Subsonic electrically quasi-neutralweakly-ionized gas flow past a spherical probe

The electric characteristics of a sphere located in a flow of viscous, electrically quasi-neutral weakly-ionized gas containing electrons and monovalent ions are investigated theoretically and numerically. As in the majority of applications, the electrogasdynamic (EGD) interaction parameter is assumed to be small. This makes it possible to solve the gasdynamic and electric equations successively. The spherical surface is assumed to be conducting and heat-insulated. At low free-stream Mach numbers the gas temperature is almost constant in the region of flow past the sphere. This makes it possible to use the model of a viscous incompressible medium. The flow past a sphere is analyzed for gasdynamic Reynolds numbers varying over the interval 0 ≤ Re ≤ 1000. The electrodynamic equations in which the convection and diffusion of the electrons and ions and their electrical drift are taken into account are reduced to three elliptic equations for the electron and ion concentrations and the electric potential. A constant potential is assigned on the boundary of the computation region simulating infinity. The entire problem is simulated numerically using specially constructed grids. The charged-component, potential, and electric current fields are determined and the volt-ampere characteristics of the sphere are constructed for various gas velocities. The results obtained generalize the available data on the voltampere characteristics of a sphere (probe) in a weakly-ionized medium at rest.     

用示波器研究晶体管特性曲线

本推出一种在示波器上研究晶体管特性曲线的新方法。     

新型PbO_2电极在测定COD中的初步应用

以新型PbO2 电极作为工作电极组成三电极工作系统 .以恒电位伏安法的原理测定电流值 ,并通过增大电位气泡更新法对电极再生 ,来阻止电极表面被污染 ,保证了测量的重现性 .通过对葡萄糖标准溶液与邻苯二甲酸氢钾溶液COD值的测定 ,表明此法有好的运用价值     

发光二极管基本物理特性测量及研究——介绍一个与节能有关的研究性物理实验

介绍一个与节能有关的研究性物理实验,该实验对发光二极管的基本物理特性进行了研究,可使学生深入理解发光二极管的发光原理、特性及其测量方法.     

PN结正向伏安特性曲线随温度的变化

介绍了在不同温度下，PN结正向伏安特性曲线的自动测量方法。讨论了PN结伏安特性与温度的关系．由于正向结电压小于内建电势差，温度升高或正向结电压增加，正向结电流将增大，温度升高反向结电流也相应增加．当温度趋向OK时。正向结电压趋向内建电势差。     

光电效应伏安特性实验改进研究

光电效应实验及理论解释,为量子理论的建立奠定了基础,在光电效应伏安特性实验中,如何有效减少实验影响因素,提高测量结果的精确度,成为光电效应伏安特性实验改进的一个关键点。本从光电效应实验测量的伏安曲线出发,分析理论与实验结果上的差异,提出了影响实验结果的因素以及相应的实验操作办法,为光电效应伏安特性实验的改进,获得更加精确的实验数据以及光电效应实验的应用奠定了基础。     

稳压管伏安特性测量中电表的正确接法

研究电流表接法对稳压二极管伏安特性测量结果的影响。理论分析和实验研究表明,测量稳压二极管的伏安特性时,在稳压管的正向死区和反向截止区电流表应该内接,在其正向导通区和反向击穿区电流表应该外接。这样,只要电流表内阻足够小且电压表内阻足够大,测量系统误差就远小于1%。     

稳压二极管的非线性伏安特性研究

用FD-UI-A非线性元件伏安特性实验仪测量了稳压二极管的正向和反向伏安特性,研究结果表明,稳压二极管的正向和反向伏安特性都呈现出非线性,但其正向和反向的lnI-Ud呈良好的线性关系,其斜率反映了二极管材料的导电特性.     

一种实用的实验室电源的设计

介绍了一种实用的物理实验专用线性可调稳压直流电源。该电源由可调三端稳压、可调基准电压、限流电路等构成,可提供0～12 V连续可调电压,输出电流限制在100 mA,适用于大学物理实验中二极管伏安特性测量、三用电表的设计与制作等设计性实验,起到对实验器件和仪表的保护作用。