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1.
在《电磁转换》一章中“,磁场对电流的作用、电动机”这一节是一个重点,也是难点.要学好这部分内容,可以先从弄清“两个实验、三个方向、一台机器”出发,然后再作适当的应用来实现学习要求.一、两个实验(1)通电导体在磁场中受力运动的实验在学习奥斯特实验的基础上进行逆向思维后,再观看通电导体在磁场中受力运动的实验,对于通电导体在磁场中受力运动的印象会很深刻.在继续探究中,会自然而然地发现,这个力的方向跟磁场方向和电流方向有关系.可是,有一种特殊情况,即当通电导体中电流方向与磁感线方向平行时,通电导体不受磁场对它的作用力.从…  相似文献   

2.
本教学设计通过探究磁场对通电导体的作用,知道通电导体在磁场中受力的方向与电流方向和磁场方向有关,知道通电导体在磁场中受力的大小与电流大小和磁场强弱有关。通过探究磁场对通电线圈的作用,掌握电动机换向器的原理和作用。  相似文献   

3.
在做通电导体在磁场中受力运动的演示实验时,一般用铝导线作为通电导体,由于铝导线的直径小,实验的可见度低,不利于学生对实验的观察.为了增大实验的可见度,有利于学生观察通电导体在磁场中的运动情况,可制作一个空心导体.  相似文献   

4.
在现行的甚至以前的中学物理课本里,判定通电导体在磁场中受力的方向时用到左手定则,判定闭合回路的部分导体在磁场中作切刈磁力线运动产生的感生电流的方向时用到右手定则.这样,一个用到左手,一个用右手,有时容易混淆.我们可以来一个“精兵简政”,只用右手.恩格斯指出:“由于人的活动,就建立了因果观念的基础,这个观念是:一个运动是另一个运动的原因.”通电导体在磁场中受力作用时,导体在磁场中通电是原因,受到磁场的作用力是结果;闭合回路的部分导体在磁场中作切刈磁力线运动时,导体在磁场中运动是原因,产生感生电流是结果.两过程中都“以磁为媒介”.这样我们就可以只用右手,拇指表示原因,其余四指表示结果.我们的定则为:伸开右手,让拇指跟其余四指垂直,并且都跟手掌在同一平面内,使磁力线垂直穿过掌心.判定磁场对通电导体的作用力方向时,用拇指指向电流方向,则其余四指指向通电导体在导场中受力的方向;判定感生电流方向时,用拇指指向运动方向,则其余四指指向感生电流方向.如果我们把上述作为原因的量称为原因量,作为结果的量称为结  相似文献   

5.
张学斌 《物理教学》2010,(3):30-30,63
当通电导体与磁场方向垂直放置在磁场中时,它受到磁场力的大小F与电流的大小I成正比、与通电导体长度L成正比、还与磁场的强弱——磁感应强度B成正比。为了能通过探究手段得出上述规律,本人自制了磁场对通电导体作用探究仪,通过本人与同校物理教师的多次使用,教学效果非常好。下面就把该探究仪向大家介绍一下,望各位同行予以指正更新,以便更好地服务于教学。  相似文献   

6.
高中教材必修课本第二册第三章第三节中,通过通电导体在水平放置的蹄形磁铁磁场中左右摆动的演示实验说明:通电导体在磁场中要受到力的作用,并进一步实验说明了,电流强度及通电导体在磁场中长度  相似文献   

7.
当磁场与通电导体垂直或成一夹角时,磁场对通电导体的作用力,可通过演示实验给学生看。但当磁场与通电导体平行时,磁场对通电导体有没有作用力,通常教师讲得多,实验演示很少。因为,学校实验室没有较大的马蹄形磁铁,做实验不太方便。  相似文献   

8.
针对教材中"磁场对通电导体的作用"实验装置存在的问题,用强磁铁对磁场进行改进,用吸管和锡箔对导体进行优化,增加变阻器提高电路的安全性.该教具制作简单、操作方便、演示成功率高、效果明显、安全可靠,可用于开展拓展实验.  相似文献   

9.
在做通电导体在磁场中受力运动的演示实验时,一般用铝导线作为通电导体,由于铝导线的直径小,实验的可见度低,不利于学生对实验的观察。为了增大实验的可见度,有利于学生观察通电导体在磁场中的运动情况,可制作一个空心导体。  相似文献   

10.
一、选择题_一, 1.关于磁场和磁感线的描述,正确的说法是(). A.磁感线从磁体的N极出发,终止于S极 B.磁场的方向就是通电导体在磁场中某点受磁场作用力的方向- C.沿磁感线方向,磁场逐渐减弱 D.同一段通电导体在磁场强的地方受的安培力可能比在磁场弱的 1 地方受的安培力小、  相似文献   

11.
Green cutting has become focus of attention in ecological and environmental protection. Steam is cheap, poilution-free and eco-friendly, and then is a good and economical coolant and lubricant. Steam generator and steam feeding system were developed to generate and feed steam. Comparative experiments were carried out in cutting AA6061-15 vol.% SiC (25 p.m particle size), with cubic boron nitride (CBN) insert KB-90 grade under the conditions of compressed air, oil water emulsion, steam as coolant and lubricant, and dry cutting, respectively. The experimental results show that, with steam as coolant and lubricant, gradual reduction in the cutting force, friction coefficient, surface roughness and cutting temperature values were observed. Further, there was reduction in built up edge formation. It is proved that use of water steam as coolant and lubricant is environmentally friendly.  相似文献   

12.
Oil-soluble stannous naphthenate (SN) is synthesized by using naphthenatic acid and SnO.And its molecular structure is confirmed by IR and multielement oil analyzer (MOA).The tribological performances of the organotin as lubricant additive are evaluated with a four-ball friction and wear tester.These experiments indicate that the wear scar diameter (WSD) and friction coefficient are diminished while the load-carrying capability increased by comparison with that of base oil.The elemental composition of the boundary lubricating film is examined by means of Auger electron spectroscopy (AES).Synergistic effect is found in the load-carrying capability of the complex of SN and sulfured olefin.The analytical results of AES indicate that the good performance of stannous naphthenate is attributed to the formation of a boundary lubricating film containing Sn on the rubbed surface.  相似文献   

13.
Oil-soluble stannous naphthenate (SN) is synthesized by using naphthenatic acid and SnO. And its molecular structure is confirmed by IR and multielement oil analyzer (MOA). The tribological performances of the organotin as lubricant additive are evaluated with a four-ball friction and wear tester. These experiments indicate that the wear scar diameter (WSD) and friction coefficient are diminished while the load-carrying capability increased by comparison with that of base oil. The elemental composition of the boundary lubricating film is examined by means of Auger electron spectroscopy (AES). Synergistic effect is found in the load-carrying capability of the complex of SN and sulfured olefin. The analytical results of AES indicate that the good performance of stannous naphthenate is attributed to the formation of a boundary lubricating film containing Sn on the rubbed surface.  相似文献   

14.
Modeling and analysis of wet clutch engagement characteristics   总被引:1,自引:0,他引:1  
A mathematical model was developed to analyze the characteristics of the wet clutch during engagement. The lubricant squeeze action was simulated with Patir and Cheng average flow model in which the permeability of friction material is taken into account, and the asperity load is calculated according to the Greenwood and Tripp approach. In this model, effects of friction material permeability, applied load and driving velocity on the engagement characteristics of the wet clutch were studied. The results show that friction material with high permeability reduces the film thickness rapidly and increases the torque peak; the applied load increases the asperity contact pressure and the friction torque, and reduces the engagement time; the driving velocity mainly increases the engagement time. The theoretical torque and relative velocity curves agree qualitatively with the experimental ones, which verifies the wet clutch engagement model.  相似文献   

15.
通过试验室试验和工业实验方法,对不同性能的润滑剂,在不同的运动形式及工况条件下所获得的试验数据和结果进行了分析,以寻求润滑摩擦的规律性,分析它的影响因素(如载荷、速度、运动形式、润滑剂性能以及温度等),从而进一步了解和掌握摩擦学特性及不同性能的润滑剂所应用的工况条件。  相似文献   

16.
Micron grade Sn powder, VG32 oil and active pharmaceutical were mixed and the Nanometer Sn lubricant additives were prepared. Nanometer additives with different Sn concentrations were used in Steel-brass Tribo-pair for friction and wear test. The activating method to nano-Sn and surface of brass samples was investigated, and the method to form relatively thick friction coating on samples was discussed. Surface elemental distribution, coating thickness and its surface appearance were analyzed with X-ray photoelectron spectrum (XPS), auger electron spectrum (AES) and scanning electron microscope (SEM) respectively. The result shows that the ultra-thick friction coating (approx 20 μm), with abundant tin and well combined with substrate, has formed on the brass sample. The friction coating revealed superior performance of friction reducing and anti-wear properties. Therefore, the results possess practical significance to self-repair usage on steel-brass tribo-pair in mechanical systems.  相似文献   

17.
By an iteration method, the influence of oil film inertia on piston skirt lubrication in a high speed engine is investigated. By alternately solving the Navier-Stocks equations and the Reynolds equation, the new iteration method can trace the variations of velocity field and pressure field with time. Based on this, the mixed-lubrication model suitable for the piston skirt of high engines is proposed. By introducing the inertia coefficient, the new lubrication model includes the inertia term in oil film. The model can be also used to solve for the lubrication performances of a piston skirt in low or medium speed engines and for lubrication problem in general excluding  相似文献   

18.
The effects of the mechanical factors with applied loads on the tribological performance of refined, bleached and deodorised (RBD) palm stearin (PS) were studied using a four-ball tribotester. All the RBD PS results were simultaneously compared with the additive-free paraffinic mineral oil (PMO). The experiments were carried out using different loads with a constant speed in order to gain a better understanding of the mechanical processes that occurred during the experiment. For each experiment, the temperature was increased to 75 °C and was run for 1 h. In a mechanical system, lubricant plays an important role in reducing wear and friction. PS exists as a semi-solid at room temperature after the fractionation process from oil palm. Due to the increasing rate of pollution to the environment, vegetable oil was chosen as the test lubricant with regard to its biodegradability. Other advantages of vegetable oil are that it is more easily harvestable and non-toxic compared to petroleum-based oil, which made it a suitable candidate. From the experiment, RBD PS is found to have a better friction constraint reduction compared with additive-free PMO.  相似文献   

19.
为解决静摩擦力难以判断的问题,提出了概念判断法、加速度判断法、综合分析法等方法.  相似文献   

20.
求解静摩擦力是物理教学的难点之一。文章探讨了静摩擦力判断的基本途径,力图为静摩擦力的教学解难释疑。  相似文献   

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