库仑定律适用条件的探析

库仑定律是高中物理的基础知识和重点知识,而其适用条件则是教学中的难点且容易被忽略的环节.本文运用形象、直观的物理模型来分析、阐述库仑定律成立的3个条件,包括静止与相对运动条件、点电荷条件和真空条件,有利于深化对库仑定律物理本质的理解以及促进学生严谨物理思维的建立.     

Preparation, Morphology Transformation and Magnetic Behavior of Co3O4 Nano-Leaves

A series of cubic phase Co3O4 nano-leaves were prepared via a combined approach of solution reaction and calcination. According to x-ray diffraction and electron microscopy, we find that the Co3 04 grain size increases with calcination temperature. This can induce many gaps in the products. M-T and M-H magnetization measurements reveal the typical antiferromagnetie behavior of nano-leaves. The effective moments of the samples prepared at 300, 400 and 500℃ are 5.6, 5.8 and 5.7μB per formula unit （FU）, respectively, larger than the bulk value of 4.14 μB/FU.