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题:将“220V 100W”的白炽灯与总电阻为121欧的变阻器串联起来,接到220伏的电源上(如图1),调整变阻器的阻值时,可使电灯的功率在多大的范围内变化?分析:电灯和变阻器串联后,当滑片 P 向右移动时,变阻器连入电路中的电阻值在变小,整个串联电路的总电阻变小,由欧姆定律I=U/R 可知,串联电路中的电流变大,灯泡两端电压变大,由 P=U~2/R 可知,灯泡的功率变大.当滑片移至最右端时,灯泡的电功率达最大值.同样当滑片向左移动时,变阻器连入电
Question: Connect the “220V 100W” incandescent lamp with a varistor with a total resistance of 121 ohms and connect it to a 220 volt power supply (Figure 1). Adjust the resistance of the rheostat to make the lamp’s power much larger. The range of change? Analysis: After the lamp and varistor are connected in series, when the slide P moves to the right, the resistance value of the varistor connected to the circuit becomes smaller, and the total resistance of the entire series circuit becomes smaller, by Ohm’s law I=U/ R can see that the current in the series circuit becomes larger and the voltage across the lamp becomes larger. It can be seen from P=U~2/R that the power of the lamp becomes larger. When the slider moves to the rightmost end, the electric power of the lamp reaches a maximum value. Also when the slider moves to the left, the varistor is connected to the power