點解短的wire同理長的wire的resistance高D？

金屬由一群依一定規則排列原子構成，每顆原子均有一層（或多層）由電子組成的外殼。這些在外殼的電子能脫離原子核的吸引力而到處流動，是金屬能導電的主要原因。當金屬兩端產生電勢差（即電壓）時，電子因電場的影晌而作規則的流動，是為電流。在現實中，物質的原子排列不可能為完全規則，因此電子在流動途中會被不按規則排列的原子打散，是為電阻的來源。

1.高溫加速電子運動，增加電子被打散的機會，故熱的物體電阻較高。
2.橫切面面積大的金屬有較多空間予電子流動，故電阻較小。
3.電子橫過較長的金屬時一般會發生較多的碰撞，故長的金屬電阻較大。

2008-03-09 16:49:01 補充：
A metal consists of a lattice of atoms, each with a shell of electrons. This can also be known as a positive ionic lattice. The outer electrons are free to dissociate from their parent atoms and travel through the lattice, creating a 'sea' of electrons, making the metal a conductor.

2008-03-09 16:49:16 補充：
When an electrical potential difference (a voltage) is applied across the metal, the electrons drift from one end of the conductor to the other under the influence of the electric field.
Near room temperatures, the thermal motion of ions is the primary source of scattering of electrons

2008-03-09 16:49:24 補充：
(due to destructive interference of free electron wave on non-correlating potentials of ions) - thus the prime cause of metal resistance. Imperfections of lattice also contribute into resistance, although their contribution in pure metals is negligible.

2008-03-09 16:49:39 補充：
The larger the cross-sectional area of the conductor, the more electrons are available to carry the current, so the lower the resistance. The longer the conductor, the more scattering events occur in each electron's path through the material, so the higher the resistance.

2008-03-09 16:50:39 補充：
Different materials also affect the resistance.
因為字數過多的問題..
所以分開佐5舊- -
再有開題我都幫唔到你啦- -

不對吧，長點的電線比短的resistance應該多D，你是不是在說短路時？