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例1 如图1所示,电源电压不变,当滑动变阻器的滑片P向右移动时,电流表、电压表的示数如何变化?电灯的亮度如何变化? 解析:电压表测电灯两端的电压,当滑动变阻器的滑片P向右移动时,变阻器连入电路的电阻变大,整个电路中电阻变大,根据欧姆定律电路中的电流变小,电灯两端的电压也变小,此时电灯消耗的电功率变小,电灯的亮度变暗. 方法指导:滑动变阻器的滑片移动时,电路中多个物理量发生变化,引起变化的原因多由
Example 1 As shown in Fig. 1, the power supply voltage does not change. How does the current meter and voltmeter change when the sliding polarizer P moves to the right? How does the brightness of the lamp change? Analyze: The voltmeter measures the voltage across the lamp. When the slide P of the sliding rheostat moves to the right, the resistance of the varistor circuit is increased and the resistance in the entire circuit becomes larger. According to the Ohm’s law, the current in the circuit becomes smaller, and the voltage across the lamp becomes smaller. The electric power consumed becomes smaller and the brightness of the lamp becomes darker. Method Instructions: When the slider of the sliding varistor moves, multiple physical quantities in the circuit change, and the cause of the change is caused by many reasons.