题目

—I had butterflies in my stomach before I gave that talk. —I __________nervous too if I had been in your shoes. A . was B . would be C . had been D . would have been 答案：D调光台灯上有一个相当于滑动变阻器的旋钮，调节旋钮可改变台灯的明暗．为了研究电功率的变化规律，小红设计了如图所示的电路，用标有“3V”的小灯泡L接在电源电压为4.5V的电路中进行实验研究，实验数据填入下表：实验次数12345678接入电路的变阻器阻值（Ω）13579111315　　电压表的示数　（V）0.451.141.601.962.252.482.662.81　 电流表的示数　（A）0.450.380.320.280.250.230.200.19　 电路的总功率　（W）2.031.711.441.261.131.010.920.84　 变阻器的功率　（W）0.200.430.510.550.570.550.530.52（1）请根据题意连接好电路图1．（2）根据图2表中的数据可知，实验时变阻器滑片P的滑动方向是______（向左、向右）．当L两端的电压为L的额定电压时，通过灯泡L的电流如图1所示，灯泡的额定功率是______W．（3）研究发现当变阻器的电阻调大时整个电路消耗的电功率______．（增大、减小）．（4）小红将变阻器消耗的功率与变阻器阻值的变化画成如图2曲线．据此可知______．