变压器一、二次侧电压有效值之比可以近似地认为等于（        ）之比。

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SQL Error: select id,body,options from ***_enewstiku_ where sourceid='68477' and id < 4421302 and id<>'4421302' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku_ where sourceid='68477' and id > 4421302 and id<>'4421302' order by id asc limit 5