试题与答案

物理实验室里有两只小灯泡L1、L2,其中L1上标有“6V3W”,L2上标有“9V

题型:问答题

题目:

物理实验室里有两只小灯泡L1、L2,其中L1上标有“6V 3W”,L2上标有“9V 3W”的字样,小聪、小明、小慧对这两只灯泡接在同一个电路中的亮度进行了猜想:

小聪认为一定是L1较亮,因为工作时通过L1的电流大;小明认为一定是L2较亮,因为L2的额定电压大;小慧认为一定是两灯一样亮,因为它们的额定功率相同.

为了验证谁的猜想正确,他(她)们进行了如下实验:

(1)将L1、L2两灯按图甲并联接在6V的电源上,用电流表A1、A2分别测出通过两灯的电流,填入图表,同时观察比较两灯的亮度,发现L1比L2亮;

(2)将L1、L2两灯按图乙串联接在6V的电源上,用电压表V1、V2分别测出L1、L2两端的电压,填入下表,同时观察比较两灯的亮度,发现L2比L1亮.

请你根据图乙所示的电路图,用笔画线代替导线,在图丙中将V2接入电路.

电表A1A2V1V2
示数0.50A0.22A1.85V4.15V

分析论证:

(1)图甲中,两灯电压相同,通过L1的电流较大,此时L1的实际功率比L2的大,所以L1比L2亮;

(2)图乙中,______,所以L2比L1亮;

(3)由此可知,三位同学的猜想都是片面的,决定灯泡亮度的应是灯泡工作时的______.

答案:

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