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对于判定“如何变化”一类选择题,用“端值法”,常可以化繁为简。例1.如图1,滑片向右移动时,安培表示数: (A)变大.(B)变小.(C)不变. 一般解题思路是,滑片向右移动时连入的R_1减少,导致并联部分的电阻变化,其变化情形经讨论得出结论后,再结合R_3考虑总电阻的变化情形,最后才知道电流强度如何变化;用“端值法”只需分析“极端”情形。设滑片在最右端,则并联部分的电阻为零,此时电路总电阻有最小值即R_3,电路总电流强度为最大值。这表明了这样的趋势,滑片向右移
For the “how to change” type of multiple-choice question, using the “end value method” can often be simplified. Example 1. As shown in Figure 1, when the slider moves to the right, Ampere indicates the number: (A) becomes larger (B) becomes smaller. (C) does not change. The general problem-solving idea is that when the slider moves to the right, it is connected. The decrease in R_1 leads to a change in the resistance of the parallel section. After the changes are discussed and the conclusions are reached, the change in the total resistance is considered in combination with R_3 to finally know how the current intensity changes; the “end value method” only needs to analyze “extreme” "situation. If the slider is at the rightmost end, the resistance of the parallel connection is zero. At this time, the total resistance of the circuit is R_3, and the total current intensity of the circuit is the maximum. This shows the trend, the slider moves to the right