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如图1,电源电压12伏保持不变,小灯泡 L上标有“8V4W”字样,滑动变阻器 R_1的阻值范围是0—64欧姆,电阻 R_2 为64欧姆,问:(1)S_1、S_2都断开时,小灯泡 L 恰能正常发光,滑动变阻器 R_1接入电路的电阻是多大?(2)S_1闭合,S_2断开时,移动滑动变阻器的滑片 P,当灯 L 的实际功率为1瓦时,电流表 A_1示数多大?R_2消耗的功率多大?(3)S_1、S_2都闭合,当整个电路消耗的电功率最小时,电压表 V 示数多大?干路中的电流强度多大?
As shown in Figure 1, the power supply voltage remains unchanged at 12 volts, the small bulb L is marked with “8V4W”, the resistance of the sliding rheostat R_1 is 0-64 ohms, and the resistance R_2 is 64 ohms. Q: (1)S_1 When both S and S_2 are off, the small light bulb L can just emit light normally. What is the resistance of the sliding rheostat R_1 into the circuit? (2) When S_1 is closed, when S_2 is disconnected, the slide P of the sliding rheostat is moved, when the lamp L is actually When the power is 1 watt-hour, how large is the current meter A_1? How much power is consumed by the R_2? (3) S_1 and S_2 are all closed. When the electric power consumed by the entire circuit is the smallest, how large is the voltmeter V? How big is the current in the trunk? ?