题如图1,当P由a端滑到b端时,电路中电流表的示数变化情况是()(A)逐渐变大.(B)逐渐变小.(C)先变小后变大.本题答案为C.结论:与P在滑动变阻器的中点时,并联电路的总电阻最大,因而电流表的示数最小;当P从中点向任何一端滑动时,电流表的示数都将 The problem is shown in Figure 1. When P slides from side a to side b, the change of the current meter in the circuit is () (A) gradually becomes larger, (B) gradually becomes smaller, (C) becomes smaller and then becomes larger. The answer to this question is C. Conclusion: When P is at the midpoint of the sliding rheostat, the total resistance of the parallel circuit is the largest, and therefore the current meter is the smallest; when P slides from the midpoint to either end, the current meter will display