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一、利用实际问题加强对“交变电流有效值”的考查例1 图1中a为某型号电热毯的电路图,将电热丝接在u=156sin120πtV的电源上, 电热毯被加热到一定温度后,由于P的作用使输入的正弦交流电仅有半个周期能够通过,即电压变为图b所示波形,从而进入保温状态, 则此时交流电压表的读数是( )
First, the use of practical issues to strengthen the “effective value of alternating current” test Example 1 a in Figure 1 for a certain type of electric blanket circuit diagram, the electric heating wire is connected to the u = 156sin120πtV power supply, the electric blanket is heated to a certain temperature Due to the effect of P, the input sinusoidal alternating current can only pass through half a cycle, that is, the voltage changes to the waveform shown in Figure b, so as to enter the keep-warm state, then the AC voltmeter reading is ()