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题目如图所示,电源电压保持不变,电阻 R 是定值电阻.在 a、b 两接线柱上接一个标有“6V 2W”的灯泡 L_1,闭合开关 S,灯泡恰好正常发光;如果在 a、b 两接线柱间换一个标有“6V 3W”的灯泡 L_2,闭合开关 S 后,这只灯泡消耗的功率A.小于3W B.等于3WC.大于3W D.不能确定错解1 由于当灯泡接入电路中时,灯泡的电压为6V,灯泡正常发光,当接入 L_2时,仍然正常发光,此时功率为3W,选答案 B.分析这种错误的原因是没有注意电路的变化过程.在接灯泡时,电路中的电阻发生变化,电流也发生变化,灯泡的电压不再是6V,因
The problem is shown in the figure, the power supply voltage remains the same, and the resistance R is a fixed value resistor. A lamp labeled L1 is marked on the terminals a and b, and the switch S is closed. The light bulb just glows normally. If you replace the lamp L_2 marked with “6V 3W” between the terminals a and b, the power consumed by the lamp after the switch S is closed is less than 3W. B. It is equal to 3WC. It is greater than 3W. D. Uncertain Solution 1 Because when the bulb is connected to the circuit, the voltage of the bulb is 6V, and the bulb emits light normally. When it is connected to L_2, it still emits light normally. At this time, the power is 3W. Select the answer B. The reason for analyzing this kind of error is no attention. Changes in the circuit. When the light bulb is connected, the resistance in the circuit changes and the current changes. The voltage of the light bulb is no longer 6V.