電壓和電流

在一個實體的電器，即已經做為成品的電器，如一個燈泡，電壓越高，電流就越大。
在設計中的電器，在構思和設計途中，輸入的電壓可以越高，在相同功率的原則下，電流就可變小越。



2009-10-18 00:37:28 補充：
打錯更正：在相同功率的原則下，電流就可變得越小。

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Most materials that obey Ohm's Law (i.e. ohmic materials) will have the current that flows through them proportional to the applied voltage.

Only some special materials have negative resistance, i.e. an increase of voltage decreases the current.One such material is a carbon fibre composite material discovered in 1998 by US scientists (see the web-page below).

http://physicsworld.com/cws/article/news/3204

Nevertheless, some specially designed circuits could act as a component that behave to have negative resistance.

http://en.wikipedia.org/wiki/Negative_resistance