Question

This is one of the means()the electric energy is conducted from one place to another

为什么填by which 不填by that

Answer 1

这是一个定语从句,one of the means是先行词,the electric energy is conducted from one place to another是从句,你看先行词在从句当中做的是状语成分,通过这种方法,(by与means是固定搭配)which 和 that 叫关系代词.
定语从句当中,关系代词前面有介词,则只能用 prep.+which(表物)或prep+whom(表人) 这是语法.

Answer 2

好像没by that这种用法，要么就直接添that，不用加by. which表选择。前面有个one of the means，which就是指one of the means的其中一种。从the electric energy is conducted from one place to another就是说明这一种mean.非限定定语从句。好像是这样吧！

Answer 3

关系代词前面有介词时，只能用which，不能用that

Answer 4

that 可有可无，没有确实指代的东西时用，这里有确实指代的东西，用which.
that前一般没有先行词（by）