论文部分内容阅读
前一段时间,笔者有幸到城区一所中学听初中物理研讨公开课,内容是《欧姆定律的应用》.在做测小灯泡的电阻实验时,实验桌上所给的器材是电池盒(两节干电池)、小灯泡(标有“2.5V0.3A”字样)、电流表、电压表、滑动变阻器、开关、导线等.学生分组实验后,教师请一组学生汇报数据,在投影上打出结果如下表.分析表中数据,得出灯泡的电阻不是一个定值,而是随电压的增大而增大,原因是灯丝电阻与温度有关的结论.乍看上去,并没有什么,仔细想想有几个疑问:(1)灯泡的额定电压是2.5V,教师展示的最大电压为1.3V,灯泡在几乎不发光的情况下测得的电阻,能得出灯泡电阻与温度有关这么重要的结论吗?(2)为什么放着实验桌
Some time ago, I was fortunate enough to go to a secondary school urban junior high school physics seminar open class, the content is “ohm’s law application.” When doing small bulb resistance test, the experiment table is given equipment is the battery box (two Dry cell), small bulb (marked with “2.5V0.3A”), ammeter, voltmeter, sliding rheostat, switch, wire, etc. After grouping students, the teacher invited a group of students to report the data and put the result on the projection Analysis of the data in the table shows that the resistance of the bulb is not a fixed value but rather increases with increasing voltage due to the fact that the filament resistance is temperature-dependent. At first glance, there is nothing to think about There are a few questions: (1) bulb rated voltage is 2.5V, the teacher shows the maximum voltage of 1.3V, light bulb in the case of almost no light measured resistance can be drawn bulb resistance and temperature is so important conclusion Why? (2) Why the experimental table