“电能的输送”教学设计及反思

本课选自人教版高中《物理》新课标教材·选修3-25.5电能的输送一节,此课与义务教育课程标准试验教科书《物理》八年级下册6-8单元的知识相关联。在初中阶段教师讲授的是部分电路的欧姆定律,而此课是针对全部电路的欧姆定律的讲解,在此基础上全面、细致地分析和解决电学方面的知识,为初中教师教学进一步提供了课程资源.     

跳出物理解题的思维陷阱

人的思维一般都具有一定的惯性,往往会因此而形成思维定势。思维定势既可以把思维引向纵深,但同时也容易使人钻牛角尖,走入死胡同,显得狭隘、死板、固执。下面结合几道题谈一谈思     

机械式功率回收液压马达性能试验平台的设计

针对大功率液压马达的性能测试,设计了基于机械式功率回收液压马达性能检测试验平台。分析其液压系统回路的工作原理以及硬件组成;以试验平台的液压回路为研究对象,重点阐述其流量与转矩的匹配关系、功率回收、加载以及控制等关键问题。对整个试验平台的液压系统及控制系统进行现场试验,在将试验结果与理论分析结果进行对比分析后,可以看出,该试验平台达到了预期的对马达进行性能测试以及实现功率回收的效果,节能效果明显。     

额定功率与实际功率

一、概念辨析1.额定功率是用电器正常工作时的最大输出功率,而实际功率是电流通过用电器时真正消耗的功率.例如“220V,40W”的灯泡,它的额定功率是“40W”,它表明这个灯泡正常工作时的最大输出功率是“40W”,超过这个数值,灯泡就可能被烧坏.而这个灯泡的实际功率要视具体的工作环境而定.例如在“220V”的电压下,这个灯泡的实际功率就是“40W”,在“110V”的电压下,这个灯泡的实际功率就只有“10W”.     

小议滑动变阻器的三种接法

滑动变阻器在电路中有三种常见的接法,即限流式、分压式和并联式接法.对应于这三种接法,滑动变阻器对电路的控制和影响各不相同.     

用导数速解物理题

从八年前高考数学新课程卷开始,导数逐渐成为数学高考的热点.在物理中,运用导数解题的试题较少.然而,运用导数求解某些物理问题,很便捷,应予重视.     

Decomposing apparent power and losses in distribution systems with nonlinear loads

The definition of reactive power for non-sinusoidal conditions is a controversial issue. The mathematical treatment of nonlinear loads in power systems is also unsettled. This paper starts with the decomposing of apparent power in,the cases of linear and nonlinear loads. When harmonics are present, apparent power is composed of active power, reactive power, and disturbed reactive power. Linear element can be defined as the element without disturbed reactive power. This definition is based on a practical engineering concept which can separate the contribution from the apparent power into utility-duty part and custom-duty part. The field investigation of home-used facilities was conducted. Also the data acquisition in the 0.4 kV distribution systems was completed. Moreover, the loss increase due to the nonlinear loads was estimated. Nonlinear loads can be a dominant effect with respect to reactive power and power factor. Field data from a number of nonlinear load types indicate that the disturbed reactive power can cause significant losses in utility supply systems.     

TDD-CDMA 系统中基于业务统计的联合功率控制算法

An important feature of the traffic in mobile networks is burstiness. Drawbacks of conventional power control algorithms for time division duplex （TDD）-code division multiple access （CDMA） systems are analyzed. A joint power control algorithm based on service factor is presented to address the TDD-CDMA mobile services in the burst mode according to the Markov modulated Bernoulli process. The joint power control equation is derived. A function model is developed to verify the new algorithm and evaluate its performance. Simulation results show that the new power control algorithm can estimate interference strength more precisely, speed up convergence of power control, and enhance power efficiency and system capacity. It is shown that the proposed algorithm is more robust against link gain changes, and outperforms the reference algorithms.     

电功率图象信息题解析

有关电功率的图象信息题是近年来中考常见题型之一,现例析如下:例1 如图,小明利用标有6V 6W的灯灯 L_1和6V 3W的灯泡 L_2进行实验.如图甲所示:A、B分别为通过灯泡 L_1和 L_2中的电流随两端电压变化关系的曲线.现将两灯连入图乙所示电路中,使其中一个灯泡正常发光,电路中电流表示数为____,电压表示数为____,电路消耗的总功率为____.     

关于功率计算式的讨论

在进行功率的计算时,往往由于对公式P=W/t和P=Fvcosα的不能正确理解,而导致计算错误,下面例析这两个式子在应用时应注意的问题。