电阻测量实验中“远大于”条件的探讨

电阻的测量是高中物理教学中重要的电学实验,所涉及的实验方法较多,有伏安法、半偏法、替代法、欧姆表法等.其中伏安法、半偏法测电阻时,为减少系统误差,实验条件明确指出待测电阻的阻值必须满足远远大于某电阻的阻值或某电阻的阻值必须远远大于待测电阻的阻值.那么,到底多少才算得上"远远"呢?本文就来讨论这个问题.     

有限梯形电阻网络等效电阻的一个有效近似计算公式

利用n阶有限梯形电阻网络等效电阻值与无限梯形电阻网络的等效电阻值差的关系,给出n阶有限梯形电阻网络等效电阻的近似计算公式,数值计算表明所给近似计算公式对于计算有限梯形电阻网络等效电阻精确程度较高.     

三角形分形网络电阻上的电流分布

中点三角形和相似缩小正三角形的无限叠代,形成三角形电阻分形网络.自相似性要求节点上电流分配和比例系数不变.利用基尔霍夫定律,得到了这些系数的值.利用电阻电路的线性关系,得到了分形网络节点之间的等效电阻.     

放大系统在惠斯通电桥灵敏度研究中的应用

基于惠斯通电桥原理,在电位比较的基础上,加入了放大系统,通过调节放大系统的电阻,得出了在该模型下且在一定范围内,惠斯通电桥灵敏度具有一定的可调性,并发现在该模型下与待测电阻同路的电阻阻值与待测电阻阻值越接近越能获得高灵敏度,同时给出了此模型最佳适用条件。     

分数阻值的电阻化简问题

给出m n个阻值为1的电阻, 可以组成阻值为分数阻值m n 的电阻, 本文给出了一种将它化简, 以使所用 的电阻个数最少, 阻值仍为m n 的方法     

数字实验平台在物理探究课中的应用——焦耳定律探究实例

采用自制加热装置,借助温度传感器,定性地研究焦耳定律,证明了电阻的阻值越大,电流越大,加热时间越长,电阻产生的热量越多.实验容易操作,原理简明科学.     

用图像分析限流和分压接法中滑动变阻器的选取

借助Ux-Rap图像分析得出滑动变阻器的选取原则:控制电路采用限流接法时,要求滑动变阻器的最大阻值与被测电阻的阻值接近,即接近为原则;控制电路采用分压式接法时,滑动变阻器的最大阻值应远小于被测电阻的阻值,故在分压接法中,应选择阻值较小而额定电流较大的滑动变阻器.     

器物理原理演示教学仪器的研制

介绍了一种采用应变片、铂电阻、光敏电阻、磁敏电阻四种电阻型传感器来测量压力、温度、照度、磁场的物理演示教学仪器,可以定量地演示出压力和应变片电阻值、温度和铂电阻阻值、照度和光敏电阻阻值、磁场强度和磁敏电阻阻值之间的关系及给出电阻阻值与对应的物理量之间的曲线。介绍了演示仪器的检测原理和结构,该仪器用于本科生教学,可以使学生将物理学理论与工程实际应用有机结合起来,了解不同属性外场,引起电阻值的变化。拓展出形变、照度、温度、磁场检测等在工程技术中的应用。     

多层膜巨磁电阻特性及电流最佳测量

测量了不同方向外磁场和温度下多层膜巨磁电阻的磁阻特性,给出了巨磁电阻模拟传感器用于电流测量的最佳磁偏置.结果表明:外磁场强度相同但方向不同,对巨磁电阻的作用效果不同,巨磁电阻饱和时,阻值与外磁场方向无关.温度不同,巨磁电阻的阻值不同,磁电阻变化率也有改变.     

由一道电学实验题引发的思考

在探究电流跟电阻关系的实验中,必须控制导体两端的电压不变。当定值电阻的阻值变大或变小时,滑动变阻器的阻值应如何变化？滑动变阻器阻值的变化与定值电阻阻值的变化有什么定量关系？     

规则联接的多边形电阻网络的等效电阻研究

规则联接的多边形电阻网络可以简化为两部分相同的电阻网络的并联,将其中一部分变换为梯形电阻网络,针对奇数边形和偶数边形对应的梯形网络不同,经过相应的变换得到了规则联接的多边形电阻网络的表达式,这一结论也适用于规则联接的多边形电容网络.     

用电阻定义式求特殊电容器直流电阻

在电子线路工程及其教学过程中,都需要对电容器的直流电阻进行计算.然而,对一些特殊形状的电容器的直流电阻计算,普遍采用的电流密度法是比较麻烦的.本文根据电阻定义式,结合电阻的串联和并联的简洁关系,简单明了地对球冠形电容器、柱冠形电容器和正多棱柱形电容器等的直流电阻进行了计算,并给出相应的定量表达式.     

Mechanism of resistance distribution properties in oxide-based resistance switching nanodevice

Although oxide-based resistive switching memory (OxRAM) is one of the strong next-generation high-capacity memory candidates, it has an unresolved problem that the higher the resistance levels, the larger the cycle-to-cycle resistance variabilities to be operated in multi-resistance level mode. In this paper, we develop a simple theory from the operating principles of OxRAMs that excellently matches with experiments both qualitatively and quantitatively. From the theory, we can finally understand the fundamental capabilities of multi-resistance level operation of OxRAMs, and how to improve the switching properties within that.     

低温下固体接触热阻与接触电阻的实验研究

在低温工程中,两个接触固体之间存在着接触热阻与接触电阻,将对低温实验中热量及电流的传输产生显著的影响,是进行低温下物性研究的关键。自行研制了一套可同步实现固体接触热阻和接触电阻的测量装置,该系统具有较高的精度,可实现外界力、温度等对接触热阻的测量,同时具备接触电阻的实时测量功能。在此基础上,开展了外界压力、温度、电流对接触热阻和接触电阻的实验研究。实验结果显示:随着压力的增大,接触热阻与接触电阻随之减小;低温下,随着温度的增大接触热阻与接触电阻增大,接触电阻增大的速率要比接触热阻快。温度平衡时,20mA范围内的电流变化对接触电阻的影响显著,对接触热阻影响非常小。当界面温度达到室温后,首次观测到接触热阻和接触电阻会随着温度的增大而减小。     

对比式液体电阻演示器

现行教材中关于电阻大小与导体的材料、长度、横截面积、温度有关的实验只是用固态(金属)材料做实验得出结论,对于液体是否也符合该规律, 教材未做详尽说明. 为此,利用注射器等材料制作了对比式液体电阻演示器, 该演示装置可探究柱状液体的电阻与液体成分、长度、横截面积、温度的关系.     

Low-temperature resistance of DNA-templated nanowires

We present low-temperature measurements of the electrical conductivity of metallic nanowires assembled on single DNA molecules by chemical deposition of a thin continuous palladium film. The investigated nanowires exhibit ohmic transport behaviour at room temperature. At low temperature we observe an increase of resistance with decreasing temperature that follows a logarithmic dependence. This behaviour can be described with quantum effects in a disordered metallic film. Received: 4 October 2001 / Accepted: 12 December 2001 / Published online: 20 March 2002     

Anisotropy of domain wall resistance

The resistive effect of domain walls in FePd films with perpendicular anisotropy was studied experimentally as a function of field and temperature. The films were grown directly on MgO substrates, which induces an unusual virgin magnetic configuration composed of 60 nm wide parallel stripe domains. This allowed us to carry out the first measurements of the anisotropy of domain wall resistivity in the two configurations of current perpendicular and parallel to the walls. At 18 K, we find 8.2% and 1.3% for the domain wall magnetoresistance normalized to the wall width (8 nm) in these two respective configurations. These values are consistent with the predictions of Levy and Zhang.     

Peltier-effect-induced correction to ohmic resistance

The standard ohmic measurements by means of two extra leads contain an additional thermal correction to resistance. The current results in heating (cooling) at the first (second) sample contact because of the Peltier effect. The contact temperatures are different. The measured voltage is the sum of the ohmic voltage swing and the Peltier-effect-induced thermoelectromotive force that is linear in the current. As a result, the thermal correction to the resistance measured exists as I→0. The correction could be comparable with the ohmic resistance. Above some critical frequency depending on thermal inertial effects, the thermal correction disappears.     

Contactless method of resistance measurement

A contactless method to measure the resistance is suggested that allows one to calculate the distribution of the resistance over the sample with a step of 0.1 mm in the resistance range 10⁷−10¹³ Ω (polyethylene, silicon dioxide, and other high-resistivity materials). In the course of measurement, the sample must be on a nonconductive substrate. The system is charged (or discharged) with a needlelike electrizer, and a charge (or discharge) current pulse is detected. The amplitude of the pulse grows with conductivity of the sample and therefore can be used to measure its resistance. Using this method, one can quickly determine, e.g., the photoconductivity of the material and temperature dependence of the resistivity or estimate how, say, the air humidity or a nearby radioactive source influences the conductivity. With the resistance of the sample known, one can find, for example, the humidity of the environment, illuminance, or radioactive radiation intensity.