求一端口的等效电阻时，用外施电压法的电路为（    ）。

试卷相关题目

SQL Error: select id,body,options from ***_enewstiku_ where sourceid='68474' and id < 4421079 and id<>'4421079' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku_ where sourceid='68474' and id > 4421079 and id<>'4421079' order by id asc limit 5