什麼是正極?什麼是負極?

正極是收電的(吸)
負極是放電的(出)
導體有自由電子，所以可以導電。
絕緣體沒有自由電子，所以不能導電。
半導體和超導體都是導體，而後者的電阻近乎零，所以叫超導體。

正極 positive pole is the place where electron go into. 負極 negative pole is the place where electrons are going out. Therefore, electrons go from negative pole to negative pole. BUT remember, current flow from positive to negative.

導體 conductors can conduct electricity as they have mobile ions or mobile electrons.
絕緣體 Insulators cannot conduct electricity as they have no mobile ions or electrons.
PS All objects can conduct electricity if the voltage is high enough.

超導體 Super conductors have very small resistance, it has good electrical conductivity.
半導體 Semiconductors. When temperature increase, the resistance decrease which is not so common and does not obeys ohm's law. Silicon is an example.

2006-11-06 18:44:49 補充：
Super conductors must be used in extremely low temperature. The operating cost is therefore very high.

因為絕緣體沒有電!