transfromer power loss一問

1. 由於導線有一定的電阻，所以電流流過時會不斷有電壓的降低。所以並不可以用P = V^2 / R來計的，因為你不知道V是什麼。

相反，在導線上的電流值是固定的，這可以用兩點的電勢差(potential difference)計算，所以可以計算P = I^2R。


2. 輸出電的功率P = IV

如果將傳輸時的電壓提高(V加大)，便可令傳送電流值減低(I減低)。以第一題的理由，P = I^2R，I減少，Power loss便可以減少了。

你所指V的減少是兩點的電勢差。注意有很多單位的，所以小心。

Are you asking for the power loss in a transformer or the power loss in a transmission cable?
They have different interpretations.

2009-02-22 01:01:48 補充：
In general, the two equations P=I^2.R and P=V^2/R are the same, as one can be deduced from the other using Ogm's Law. No matter which equation is used, you will get the same answer.

2009-02-26 13:59:25 補充：
Please refer to my answer given to a similar question on this forum.
http://hk.knowledge.yahoo.com/question/question?qid=7009022301686