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一、金属电阻率和温度关系的实验按照课本上的装置(初中物理第二册图2-25)加热时间长,实验现象不明显。因为在一般学校实验室条件下很难办到用一根直径非常细的长铁丝,均匀绕成螺线管(每圈间都不能碰),并使它的电阻值能达到几十欧姆。这样,因为铁丝本身电阻不大,即使加热后电阻率变化较大,电阻值的变化仍非常小。所以电路中电流的变化很不显著。我们采用普通白炽灯中的钨丝来代替铁丝效果甚佳。虽然钨在温度每升高1℃电阻率的增加量与原来值的比是0.0045,较铁略小,但一个“220v,40w”白炽灯泡灯丝的电阻值(不发光时)可达
First, the metal resistivity and temperature experiments according to the textbook device (junior high school Physics Volume II Figure 2-25) heating a long time, the experimental phenomenon is not obvious. Because in the general school laboratory conditions is difficult to do with a very thin diameter wire, even into a solenoid (can not touch each turn), and its resistance can reach tens of ohms. In this way, because the wire itself is not very resistant, even if the resistivity changes greatly after heating, the change of the resistance is still very small. So the current in the circuit changes is not significant. We use ordinary incandescent tungsten filament instead of the wire is very good. Although the increase in resistivity per 1 ° C increase in tungsten compared to the original value is 0.0045 and slightly less than that for iron, the resistance of a “220v, 40w” incandescent filament filament (when not emitting light)