in which什么时候=where？

只有在定语从句中是等价的.
例如:把这两句话合成一句定语从句1.Is this the factory? 2.Your father works there.-----Is this the factory that/which your father works in?(there相当于in the factory,即2句本身为Your father works in the factory)另外,也可以变换成Is this the factory in which your father works?
in which=in the factory=where,最后变为Is this the factory where your father works?
语法点:主要是定语从句出现:
介词+which,当表示地点时介词+which可变为where
当表示时间时介词+which可变为when
练习:<1>This is the place ( ) I was born.
<2>This is the place ( ) I used to visit.
分析:第一句中born和the place的关系是born in the place,构成介词加名词的形式,空格处可以填 in which,而介词+which,当表示地点时介词+which可变为where,即在此处in which 表我出生的地点,所以可换成where.(此处in which=where)This is the place ( in which/where ) I was born.;第二句中visit和the place的关系是visit the place ,不需要介词,所以可以填表示物的which或表示人或物的that.This is the place ( which/that ) I used to visit.
自己总结的,不知能否看懂.祝你好运!

你记住，in which永远是正确的，where则不一定