本模块的主要教学内容是电介质以及静电能两部分。大家对电介质这部分内容相对陌生点,感觉学习有一定的难度。其实在之前学习的知识基础上,学会将已经学到的静电场基本规律的知识来分析场对电介质作用的后果,以及电介质对场作用的响应,学习起来就不会觉得太困难了。通过对处在静电场中导体的研究,我们一方面了解了当导体达到静电平衡时导体的性质,同时也学习了如何研究场对物质作用的这类问题的方法,这对于学习处在静电场中的电介质的性质是有帮助的。虽然研究的对象不同,但是研究的方法有共同之处。整个模块分四节课,第一课是介绍电介质的极化,与导体不同之处是,电介质内基本上没有可以移动的自由电子,但是不影响组成电介质的原子分子中的电荷受电场的作用而发生局部的小范围的运动,因此这里的一个非常重要的基本问题是考察组成介质的原子分子作为电偶极子在电场作用下的行为即电介质的极化。重点研究介质的是在电场作用下达到平衡后的性质。所以总体来讲,第一课学习的重点是了解极化机制,如何确定因为极化产生的极化电荷分布,以及这些计划电荷对电场的影响。第二课是第一课内容的通过例题帮助同学们了解如何确定计划电荷分布和求出极化电荷产生的场。第三课的主要内容是讨论有介质存在时电场的性质,即给出了有介质时场的高斯定理和环路定理。第四课主要的内容是电场能量和边界条件,电场能量涉及到静电场的能量是如何聚集起来的,由此讨论到导电体系的自能、相互作用能和总静电能。在讲解相互作用能时,同学们会感觉公式多,理解起来有一定的难度。实际这里采取的是归纳法,从两个点电荷系统出发,逐步推演,推广到多个点电荷系统。从离散的点电荷组系统的相互作用能通过求极限,推广到连续带电体的总静电能,最后讨论了带电体系静电能与电场能量的关系。这样的讨论展示了物理学研究问题的一种方法,是值得借鉴的。所以学习这部分知识,重点在于理解;关于边界条件问题,实际上是在不同介质的交界面上运用高斯定理和环路定理得到的结果。电场能量与边界条件与静电场的基本规律这些知识点互相关联,会出现在综合分析的问题中。本模块也有一些练习题,主要注重对概念的理解,同学们应该在规定的时间内完成,希望大家作为自我测试,独立完成,如何评分详见评分标准。 除了课后测试题外,本周可参考《大学物理通用教程》电磁学中与电介质相应的题目不多,是《大学物理通用教程》电磁学 p90 2-12、13、14、15、16、17、18、19、20、21。 here
Peking University is determined to make its education openly accessible to students in China and around the world. With over 3000 faculty members, Peking University offers excellence in teaching and learning.
Founded in 1898, Peking University (PKU) was the first national comprehensive university in China. For the past 115 years, with its hundreds of thousands of outstanding alumni, Peking University has made prominent contributions in the humanities and sciences to further China's prosperity and progress.
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