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例1:如图,灯 L 阻值为12欧,R 阻值为4欧,C 为滑动变阻器的中点,当开关 S 与 a 相连,滑片 P 位于 c 点时,电压表 V_1和 V_2示数之比为2:1;当开关 S 与 b 相连,滑片 P 仍位于 c 点时,灯 L 刚好正常发光;当滑片 P 滑向最右端 B 点时,电流表示数为0.4安,求滑动变阻器最大阻值R_(AB),电源电压 U 和灯泡 L 额定电压 U_L?解:根据题意可列方程组
Example 1: As shown, the lamp L has a resistance of 12 ohms, R has a resistance of 4 ohms, and C is the midpoint of the sliding rheostat. When the switch S is connected to a and the slide P is at point c, the voltmeters V_1 and V_2 show The ratio of the number is 2:1; when the switch S is connected to b and the slide P is still at the point C, the lamp L just glows normally; when the slide P slides to the rightmost point B, the current expression is 0.4 A. Sliding rheostat maximum resistance R_(AB), supply voltage U and bulb L rated voltage U_L? Solution: According to the problem equations