高中物理课讲授“闭合电路的欧姆定律”一节之前要做好一个关键性的演示实验,证明内、外电路的电压之和等于电动势,即ε=U+U′。目前教师习惯的做法是利用工厂生产的现成产品即可调内阻蓄电池演示,多次的实践表明误差十分大,内电压U′比预期的要小得多,小到无法接受。老师们 Before the high school physics lesson “The Ohm’s Law of Closed Circuits” section, we must make a key demonstration experiment to prove that the sum of the voltages of the internal and external circuits is equal to the electromotive force, ie ε=U+U′. At present, teachers are accustomed to using the off-the-shelf products produced by the factory to adjust the internal resistance of the battery demonstration. Many practices have shown that the error is very large, and the internal voltage U′ is much smaller than expected and is unacceptably small. teachers