题目

两根材料相同的均匀导线x和y,x长为L,y为2L,串联在电路中,沿长度方向电势变化如图所示,则x,y导线的横截面积之比为(                                              )                                                                                                                                                    A. 2:3         B. 1:3  C. 1:2       D. 3:1                                                                                                                          答案:B
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