动原理演示仪的制作”的改进

随着科技的发展, 新材料、 新技术为教具制作提供了更广阔的空间, 使原本笨重的教具制作可以更简 单化、 轻便化, 而且效果更理想. 不仅教师能够制作, 学生也可动手操作, 边制作边进行实验探究. 既增强了学生的 动手能力, 又能提高学生的科学素养. 现就电磁驱动和电磁制动提供一个改进案例, 供同行们参考     

涡电流及其机械阻尼效应演示

本文对涡电流的机械阻尼效应作一受力分析并设计一个好的演示实验。     

电磁阻尼实验

1 原理 通过本实验能动态分析楞次定律中能量的转化.根据楞次定律,感应电流的效果总是反抗引起感应电流的原因,它是能量守恒和转化定律的必然结果.当把磁棒插入线圈或从线圈中拔出时,都必须克服斥力或引力做机械功,实际上正是这部分机械功转化成感应电流所释放的焦耳热,正是这种反抗才实现了能量的转化.     

新型楞次定律闪光演示仪

楞次定律表述感应电流的方向十分抽象, 规律十分隐蔽, 直接通过教材里的“ 螺线管四组实验”很难会 想到利用“ 中介” — — — 感应电流的磁场来揭示规律, 并且实验中没能将“ 中介”方向直观地显示出来, 这对于学生理 解感应电流的磁场与引起感应电流的磁通量变化之间的关系带来认知负荷的超标, 从而难以发现或者描述其中的 规律. 为此, 笔者特别制作了教具 — — — 新型楞次定律闪光演示仪, 通过延长发光二极管闪光时间, 引发学生的视觉 享受, 直观地展现“ 增反减同”的规律, 迅速突破“ 表述”的难点, 同时极大提高了学生对电磁感应现象探究的乐趣     

自制洛兹力投影演示仪

电磁现象的演示,对提高教学效果有重要意义.我们自制了洛伦兹力投影演示仪,并在教学实践中不断改进、应用,收到很好效果.现介绍如下.     

涡电流电磁感应演示仪的设计

以一个新的角度--涡电流效应演示电磁感应现象.演示仪器引入气垫导轨,由悬挂的钕铁硼永磁铁与铝板小车在接近无外界阻力的状态下相互作用来演示动生电动势现象;由高频交流电磁铁加热铝板小车或点亮接有线圈的小灯泡演示感生电动势现象.     

电磁阻尼落体运动实验仪研究

设计了电磁阻尼落体实验仪,可以定量研究受电磁阻尼的落体运动过程,在不同的阻尼条件下验证速度和路程公式,并计算出阻尼系数.     

用钕铁硼制作阻尼振动、受迫振动及共振演示仪

利用稀土永磁性材料钕铁硼(Nd-Fe-B)设计制作出了新型阻尼振动、受迫振动及共振演示仪.该演示仪器可演示阻尼振动的3种状态(欠阻尼状态、临界阻尼状态、过阻尼状态)、受迫振动及共振现象.     

一种新的角动量守恒演示实验仪

介绍了新研制成功的一种物理演示实验仪,它是以进动过程中突然除去进动的原因而使进动中止的方式来演示角动量守恒的．实验仪结构简单,操作方便,反映的物理原理深刻．     

A new solvent suppression method via radiation damping effect

Radiation damping effects induced by the dominated solvent in a solution sample can be applied to suppress the solvent signal. The precession pathway and rate back to equilibrium state between solute and solvent spins are different under radiation damping. In this paper, a series of pulse sequences using radiation damping were designed for the solvent suppression in nuclear magnetic resonance (NMR) spectroscopy. Compared to the WATERGATE method, the solute signals adjacent to the solvent would not be influenced by using the radiation damping method. The one-dimensional (1D) ¹H NMR, two-dimensional (2D) gCOSY, and J-resolved experimental results show the practicability of solvent suppression via radiation damping effects in 1D and 2D NMR spectroscopy.     

Measurements, characteristics, and origin of new electromagnetic interference on magnetocardiographic measurements

In order to eliminate the influence of the large-amplitude magnetic field noise that has complicated magnetocardio-graphic studies since October 2009, we have performed high-accuracy measurement of the environmental magnetic field noise in the vicinity of Beijing Subway Line 4 using a three-component height T c radio frequency (rf) superconducting quantum interference device (SQUID). By analysing the spatial form and other characteristics of the time and the frequency domains and by calculating the circumferential magnetic field distribution based on a duel-end feeding system model, we reach the following conclusions: (i) the main source of magnetic field noise is the magnetic field generated by the subway trains, and (ii) the magnetic field interference results mainly from the imbalance between traction current and return rail current that is caused by the leakage current.     

一种新时域交替隐式差分算法在散射问题中的应用

提出一种新时域交替隐式有限差分(ADI-FDTD)算法格式. 传统ADI-FDTD算法的 场量步进方程涉及周围若干网格的较多场量，导致两个区域的步进方程处理较困难：一个是 邻近完全匹配层(PML)和散射场交界区，另一个是邻近连接边界区. 特别是后者，考虑入射 波影响需对场量所在区域判断，根据不同情况对原有方程进行修正，一维和二维散射问题 相对简单，可三维问题修正式有数十种之多而几乎无法完成. 本方法基于分裂场形式的ADI- FDTD技术，使得散射场区和PML吸收层区的表达形式完全一致，从而忽略两者差别.另 关键词： 时域交替隐式有限差分算法 电磁散射     

A possible mechanism of current in medium under electromagnetic wave

In this paper a possible mechanism of current in medium is presented. Comparison between this current and the magnetization current was made. Expression for this current was derived. This work is helpful to understanding the interaction between medium and electromagnetic wave.     

A damping boundary condition for atomistic-continuum coupling

The minimization of spurious wave reflection is a challenge in multiscale coupling due to the difference of spatial resolution between atomistic and continuum regions. In this study, a new damping condition is presented for eliminating spurious wave reflection at the interface between atomistic and continuum regions. This damping method starts by a coarse–fine decomposition of the atomic velocity based on the bridging scale method. The fine scale velocity of the atoms in the damping region is reduced by applying nonlinear damping coefficients. The effectiveness of this damping method is verified by one-and two-dimensional simulations.     

随机耦合模型中损耗因子的分析与获取

随机耦合模型(RCM)是研究电磁脉冲干扰下波混沌系统中感应电压统计预测的新方法,其中波混沌腔体损耗因子的获取是这种方法使用的关键。从随机耦合模型理论出发,分析了损耗因子对腔体阻抗随频率变化特性的影响,探讨了不同损耗因子下归一化阻抗矩阵的统计特性,提出了使用腔体散射阻抗与辐射阻抗的比值作对照,以快速获取腔体损耗因子的新方法。