初中物理课本是在引入电阻概念以后,再阐明用导体两端的电压跟通过导体的电流强度的比值来表示导体的电阻的。我们在教学实践中对这部分内容作了调整,在第五节研究“电流强度跟电压的关系”的实验时,就引进了电压跟电流强度的比值,用这个比值得出导体中的电流强度跟这段导体两端的电压成正比的结论。这样,不但为电阻概念的引入作了坚实的铺垫,而且突出了用比值来定义(表示) In junior high school physics textbooks, after the concept of resistance was introduced, the resistance of the conductor was expressed by the ratio of the voltage across the conductor to the current intensity through the conductor. We have adjusted this part of the teaching practice. In the fifth chapter, when we studied the experiment of “the relation between current intensity and voltage”, we introduced the ratio of voltage to current intensity, and used this ratio to derive the current intensity in the conductor. This is in direct proportion to the voltage across the conductor. This not only lays a solid foundation for the introduction of the concept of resistance, but also highlights the use of ratios to define (indicate)